BTU Calculator

Determine the perfect air conditioner or heater size for your space

12 ft
10 ft

Air Conditioning Requirements

Room Area

0
square feet

Room Volume

0
cubic feet

BTU Required

0
BTU/hour

Recommended AC Unit Size

Heating Requirements

Room Area

0
square feet

Room Volume

0
cubic feet

BTU Required

0
BTU/hour

Recommended Heater Size

Common BTU Conversions

Unit Equivalent To Common Uses
1 BTU/hour 0.293071 Watts Basic measurement of heating/cooling
1 Ton of Refrigeration 12,000 BTU/hour Central air conditioners
1 Watt 3.41214 BTU/hour Electrical heating devices
1 Kilowatt 3,412.14 BTU/hour Larger HVAC systems
1 Horsepower 2,544.43 BTU/hour Industrial applications

Understanding BTU Requirements

What is BTU?

BTU (British Thermal Unit) is a measurement of heat energy. One BTU is the amount of energy needed to raise the temperature of one pound of water by one degree Fahrenheit.

In HVAC terms:

  • Cooling: BTUs measure how much heat an air conditioner can remove per hour
  • Heating: BTUs measure how much heat a heater can produce per hour

Choosing the right BTU capacity is crucial for efficiency and comfort.

Why Proper Sizing Matters

Too small unit:

  • Struggles to heat/cool the space
  • Runs constantly, increasing energy bills
  • Wears out faster from overuse

Too large unit:

  • Short cycling (frequent on/off)
  • Poor humidity control (especially for AC)
  • Higher upfront cost
  • Energy inefficiency

Factors Affecting Cooling BTU Requirements

Sun Exposure

Sunny rooms need 10% more cooling power. South-facing windows add significant heat.

Occupancy

Each person adds about 400 BTU to the cooling load (body heat).

Appliances

Kitchens need extra cooling (about 4,000 BTU more) due to heat from cooking.

Factors Affecting Heating BTU Requirements

Insulation

Poor insulation can increase heating needs by 20-30%.

Windows

Single-pane windows lose 2-3 times more heat than double-pane.

Climate

Colder climates may need 30-40% more heating capacity.

Standard BTU Recommendations

Room Size (sq ft) Cooling BTUs Heating BTUs AC Unit Size
100-150 5,000 4,000-5,000 Small window unit
150-250 6,000 5,000-7,000 Medium window unit
250-300 7,000 7,000-9,000 Large window unit
300-350 8,000 9,000-11,000 Small portable AC
350-400 9,000 11,000-13,000 Large portable AC
400-450 10,000 13,000-15,000 Mini-split system
700-1,000 18,000 20,000-25,000 1.5 ton central AC
1,000-1,200 21,000 25,000-30,000 2 ton central AC