What is a 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.

Visual reference for how the therm relates to other energy units. Each row links to the full converter for that pair.

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

• ✓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.