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What is a watt-hour?

The small-battery capacity unit — 1 W × 1 hour

Definition

The watt-hour equals 3600 joules — 1 W delivered for 1 hour. Used for phone, laptop and small-battery capacities. A typical smartphone battery is 10–20 Wh; a laptop is 50–100 Wh.

Common uses

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

🌍 Real-world scale

iPhone battery: 12 Wh. MacBook Pro: 70 Wh. Power bank: 20 Wh–100 Wh. Airplane carry-on limit: usually 100 Wh.

Convert from watt-hours

9 conversions
Watt-Hour to Joule1 Wh = 3,600 JWatt-Hour to Kilojoule1 Wh = 3.6 kJWatt-Hour to Megajoule1 Wh = 0.0036 MJWatt-Hour to Kilowatt-Hour1 Wh = 0.001 kWhWatt-Hour to Calorie1 Wh = 860.421 calWatt-Hour to Kilocalorie1 Wh = 0.8604 kcalWatt-Hour to British Thermal Unit1 Wh = 3.41214 BTUWatt-Hour to Electronvolt1 Wh = 2.2469e22 eVWatt-Hour to Therm1 Wh = 3.4121e-5 thm

Convert to watt-hours

9 conversions
Joule to Watt-Hour1 J = 0.0002778 WhKilojoule to Watt-Hour1 kJ = 0.2778 WhMegajoule to Watt-Hour1 MJ = 277.778 WhKilowatt-Hour to Watt-Hour1 kWh = 1,000 WhCalorie to Watt-Hour1 cal = 0.001162 WhKilocalorie to Watt-Hour1 kcal = 1.16222 WhBritish Thermal Unit to Watt-Hour1 BTU = 0.2931 WhElectronvolt to Watt-Hour1 eV = 4.4505e-23 WhTherm to Watt-Hour1 thm = 29,307.11 Wh

Tips

  • 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.

Common mistakes

  • 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.

FAQ about the watt-hour

What is a watt-hour?
The watt-hour equals 3600 joules — 1 W delivered for 1 hour. Used for phone, laptop and small-battery capacities. A typical smartphone battery is 10–20 Wh; a laptop is 50–100 Wh.
Where is the watt-hour used?
The watt-hour is commonly used for: Laptop and phone battery capacity; Portable power banks and UPS; Home solar panel daily output.
What is an example of a watt-hour in real life?
iPhone battery: 12 Wh. MacBook Pro: 70 Wh. Power bank: 20 Wh–100 Wh. Airplane carry-on limit: usually 100 Wh.
What category does the watt-hour belong to?
The watt-hour is a unit of energy, part of the 10-unit energy category on UnitConv.
How accurate are watt-hour conversions?
All conversion factors follow NIST and BIPM international standards to 8 significant figures — the highest practical accuracy.
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