Convert Ah or mAh to kWh and Wh, or reverse-solve battery capacity, with voltage, depth of discharge, efficiency, usable energy, and runtime.

Enter capacity and nominal voltage.

Nominal voltage gives an estimate. Defaults assume 100% usable capacity and 100% efficiency; adjust optional settings for losses.

Usable capacity, losses and runtime

Blank uses 100%; an ideal assumption, not a battery recommendation.

Blank uses 100% (no conversion loss).

Blank omits runtime. Zero load has no finite runtime estimate.

Common Mistakes Quick tips
  • Leaving voltage blank or using the wrong unit; convert mV to V when needed.
  • Select the value to solve for. Only relevant input fields are enabled; use delivered energy after losses for reverse battery sizing.
  • Confusing amps (A) with amp-hours (Ah); Ah is capacity, not instantaneous current.
  • Mixing Wh and kWh or using pack voltage incorrectly; use nominal system voltage and remember 1 kWh = 1000 Wh.
When to Use This Calculator
  • Sizing batteries from energy needs (kWh) or estimating stored energy from capacity (Ah).
  • Comparing battery packs across different voltages (12 V, 24 V, 48 V, etc.).
  • Converting datasheet ratings for solar, RV, UPS, and backup power planning.
Input Definitions
  • Voltage — system/battery voltage in V or mV (1 V = 1000 mV).
  • Capacity — amp-hours (Ah) or milliamp-hours (mAh), where 1000 mAh = 1 Ah.
  • Energy — watt-hours (Wh) or kilowatt-hours (kWh), where 1 kWh = 1000 Wh.
  • Conversions — nominal Wh = Ah × V; nominal kWh = Wh ÷ 1000. Delivered Wh = nominal Wh × usable-depth fraction × efficiency. Reverse sizing uses delivered Wh ÷ depth fraction ÷ efficiency ÷ V.

Ah to kWh Formula

The formulas below describe nominal energy from charge capacity and constant or representative battery voltage. Delivered energy also multiplies nominal energy by usable depth-of-discharge and efficiency fractions; the calculator defaults both to 100%.

Wh = Ah × V kWh = (Ah × V) / (1000) Ah = (1000 × kWh) / (V)
  • 1 kWh = 1000 Wh and 1 Wh = 1 V × 1 Ah.
  • Metric prefixes: 1000 mAh = 1 Ah and 1000 mV = 1 V.

How do you convert Ah to kWh? Multiply capacity by voltage and divide by 1000: kWh = Ah × V ÷ 1000.

How do you convert kWh to Ah? For nominal energy, Ah = kWh × 1000 ÷ V. For required delivered energy, divide again by the usable-depth fraction and efficiency. For example, 0.864 kWh delivered at 12 V, 80% depth and 90% efficiency requires 100 Ah.

Ah to kWh Conversion Table

Ah to kWh (12 V)
Capacity (Ah) Energy (kWh)
10.012
20.024
50.060
100.120
120.144
200.240
250.300
300.360
400.480
500.600
600.720
750.900
800.960
901.080
1001.200
1201.440
1501.800
2002.400
2503.000
3003.600
* Formula: kWh = Ah × V ÷ 1000. Table shows nominal energy at V = 12; usable depth and efficiency are 100% for the matching delivered-energy values.

Example Problem

Convert 100 Ah at 12 V to kWh.

Use the formula: kWh = Ah × V ÷ 1000.

kWh = 100 × 12 ÷ 1000 = 1.2 kWh