Convert Therm to Watt-Hour (thm → Wh)

Converting therms to watt-hours 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 29,307.107

   The conversion factor from thm to Wh is 29,307.107. Multiply your value by this number.
3. 3
   Read the result in watt-hours

   The result is your value in watt-hours (Wh).

Multiply the value in therms by 29,307.107. For the reverse direction, multiply by 0.00003412.

• ✓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 Watt-Hour?

The watt-hour equals exactly 3,600 joules and is the standard unit for small-battery capacity, household electrical energy, and renewable-energy storage. A smartphone battery stores roughly 12–15 Wh, a laptop battery 50–100 Wh, and an electric car battery 60,000–100,000 Wh (60–100 kWh). The watt-hour represents the energy delivered by a 1-watt device running for 1 hour. It is the natural unit for connecting power (watts) to time, which is why electric utilities bill in kilowatt-hours. The watt-hour relates to the joule (3,600 J = 1 Wh), the kilowatt-hour (1,000 Wh = 1 kWh), and the BTU (1 Wh ≈ 3.412 BTU). Battery capacity, solar panel output (Wh per day), and energy storage system specifications all rely on the watt-hour as the base small-energy unit.

• Laptop and phone battery capacity
• Portable power banks and UPS
• Home solar panel daily output