Convert British Thermal Unit to Therm (BTU → thm)

Converting BTU to therms is straightforward: multiply by the conversion factor. Follow these three steps to do it by hand or in your head.

1. 1
   Take your value in BTU

   Start with the number of BTU (BTU) you want to convert.
2. 2
   Multiply by 0.00001

   The conversion factor from BTU to thm is 0.00001. Multiply your value by this number.
3. 3
   Read the result in therms

   The result is your value in therms (thm).

Multiply the value in BTU by 0.00001. For the reverse direction, multiply by 100,000.

• ✓1 BTU = 1055.06 J = 0.293 Wh.
• ✓BTU/h (power) and BTU (energy) are different — don't confuse.
• ✓Tons of refrigeration: 12,000 BTU/h = 1 ton AC.

• ✗Confusing BTU and BTU/h — energy vs power.
• ✗Using kcal when BTU is requested in HVAC specs.
• ✗Treating all BTUs as exact — definitions vary (IT, thermochemical, etc.).

What is the British Thermal Unit?

The British thermal unit (BTU) equals approximately 1,055.06 joules and is the standard unit in American HVAC, gas appliances, and air-conditioner ratings. Originally defined as the heat needed to raise 1 pound of water by 1°F, the BTU is the imperial counterpart to the calorie. American gas utilities measure delivered heat in BTUs or therms (1 therm = 100,000 BTU), and air conditioners are rated by their cooling capacity in BTU per hour (a typical window AC is 5,000–12,000 BTU/h, central AC for a medium home is 24,000–60,000 BTU/h). Furnaces are similarly rated. The BTU relates to the joule (1 BTU ≈ 1,055 J), the calorie (1 BTU ≈ 252 cal), the watt-hour (1 BTU ≈ 0.293 Wh), and the therm (100,000 BTU = 1 therm). Outside the United States, the BTU is rare; metric countries use kilojoules or kilowatt-hours for the same applications.

• US air-conditioner sizing
• US heating-system capacity
• Natural gas billing in some US regions

What is the Therm?

The therm equals exactly 100,000 BTU (or about 105.5 megajoules) and is the standard unit for natural-gas billing in the United States and the United Kingdom. Gas utilities deliver therms (or 'CCF' — hundred cubic feet, approximately 1 therm of natural gas). A typical US home uses 50–100 therms per month for heating in winter. The therm is also used in industrial process heating and commercial gas pricing. UK natural gas was historically sold in therms before metric conversion, and the unit persists in legacy contracts. The therm relates to the BTU (100,000 BTU = 1 therm), the megajoule (1 therm ≈ 105.5 MJ), the kilowatt-hour (1 therm ≈ 29.3 kWh), and the cubic foot of natural gas (about 100 ft³ ≈ 1 therm at standard heating value). Most metric countries bill natural gas in cubic meters or kilowatt-hours instead.

• US residential gas bills
• UK commercial gas billing
• Industrial natural-gas contracts