Convert Therm to British Thermal Unit (thm → BTU)

Converting therms to BTU 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 therms

   Start with the number of therms (thm) you want to convert.
2. 2
   Multiply by 100,000

   The conversion factor from thm to BTU is 100,000. Multiply your value by this number.
3. 3
   Read the result in BTU

   The result is your value in BTU (BTU).

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

• ✓1 therm = 100,000 BTU = 105.5 MJ = 29.3 kWh.
• ✓UK bills often quote both therms and kWh.
• ✓In metric-dominant EU, gas is billed in kWh or m³.

• ✗Comparing therms and kWh without conversion on a mixed-unit bill.
• ✗Assuming therms are used globally — only US and UK.
• ✗Using BTU when bill shows therms — factor of 100,000.

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

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