Convert Therm to Calorie (thm → cal)

Converting therms to calories 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 25,216,440

   The conversion factor from thm to cal is 25,216,440. Multiply your value by this number.
3. 3
   Read the result in calories

   The result is your value in calories (cal).

Multiply the value in therms by 25,216,440. For the reverse direction, multiply by 3.966 × 10^-8.

• ✓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 Calorie?

The calorie equals exactly 4.184 joules (the 'thermochemical calorie') and is the historical unit for heat in chemistry and physics. It was originally defined as the heat needed to raise 1 gram of water by 1°C (a definition that varied slightly with starting temperature, hence multiple 'calories' — 4.184 J was set as the exact thermochemical convention). The calorie is widely used in older physics and chemistry literature for reaction energies, specific heat capacities, and thermodynamic calculations. Note: this 'small calorie' (lowercase c) is 1/1000 of the food Calorie (capital C) used in nutrition. The chemistry calorie relates to the joule (4.184 J = 1 cal), the kilocalorie (1,000 cal = 1 kcal = 1 food Calorie), and the BTU (1 BTU ≈ 252 cal). Modern SI usage in scientific publications has largely replaced the calorie with the joule, but it persists in medical and chemistry contexts.

• Thermodynamics and older physics texts
• Chemistry energy calculations
• Some engineering heat-transfer contexts