BTU to Square Footage Calculator: How Many BTUs Do I Need?
Keep cool while you calculate
Estimate 20 to 25 BTUs per square foot for cooling.
Estimate 30 to 35 BTUs per square foot for heating.
Better insulation in your home lowers the BTUs you need.
Extreme climates require higher BTUs.
Double-check your BTUs with an HVAC pro to ensure the highest energy efficiency.
The right BTUs ensure your HVAC system is primed for energy efficiency and long-term cost savings. Whether you’re looking for a furnace or AC, use our BTU to square footage chart to determine the right BTUs for your space.
How Many BTUs Are Needed For an Air Conditioner or Furnace
Using square footage, refer to the table below to estimate how many BTUs you need. The chart is based on a ceiling height of nine feet or less.
If your home is well-insulated, you’ll need fewer BTUs to heat and cool the space. If you live in a more extreme climate (hot or cold), you’ll need higher BTUs.
| Square Footage | BTUs Needed for Heating (30 BTUs per Square Foot) (Poor Insulation / Extreme Climate) | BTUs Needed for Heating (35 BTUs per Square Foot) (Good Insulation / Moderate Climate) | BTUs Needed for Cooling (20 BTUs per Square Foot) (Poor Insulation / Extreme Climate) | BTUs Needed for Cooling (25 BTUs per Square Foot) (Good Insulation / Moderate Climate) |
|---|---|---|---|---|
| 100 to 250 | 3,000 to 7,500 | 3,500 to 8,750 | 2,000 to 5,000 | 2,500 to 6,250 |
| 251 to 500 | 7,530 to 15,000 | 8,785 to 17,500 | 5,020 to 10,000 | 6,275 to 12,500 |
| 501 to 700 | 15,030 to 21,000 | 17,535 to 24,500 | 10,020 to 14,000 | 12,525 to 17,500 |
| 701 to 1,000 | 21,030 to 30,000 | 17,535 to 35,000 | 14,020 to 20,000 | 17,525 to 25,000 |
| 1,001 to 1,500 | 30,030 to 45,000 | 35,035 to 52,500 | 20,020 to 30,000 | 25,025 to 37,500 |
| 1,501 to 2,000 | 45,030 to 60,000 | 52,535 to 70,000 | 30,020 to 40,000 | 37,525 to 50,000 |
| 2,001 to 2,500 | 60,030 to 75,000 | 70,035 to 87,500 | 40,020 to 50,000 | 50,025 to 62,500 |
| 2,501 to 3,000 | 75,030 to 90,000 | 87,535 to 105,000 | 50,020 to 60,000 | 62,525 to 75,000 |
| 3,001+ | 90,030+ | 105,035+ | 60,020+ | 75,025 |
Calculating BTU to Square Footage
Using your square footage, apply the following formula to determine how much BTU you need:
BTUs needed for heating = square footage x 20 to 25 BTUs (adjust for insulation and climate)
BTUs needed for cooling = square footage x 25 to 30 BTUs (adjust for insulation and climate)
Depending on your insulation and climate, you need 20 to 25 BTUs per square foot for cooling. Aim for the lower end if you have good insulation or live in a moderate climate. Choose the higher end if you have poor insulation or live in an extreme climate.
Depending on your insulation and climate, you need 30 to 35 BTUs per square foot for heating. Aim for the lower end if you have good insulation or live in a moderate climate. Choose the higher end if you have poor insulation or live in an extreme climate.
How to Measure Square Footage for BTU
You’ll want to measure the square footage of your room or home and then adjust the BTUs based on your climate and insulation.
How to Measure Square Footage
Use the blueprint of your house or the most recent real estate listing to determine the square footage of your home. You can also measure the size of a room by measuring the length and the width with a tape measure. Multiply the width by the length to get your square footage.
How to Adjust for Climate, Insulation, and Other Factors
The BTUs you need depend significantly on the level of insulation in your home and the climate you live in. If you have moderate or excellent insulation, aim on the lower end of BTUs, as you won’t need as much energy to heat and cool the space. Your climate also impacts the BTUs required. Aim for more BTUs if you live in an extreme environment, such as freezing temperatures or ultra-hot summers.
Who to Hire to Install an Air Conditioner or Furnace
A local HVAC pro should always install a heating and cooling system to ensure safety, efficiency, and long-term cost savings. HVAC professionals have the knowledge and tools to ensure the job is done right. On average, a new HVAC system costs $7,500, but prices vary between $5,000 and $12,50, depending on your climate and square footage.
Frequently Asked Questions
You need 20 to 25 BTUs per square foot for cooling and 30 to 35 BTUs per square foot for heating. If your home has poor insulation, aim for the higher end. If you live in an extreme climate, aim for the higher end too. Choose the lower end if you have a well-insulated home or live in a moderate climate.
You can determine your BTUs by multiplying your square footage by 20 to 25 for cooling and 30 to 35 for heating. You need fewer BTUs if you have sound insulation or live in a moderate climate. You need more BTUs if you have poor insulation or live in an extreme environment. Talk with an HVAC pro to verify your BTUs before installing a heating or cooling system.
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