MihsabaHow to use
Watt-hours describe nominal battery energy, while amp-hours describe charge capacity, so voltage is required to convert between them. Enter the battery’s energy in Wh and its nominal voltage in V to obtain Ah and mAh. A 120 Wh battery corresponds to 10 Ah at 12 V but 5 Ah at 24 V. Multiply kWh by 1,000 before entering it. Use the pack’s nominal voltage rather than a charging-port voltage that may differ. Equal Ah ratings at different voltages do not represent equal amounts of energy.
- Enter Battery energy (Wh).
- Enter Nominal voltage (V).
- Calculate and check the result and its unit.
How it is calculated
Example
A nominal 1,280 Wh battery at 12.8 V gives 100 Ah, or 100,000 mAh. This is nominal capacity, not a promise that all stored energy is usable.
Important notes
Voltage changes during discharge; this relation uses nominal voltage to estimate a label capacity. It does not account for inverter efficiency, depth of discharge, aging or load current. Do not reinterpret a battery’s Ah rating by substituting a USB output voltage for its cell voltage. This tool does not determine shipping or travel eligibility or assess battery safety.
Worked examples and interpreting results
A nominal 1,280 Wh battery at 12.8 V gives 100 Ah, or 100,000 mAh. This is nominal capacity, not a promise that all stored energy is usable.
| Case | Calculation | Result |
|---|---|---|
| Amp-hours | 1280 ÷ 12.8 | 100 Ah |
| Milliamp-hours | 100 × 1000 | 100,000 mAh |
| Same energy at 24 V | 1280 ÷ 24 | 53.333333 Ah |
How to check the result
Voltage changes during discharge; this relation uses nominal voltage to estimate a label capacity. It does not account for inverter efficiency, depth of discharge, aging or load current. Do not reinterpret a battery’s Ah rating by substituting a USB output voltage for its cell voltage. This tool does not determine shipping or travel eligibility or assess battery safety.
Frequently asked questions
Can Wh be converted to Ah without voltage?
No. Divide Wh by nominal volts; the resulting charge capacity changes with voltage even when energy stays the same.
How do I convert Ah to Wh?
Multiply Ah by nominal voltage. A 100 Ah battery at 12.8 V is nominally 1,280 Wh.
How do I convert mAh to Wh?
Divide mAh by 1,000 and multiply by nominal voltage. For example, 10,000 mAh at 3.7 V is 37 Wh, not 50 Wh just because a USB output is 5 V.
Do amp-hours tell me device runtime?
Not by themselves. You also need device consumption, voltage, usable energy and conversion efficiency. Compare Wh first when battery voltages differ.