Ah to kWh Calculator
Convert battery capacity from amp-hours (Ah) to kilowatt-hours (kWh) with the standard formula kWh = Ah × V ÷ 1000. Works both ways (kWh → Ah too), supports mAh, common battery voltage presets, series/parallel battery banks, and estimates how long your battery will run a device.
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How long will the converted capacity power a device?
Tip: lead-acid batteries should only be discharged to ~50%; lithium typically allows 80–100%.
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Frequently asked questions
What is the formula to convert Ah to kWh?
kWh = Ah × V ÷ 1000. Multiply the amp-hour rating by the battery voltage in volts, then divide by 1000. Example: 100 Ah × 12 V ÷ 1000 = 1.2 kWh.
How do I convert 20,000 mAh to kWh?
First convert milliamp-hours to amp-hours: 20,000 mAh = 20 Ah. Then apply the formula with the cell voltage: 20 Ah × 3.7 V ÷ 1000 = 0.074 kWh, which is 74 Wh.
Why do I need the voltage to convert Ah to kWh?
Amp-hours measure electric charge, while kilowatt-hours measure energy. Voltage is what links charge to energy, so the same 100 Ah rating is 1.2 kWh at 12 V but 4.8 kWh at 48 V — without voltage the conversion is impossible.
What voltage should I enter for a 12 V car battery?
Use the nominal 12 V for capacity comparisons. A rested lead-acid battery reads about 12.6–12.8 V, and charging systems run near 14.4 V, but the industry standard for Ah-to-kWh math is the nominal 12 V.
Do batteries in series or parallel give more kWh?
The same total. In series, voltage adds and amp-hours stay the same (two 100 Ah 12 V batteries give 24 V at 100 Ah). In parallel, amp-hours add and voltage stays (12 V at 200 Ah). Both give 2.4 kWh.
How do I convert kWh back to Ah?
Ah = kWh × 1000 ÷ V. Example: 1.2 kWh ÷ 12 V × 1000 = 100 Ah.
How long will my battery power a device?
Hours = kWh × usable fraction × 1000 ÷ load watts. Example: a 1.2 kWh battery running a 60 W load lasts 1.2 × 1000 ÷ 60 = 20 hours at 100% usable capacity.
What is depth of discharge (DoD)?
The share of a battery's rated capacity you can safely use. Lead-acid batteries should only be discharged to about 50% DoD, while lithium batteries typically allow 80–100%. Usable kWh = rated kWh × DoD fraction.
Why does my 20,000 mAh power bank only charge my phone twice?
The 20,000 mAh rating is at the internal cell voltage of 3.7 V, which is only 74 Wh. USB output at 5 V gives about 14,800 mAh in theory, and boost-converter losses take more — real delivered energy is closer to 60 Wh.
Is Ah or kWh better for comparing batteries?
kWh. Amp-hour ratings at different voltages are not comparable — a 100 Ah 12 V battery (1.2 kWh) holds over three times the energy of a 100 Ah 3.7 V pack (0.37 kWh). Kilowatt-hours measure actual energy.
Does this tool replace a watt-hour energy calculator?
No. This tool converts battery Ah ratings using voltage. For energy-bill math (energy = power × time), use the electrical-unit-converter (mode 3); for grid-scale megawatt conversions use the megawatt-to-kwh-calculator.
Can I use this for EV or solar battery banks?
Yes. Enter the pack voltage — for example 400 V for an EV or 24/48 V for solar — or combine multiple batteries with the series/parallel bank mode. A 150 Ah 400 V EV module holds 150 × 400 ÷ 1000 = 60 kWh.
Free tool by NRTechStudio