How many btu to heat 1000 sq ft? How many square feet will 30,000 BTU heat? You can get more accurate answers thourgh our BTU heating calculator.
Our goal is to help you determine the right size furnace/heater for your heating requirements. It is based on the needed heating BTU per square foot for most homes and your climate.
Our heating BTU calculator takes those very important factors into account, so, for example, if you have a question like, “how many BTU do I need toheat 1,500 square feet? The quick answer is60,000-80,000 BTUsbased on different climate zones.
The BTU per square foot heating rule of thumb varies widely based on your climate and the size of the house or space you want to heat.
Content Navigation
- How Many BTU of Heating Per Square Foot Do I Need?
- Heating BTU Calculator
- Heating BTU Calculator
- Heating Btu Calculator
- Calculate heating BTU needed in four easy steps.
- Chart of Recommended Heating BTU Per Square Foot
- How Many Square Feet Will 4,000 – 80,000 BTU Heat?
- BTUs: Definition and Ratings
- How Many BTU Do Furnaces Make? Standard Boilers?
- What About Wood Stove/Boilers and Combi Boilers?
How Many BTU of Heating Per Square Foot Do I Need?
That’s an important question to get a right answer to. A furnace or space heater that is too small won’t adequately heat your home on the coldest winter days. Rooms furthest from the heater might become uncomfortably cool spots in your house.
A furnace that is too large will waste energy and create warm spots at grates near the furnace before the cycle ends.
The generally accepted BTU per square foot heating rule of thumb ranges from 30 BTU to 60 BTU per square foot. That’s a wide difference, essential one furnace being twice as large as the other, so the size factors are discussed to help you narrow down the right BTUs needed for your home.
This list showing heating BTU per square foot is taken from our PickHVAC Furnace Ultimate Guide:
- Zones 1 & 2 (hot): 30-35 Btu/sq. ft.
- Zone 3 (warm): 35-40 Btu/sq. ft.
- Zone 4 (moderate): 45 Btu/sq. ft.
- Zone 5 (cool): 50 Btu/sq. ft.
- Zone 6 (cold): 55 Btu/sq. ft.
- Zone 7 (very cold): 60 Btu/sq. ft.
The Zones are shown in the map below. There are factors other than climate, and they are used in our heating BTU calculator below to give you the most accurate information.
Example: With 75,000 BTU heater, you can heat a 2,500 sq ft house in Florida. If you’re living in New York, a 75,000 BTU furnace would only heat a 1,500 sq ft home.
Heating BTU Calculator
OK, there is more information below.
Let’s start with this very useful map. It was developed by the International Code Council / International Energy Conservation Code and adopted by the US Department of Energy’s Office of Energy Efficiency & Renewable Energy.
We mention that to represent it as accurate and very useful for our purposes.
Heating BTU Calculator
See local cost of
30,000 BTU Heating Unit
Calculate heating BTU needed in four easy steps.
1. Climate Zone: Find your location on the map. Pro tip: If you’re on or near the border between Zones, choose the higher number/cooler Zone.
2. Home Size: Enter the square footage of your home. If you don’t know it, the information might be found on a blueprint or house drawing, in closing documents or similar. If you don’t have any of those, the easiest way to determine it is to measure rectangles within your home – multiplying width x length for each if there are more than one – and adding their totals.
3. Insulation: There are two keys to insulation – How well your home is sealed and the type and thickness of the insulation. In terms of being sealed, is your home’s exterior covered in house wrap like Tyvek? It’s also called vapor barrier. It is now code, so if your home doesn’t have it, vapor barrier/wrap will have to be installed the next time you replace the siding.
Are the windows and doors newer and in good condition? If you answer “yes” to the house wrap and window/doors questions, then choose Good or Average in the Insulation box. If you don’t know, if your home is older and hasn’t been remodeled, or if you can feel drafts coming in around windows and doors, choose Poor.
Money Saving Tip:Adding attic insulation to an attic that is inadequately insulated is the #1 best way to lower your heating bills and get the best return on investment. In fact, the prestigious Remodeling Magazine annual survey consistently shows that attic insulation has a 105% to almost 120% return on investment (Cost vs. Value). In other words, the money spent will be quickly gained back through lower energy bills.
The image below shows how much attic insulation your home should have.
4. Sun Exposure: Climate and the trees around your home factor into this box. If your home is surrounded by tall trees that shade the walls and the roof – and few are – then choose Heavily shaded. Most homes, in this regard, are either Average or Very Sunny.
But “Very Sunny” means something very different in Denver (245 days with sun) than it does in Portland, Oregon (142 days with sun), even if there are no shade trees around the house. Therefore, consider the map below. The deeper the color, the more sunny the climate. In Minnesota, a home with no shade would still only be Average for sun exposure, for example.
Make your choice and enter data for each box, and let the heating BTU calculator do the work.
Here is an example how to use the above calculator:
Let’s say you have a 2,500 sq ft two-story home in Chicago. Your house was built in 2005 with a “good insulation”. You should choose “Average Sun Exposure” and “Zone 5” based on the Climate Zone Map and Sun Exposure Map.
After you enter all the data, you will get 90,000 BTUs from the calculator.
Chart of Recommended Heating BTU Per Square Foot
This chart begins small – space heater size, not furnace size – and progresses to homes in the average to large size category. You can use it to answer the common questions like:
- How many btu for 600 sq ft? It’s around 30,000 BTU.
- How many btu do I need to heat 1,500 square feet? It’s 70,000 – 80,000 BTU.
- What size furnace to heat 2,000 square feet? You need a 90,000-110,000 BTU furnace.
- How many btu do I need to heat 3,000 square feet? 150,000+ BTU furnace is a better option.
| Room/Area Size | Heating Capacity(BTU) | Examples |
|---|---|---|
| 100 sq ft | 4,000-6,000 BTU | 10x10 room, 10x12 room, Small den or office |
| 200 sq ft | 9,000-11,000 BTU | 10x20 room, 12x12 room, 15x15 room |
| 300 sq ft | 12,000-16,000 BTU | Efficiency apartment. 12x24 garage |
| 400 sq ft | 18,000-22,000 BTU | 20x20 room or garage |
| 500 sq ft | 22,000-27,000 BTU | Studio/1-bedroom apartment, Tiny house |
| 600 sq ft | 27,000-33,000 BTU | 20x30 room, 24x24 garage |
| 700 sq ft | 31,000-38,000 BTU | 24x30 garage, 1 or 2-bedroom townhouse |
| 750 sq ft | 34,000-41,000 BTU | 26x30 garage, 1 or 2-bedroom townhouse |
| 800 sq ft | 36,000-44,000 BTU | Small home, 2-3 bedroom apartment |
| 900 sq ft | 40,000-49,000 BTU | 30x30 garage |
| 1,000 sq ft | 45,000-55,000 BTU | Small home, 2-3 bedroom apartment |
| 1,200 sq ft | 55,000-65,000 BTU | 30x40 garage, 3 bedroom townhouse |
| 1,300 sq ft | 59,000-71,000 BTU | Small/Average home, large apartment |
| 1,400 sq ft | 63,000-77,000 BTU | Small/Average home, large townhouse |
| 1,500 sq ft | 68,000-82,000 BTU | 40x40 garage, average home |
| 1,600 sq ft | 72,000-88,000 BTU | Average home, large townhouse or home addition |
| 1,700 sq ft | 77,000-93,000 BTU | Average home, large townhouse or apartment |
| 1,800 sq ft | 81,000-99,000 BTU | Average home, large townhouse or apartment |
| 2,000 sq ft | 90,000-110,000 BTU | Average home, large townhouse, guest house |
| 2,200 sq ft | 100,000-120,000 BTU | Average home, 4-bedroom apartment |
| 2,400 sq ft | 108,000-132,000 BTU | Average to large home, very large townhouse |
| 2,500 sq ft | 113,000-137,000 BTU | Average to large home, very large townhouse |
| 3,000 sq ft | 135,000-165,000 BTU | Large home, one zone in a very large home |
At some point, depending on the climate, you have to begin to think about more than one heating device – furnace, boiler, heat pump, etc., for your home. You can still use this chart for very large homes by considering the size of the zones in your home.
For example, if the bedroom and office area zone is 1,800 square feet and the living areas and kitchen are 2,400 square feet, add together the recommended BTUs for each. You’ll need between about 180,000 and 280,000 total BTUs for your home based on the climate and house factors considered in the calculator.
Pro Tip:For smaller rooms/zones/apartments, aductless mini split heat pump is another really good option. They’re efficient and come with potential lower installation costs than furnaces.
How Many Square Feet Will 4,000 – 80,000 BTU Heat?
If you already bought a specific size space heater or furnace and want to know the square footage it can heat, here are the quick answers:
| Heating Capacity | Square Footage (Hot Climate) | Square Footage (Moderate Climate) | Square Footage (Cold Climate) |
|---|---|---|---|
| 4,000 BTU | 130 sq ft | 85 sq ft | 70 sq ft |
| 5,000 BTU | 160 sq ft | 110 sq ft | 90 sq ft |
| 6,000 BTU | 200 sq ft | 130 sq ft | 105 sq ft |
| 9,000 BTU | 300 sq ft | 200 sq ft | 160 sq ft |
| 10,000 BTU | 320 sq ft | 220 sq ft | 180 sq ft |
| 11,000 BTU | 350 sq ft | 240 sq ft | 200 sq ft |
| 12,000 BTU | 400 sq ft | 260 sq ft | 200 sq ft |
| 15,000 BTU | 500 sq ft | 320 sq ft | 270 sq ft |
| 16,000 BTU | 530 sq ft | 350 sq ft | 290 sq ft |
| 20,000 BTU | 600 sq ft | 430 sq ft | 360 sq ft |
| 30,000 BTU | 1,000 sq ft | 600 sq ft | 500 sq ft |
| 40,000 BTU | 1,320 sq ft | 880 sq ft | 700 sq ft |
| 60,000 BTU | 2,000 sq ft | 1,300 sq ft | 1,100 sq ft |
| 75,000 BTU | 2,500 sq ft | 1,600 sq ft | 1,300 sq ft |
| 80,000 BTU | 2,700 sq ft | 1,800 sq ft | 1,450 sq ft |
For example, a 30,000 BTU space heater will heat 1,000 square feet in Florida, which is in hot climate. You can only heat 600 sq ft if you are living in cold climate.
For most areas, 40,000 BTU will heat 800 square feet. But if you live in very south, it can heat more than 1,000 sq ft.
BTUs: Definition and Ratings
A BTU is a measurement of heat – specifically, the heat needed to raise the temperature of one pound of water 1 degree Fahrenheit. The full name is British thermal unit.
It is an exact measurement that can be applied to most heating equipment. The correct rating is BTU/hour, or BTU/h, meaning how much heat does the equipment create in one hour of constant operation.
Furnaces rarely run for an hour straight, but that’s how they are rated.
Did you Know? BTU ratings are also used for air conditioning. The rating for ACs isn’t, obviously, the amount of heat the equipment creates, but the heat that it removes from a room each hour.
And for heat pumps, it is the same as for air conditioners – the amount of heat moved from outside to inside during heating.
Our guide How Many BTU Air Conditioner Do I Need? explains how BTUs apply to air conditioners and, to some extent, heat pumps.
How Many BTU Do Furnaces Make? Standard Boilers?
It’s a wide range. The smallest gas furnaces start at about 30,000 BTU per hour, or BTU/h.
While BTU/h, how many BTUs of heat the unit can create in one hour, is the technical specification, most heating equipment such as propane, oil and gas furnaces are rated simply by BTUs or BTU.
The most common sizes are from about 70,000 to 120,000 BTU/h.
The largest gas furnaces create about 140,000 BTU/h.
Oil furnaces have a slightly different range from about 60,000 to 160,000 BTU/h.
What About Wood Stove/Boilers and Combi Boilers?
Both of these heating equipment types provide both hot water for heat and water used to heat water in your hot water tank. The second half of that sentence is a mouthful – wood-burning combi boilers heat water – but that hot water doesn’t flow directly into your hot water pipes. Instead, it circulates through a pipe in your hot water tank to provide you with what is called “domestic” hot water. This type of heating equipment is growing in popularity, especially where free or cheap wood is readily available. See our Wood Furnace/Boiler Reviews and Buying Guide for details.
Written by Rene Langer
Rene has worked 10 years in the HVAC field and now is the Senior Comfort Specialist for PICKHVAC. He holds an HVAC associate degree from Lone Star College and EPA & R-410A Certifications.
FAQs
How many BTU heat do I need per square foot? ›
Warmer climates along the southern part of the United States - considered Zone 1 or 2 - require 30-40 BTU per square foot. The middle part of the country - Zone 3 and 4 - require between 40-45 BTU per square foot, while the northern areas of Zone 5 need up to 60 BTUs per square foot.
How many BTUs do you need to heat 1200 square feet? ›A 1,200-square-foot home will require between 35,000 and 75,000 BTUs. A 1,500-square-foot home will require between 45,000 to 90,000 BTUs. A 1,800-square-foot home will require between 55,000 to 110,000 BTUs.
How do you work out how many BTUs are needed? ›How is your room's BTU requirement calculated? A room's BTU requirement is based upon the cubic volume of the space – the height, length and the width of the room multiplied by four (done for you by our calculator) – and what is above, below and besides the room.
How many BTU do I need to heat a 20x20 room? ›| Room/Area Size | Heating Capacity(BTU) | Examples |
|---|---|---|
| 300 sq ft | 12,000-16,000 BTU | Efficiency apartment. 12x24 garage |
| 400 sq ft | 18,000-22,000 BTU | 20x20 room or garage |
| 500 sq ft | 22,000-27,000 BTU | Studio/1-bedroom apartment, Tiny house |
| 600 sq ft | 27,000-33,000 BTU | 20x30 room, 24x24 garage |
In short, for a 2,500 sq ft home, you would require a 6.25-ton heat pump.
What size furnace Do I need to heat a 2000 square foot home? ›A mid-sized home of 2,000 square feet would need approximately 50,000 to 60,000 Btu to heat it properly. With a less efficient furnace operating at 80 percent efficiency this would require a 60,000- to 72,000-Btu furnace.
How many BTU do I need for 1700 square feet? ›BTUs are used to measure a furnace's heat output. The general rule of thumb is that you want 40-45 BTUs of heat per square foot of your home. So, if your home is 3,000 square feet, you'll want a furnace that produces between 120,000 BTUs and 135,000 BTUs.
How many square feet is 12000 BTUs good for? ›12,000 BTUs will cover 400 sq. ft. (3,200 cubic feet) 13,000 BTUs will cover 450 sq.
What size furnace Do you need to heat a 1200 square foot house? ›1,200 square foot home would take between 35,000 and 75,000 BTUs. 1,500-square-foot home would take between 45,000 and 90,000 BTUs. 1,800-square-foot home would take between 55,000 and 110,000 BTUs. 2,100-square-foot home would take between 65,000 and 125,000 BTUs.
How many square feet will a 100 000 BTU furnace heat? ›
Determining the Square Footage
In colder climates, you'll want a furnace that generates 40 to 45 BTUs per square foot. At this amount, you'll need 100,000-112,500 BTU furnace to heat a home of 2,500 square feet.
The calculation is a simple one: the area of surface (in square metres) multiplied by the U-value, multiplied by the difference in temperature between the inside and outside, gives the loss of heat in Watts (per hour).
How many BTUs do I need for central heat and air? ›A window air conditioner might be around 5,000 to 10,000 BTUs, while residential central air conditioners average between 20,000 to 50,000 BTUs.
How many BTU do I need to heat a 12x12 room? ›The first technique is to simply figure the square footage of the space you want to heat. In warmer climates, multiply this number by 10 - 15. In more moderate climates, multiply by 20 - 30. And in cold climates multiply the square foot number by 30 - 40.
How many BTU do I need for 14x20 room? ›| Cooling Capacity (BTU): | Room Size: | Examples: |
|---|---|---|
| 6,000 BTU | 150 - 250 sq. ft. | 12x20 room |
| 7,000 BTU | 250 - 300 sq. ft. | 16x16 room, 12x24 room |
| 8,000 BTU | 300 - 350 sq. ft. | 18x18 room, studio apartment |
| 9,000 BTU | 350 - 400 sq. ft. | 18x20 room, studio apartment |
| Room Type | Room Size | Recommended BTU |
|---|---|---|
| 12 x 12 room | 144 sq ft | 5,000 BTU |
| 12 x 24 room | 576 sq ft | 12,000 BTU |
| 13 x 13 room | 169 sq ft | 6,000 BTU |
| 14 x 16 room | 224 sq ft | 6,000 BTU |
To effectively calculate what the BTU output for any room is, you have to start by getting a tape measure and measuring the height of the room, the width of the room, the length of the room and then finally the size of the window area (that's the length by width of a window in m²).
How many square feet will a 3 ton unit heat? ›If you Google “heat pump calculator,” you'll probably find a rule of thumb like this: “You need 30 BTUs of heat for every square foot of living space you want to heat or cool.”
How many square feet will a 3 ton unit heat and cool? ›3-ton is equal to 36,000 BTU. If you apply the 20 BTU per sq ft rule of thumb, you can see that a 3-ton air conditioner cools about 1,800 square feet spaces.
Is it better to undersize or oversize a furnace? ›
Even a slightly undersized furnace will accomplish the job the majority of the time. Taking things down a few sizes will more than likely solve some of your common heating problems like too high of a utility bill while half of your house is blazing and the other half is an icebox.
How many square feet will a 70 000 BTU furnace heat? ›| Furnace Capacity | Square Footage(Hot Climate) | Square Footage(Cold Climate) |
|---|---|---|
| 70,000 BTU | 2,320 sq ft | 1,270 sq ft |
| 80,000 BTU | 2,650 sq ft | 1,450 sq ft |
| 90,000 BTU | 3,000 sq ft | 1,630 sq ft |
| 100,000 BTU | 3,320 sq ft | 1,810 sq ft |
A furnace that's too big for your home can cause temperature inconsistencies. Even large furnaces may struggle with keeping the desired temperature in your home. You will notice that some rooms aren't as warmer as the other rooms.
How many square feet will a 18000 BTU heat and cool? ›Enjoy your home all seasons through with the LG 18,000 BTU Heat/Cool Window Air Conditioner - 1,000 sq. ft providing reliable heating and cooling. This air conditioner is able to treat a space from 550 to 1,000 square feet with 18,000 BTUs of cooling and 12,000 BTUs of heating power.
How many BTUs do I need for a 1400 square foot house? ›| House Square Footage | BTUs Needed |
|---|---|
| 700 – 1,000 | 18,000 |
| 1,000 – 1,200 | 21,000 |
| 1,200 – 1,400 | 23,000 |
| 1,400 – 1,500 | 24,000 |
700 – 1,000 sq. feet: 18,000 BTUs. 1,000 – 1,200 sq. feet: 21,000 BTUs.
How many square feet will a 60 000 BTU furnace heat? ›| Semi-detached House square footage * | Furnace Output [BTU/hr] | |
|---|---|---|
| 1800 to 2200 sq ft | 55,000 BTU/hr | 60,000 BTU/hr |
| 2200 to 3000 sq ft | 60,000 BTU/hr | 70,000 BTU/hr |
| *The above square footages do not include the area of the basement. | ||
For a space of 800 to 900 square feet, such as a small home or two-bedroom townhouse, the recommendation is between 30,000 and 45,000 BTUs. An average 2,000-square foot home will need between 80,000 and 115,000 BTUs to heat efficiently. Need a new furnace?
What size furnace do I need for a 3 ton AC unit? ›home, the air conditioner would need to be 37,500 ÷ 12,000, which comes out to about 3 tons. For the furnace, an 80% efficiency unit would need a BTU output of about 37,500 × 0.8, which is about 47,000 BTU.
What happens if BTU is too high? ›If your air conditioner has a bigger BTU rating than the room size needs, it will cycle off too quickly, waste energy, and will not adequately dehumidify the space. So a higher BTU than needed is definitely not recommended.
How many square feet does 12000 BTU heat and cool? ›
Answer: Using the EPA's 20 BTU per sq ft rule of thumb, the room size of 12,000 BTU air conditioners is 600 sq ft.
How much space will a 12000 BTU heat pump heat? ›General rules for a rough calculation
For a heat pump or wall-mounted air conditioner, it's about 1,000 BTU per 100 square feet. So for a 1,000 to 1,200 square foot area, your heat pump would be about 12,000 BTU. For the same area, if space is limited, the power can be reduced to 9,000 BTU.
Generally in a Californian climate you will need 25-30 BTU per square foot. BTU is a measurement of a furnace's heat output. 1500 sq feet by 25 BTU gives us a 37,500 BTU furnace.
What size furnace do I need for 1300 sq ft? ›| House Size (Sq Ft): | Furnace Size (in BTUs): |
|---|---|
| 1000 sq ft home | 45,000 BTU furnace |
| 1100 sq ft home | 49,500 BTU furnace |
| 1200 sq ft home | 54,000 BTU furnace |
| 1300 sq ft home | 58,500 BTU furnace |
So, a 1500 sq feet with 25 BTU energy requirements needs a 37,500 BTU furnace. If you live in colder areas of California, you can prefer calculating with 30 BTUs. That gives us an overall furnace size of 45,000 BTU. However, the same calculation won't apply to colder regions like Tecumseh.
What size central air and heat do I need? ›One ton is equal to 12,000 BTUs. The smallest standard size is 1.5 tons, which is 18,000 BTUs and the largest is 5.0 tons, which is 60,000 BTUs. To calculate for yourself how big of a central air conditioning unit you need, multiply your home's total square footage by 20. Divide that total by 12,000.
Is it better to be over or under BTU? ›More is not better. A unit with too many BTU's, will cool the room fast, but leave the room humid. Too few BTU's will never cool the room down and the unit will run incessantly. To be sure you're making the right decision, call us to get answers about air conditioner sizes and efficiency.
Is 12000 BTU too much for a bedroom? ›In our experience, a 12,000 BTU portable can work well in a bedroom up to about 200 square feet, and a 14,000 BTU unit will make some difference up to 400 square feet if you can tolerate the noise.
How many BTU do I need for a 12x10 room? ›Example 1: You want to cool just one room that is 10' long and 12' wide. By looking at our chart you would need an air conditioner with 5,000 BTU's to cool this room of 120 sq. ft.
Is 8000 BTU enough for a bedroom? ›Is An 8,000 BTU Unit Appropriate For Your Needs? An 8,000 BTU window AC or portable air conditioner is capable of cooling most standard bedrooms and offices. If you want to cool a larger space or multiple rooms, an 8,000 BTU air conditioner does not have enough power.
How many square feet will a 80000 BTU furnace heat? ›
| Detached House square footage * | Furnace Output [BTU/hr] | |
|---|---|---|
| 2500 to 3500 sq ft | up to 65,000 BTU/hr | up to 80,000 BTU/hr |
| 3500 to 4500 sq ft | up to 80,000 BTU/hr | up to 100,000 BTU/hr |
| *The above square footages do not include the area of the basement | ||
The higher the number of BTU's the larger the area a machine can efficienctly heat or cool. For example, a 9,000 BTU heat pump is suited for 250 to 450 square feet.
How many square feet does a 100000 BTU furnace cover? ›Determining the Square Footage
In colder climates, you'll want a furnace that generates 40 to 45 BTUs per square foot. At this amount, you'll need 100,000-112,500 BTU furnace to heat a home of 2,500 square feet.
To determine the number of BTUs per square foot that you need to heat a room, simply multiply the square footage by 20 BTUs per square foot. For example, if a room has 1,000 square feet, you would require 20,000 BTUs to heat it.
How many BTU do I need to heat and cool 600 square feet? ›If you Google “heat pump calculator,” you'll probably find a rule of thumb like this: “You need 30 BTUs of heat for every square foot of living space you want to heat or cool.” If you have a 2,000-square-foot home, this rule of thumb suggests you need a 60,000 BTU heat pump.
How many square feet will a 24000 BTU mini split heat and cool? ›| Mini Split Cooling Capacity | Room Size |
|---|---|
| 12,000 BTU | 550 - 650 sq ft |
| 15,000 BTU | 680 - 835 sq ft |
| 18,000 BTU | 820 - 1,000 sq ft |
| 24,000 BTU | 1,100 - 1,350 sq ft |
400 – 450 sq. feet: 10,000 BTUs. 450 – 550 sq. feet: 12,000 BTUs.
What size heat pump do I need for a 3000 square foot house? ›2,000 square feet: 4 tons. 2,500 square feet: 5 tons. 3,000 square feet: 6 tons.
How many square feet is 8000 BTU good for? ›
At 8,000 BTU, it has the cooling capacity for up to about 350 square feet.