Convert Watt-Hour to Therm (Wh → thm)

Converting watt-hours 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 watt-hours

   Start with the number of watt-hours (Wh) you want to convert.
2. 2
   Multiply by 0.00003412

   The conversion factor from Wh to thm is 0.00003412. 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 watt-hours by 0.00003412. For the reverse direction, multiply by 29,307.107.

• ✓1 Wh = 3600 J = 0.001 kWh.
• ✓Battery mAh × V = Wh. A 3000 mAh phone battery at 3.7 V = 11.1 Wh.
• ✓Airline limits lithium batteries to 100 Wh for carry-on.

• ✗Confusing mAh with Wh — need voltage to convert.
• ✗Using Wh when kWh is more appropriate for large batteries.
• ✗Forgetting the voltage in battery capacity calculations.

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

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