Watt-Hour Calculator
Free online Watt-Hour Calculator that runs directly in your browser.
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Watt Hour & Battery Calculator
Precisely calculate energy consumption, device operating time or convert battery capacity (mAh ↔ Wh).
Calculate energy consumption based on the device power and operating time.
Check how long the device will operate with a given amount of energy.
Calculate the average power required to consume energy over a specific period of time.
Battery capacity conversion. Required voltage (Li-Ion standard is 3.7V).
Enter data
Complete the form on the left to see calculation results, costs and statistics.
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Related tools
Other tools you may find usefulWatt-hour (Wh) calculator – calculate the energy, power and operating time of the device
Calculate the amount of energy consumed or stored by an electrical device. The Watt-hour (Wh) calculator converts power, runtime and battery capacity, and allows you to convert energy units tokWh, J, MJ i Ah. Indispensable in photovoltaics, electronics and energy consumption calculations.
Run watt-hour calculator See formulas and examples
What is a watt-hour (Wh)
A watt-hour is a unit of energy representing the amount of work done by a device with a power of 1 watt for 1 hour. In practice, it is used to determine electricity consumption, battery capacity and the efficiency of energy systems.
Basic energy formula
E = P × t
where:
E – energy [Wh]
P – device power [W]
t – operating time [h]This means that a 100 W device operating for 5 hours will consume 500 Wh (0.5 kWh) of energy. The calculator performs this conversion automatically, also allowing you to take into account voltage and capacity in Ah.
Auxiliary formulas
E (Wh) = U [V] × I [A] × t [h]
E (Wh) = C [Ah] × U [V]
1 Wh = 3600 J
1 kWh = 1000 Wh = 3.6 MJHow to use the calculator
- Enter the power of the device in watts (W).
- Enter the run time in hours or minutes.
- ClickCalculate- the tool will give the result in Wh, kWh and J.
- If you know the voltage and capacity of the battery, the calculator will convert the energy from Ah to Wh.
Calculation examples
Home LED bulb
P = 10 W, t = 8 h → E = 80 Wh = 0.08 kWh.
This means that the light bulb will use 0.08 kWh of energy per day.
Laptop
P = 65 W, t = 4 h → E = 260 Wh = 0.26 kWh.
That's about 94,000 J of energy.
Solar panel
P = 200 W, t = 5 h → E = 1000 Wh = 1 kWh.
This is how much energy can be stored in a 12V 83Ah battery.
Battery
C = 100 Ah, U = 12 V → E = 1200 Wh = 1.2 kWh.
A perfect example of converting capacity into energy.
Energy unit conversions
| Unit | Equivalence |
|---|---|
| 1 Wh | 3600 J |
| 1 kWh | 3.6×10⁶ J |
| 1 J | 2.778×10⁻⁴ Wh |
| 1 Ah (12V) | 12 Wh |
| 1 Wh | 0.001 kWh |
Inverse formulas
P = E / t
t = E/P
C = E/U
U = E / CThe calculator allows you to find the missing quantity among: energy, power, time, voltage and capacity. Thanks to this, you can calculate how long the battery will power a given device or how much energy the equipment will consume in a specific time.
Frequently asked questions (FAQ)
How to convert Wh to kWh?
Divide the value in Wh by 1000. For example, 500 Wh = 0.5 kWh.
How to convert Wh to Ah?
Use the formula Ah = Wh / V. For a 12 V battery and an energy of 120 Wh you will get 10 Ah.
How to calculate battery energy?
Multiply the voltage by the capacity: E = U × Ah. Result in Wh or kWh.
Does the calculator work for DC and AC current?
Yes. For alternating current, you can enter the effective value of voltage and power.
Uses of the
- Calculator Estimate the energy consumption of home appliances.
- Design of photovoltaic and battery systems.
- Equipment energy efficiency analysis.
- Conversion of battery capacity into real operating time.
Summary:Watt-hour calculator allows you to calculate electricity based on power, time and voltage. Useful in photovoltaics, electronics and home electricity bill calculations. Allows conversion between Wh, kWh, Ah and J.