Amp Hour Calculator

What the amp hour calculator shows

Batteries are rated two ways: amp hours (Ah), which describe charge, and watt hours (Wh), which describe energy. The amp hour calculator links them through the battery voltage. That makes it an ah converter for comparing batteries of different voltages, sizing a power station, or checking a phone or laptop battery in mAh.

Ampere hour to watt hour formula

The ampere hour to watt hour formula multiplies charge by voltage, and the reverse divides:

Voltage is the link, so the same amp hours hold four times the energy at 48 V as at 12 V. Any amp hour to watt hour conversion needs the voltage.

Watt hour to ampere hour example

A 100 Ah battery at 12 V. The amp hour calculator gives:

Going the other way, the watt hour to ampere hour conversion for a 1,200 Wh pack at 12 V is 1,200 ÷ 12 = 100 Ah. A 3,000 mAh phone cell at 3.7 V holds 3 × 3.7 = 11.1 Wh.

How to use the Ah to Wh conversion

For an ah to wh conversion, enter the capacity in amp hours and the nominal voltage; the amp hour calculator returns watt hours, kilowatt hours, and milliamp hours. For the reverse, convert watt hours to amp hours by typing the watt hours in the optional box with the same voltage. Use the nominal voltage printed on the battery, such as 3.7 V for a lithium cell or 12 V for a car battery.

Reading the ah converter result

Watt hours are the fairest way to compare batteries, because they include voltage. Amp hours only compare batteries of the same voltage. Usable energy is lower than the rated figure: lead-acid batteries should not be drained below about half, while lithium batteries can use 80 to 90 percent. Inverter losses take another 5 to 15 percent.

When to use the wh to ah converter

• Comparing a 12 V and a 24 V battery with the wh to ah converter
• Sizing a solar or camping battery bank
• Checking airline limits, which are set in watt hours
• Doing a mah wh conversion for phones and power banks

Common amp hour calculator mistakes

• Comparing Ah across voltages. Convert to Wh first.
• Using full rated capacity. Allow for depth-of-discharge limits.
• Converting Ah to amps without time. Current needs a duration.

Tips for accurate results

• Use the nominal voltage, not the full-charge voltage.
• Allow 10 to 20 percent for inverter and wiring losses.
• Check airline limits in watt hours before flying.

Related to the amp hour calculator

Capacity is only half of the story. The battery life calculator turns capacity and load into runtime, and the watts to amps calculator finds the current a device draws from its power.

Ampere hour to ampere and Ah to amps calculator

An amp hour is a current flowing for a time, so converting ampere hour to ampere needs a duration: amps = Ah ÷ hours. A 100 Ah battery rated over 20 hours can supply about 5 A for that time. An ah to amps calculator works this way, and an amp to ah calculator reverses it: amps times hours gives amp hours. Higher discharge rates usually reduce the real capacity. Once you know the energy in kWh, the energy cost calculator shows what it would cost to charge from the grid.

Ah to kWh calculator for battery banks

For larger systems, an ah to kwh calculator is the cleaner way to compare: divide watt hours by 1,000. To convert ah to kwh, multiply amp hours by volts and divide by 1,000; to convert kwh to amp hours, multiply kWh by 1,000 and divide by volts. Any ah kwh calculator or kwh to ah calculator uses exactly this pair of steps, and the same idea covers a mah to ah conversion: divide mAh by 1,000. Four 100 Ah 12 V batteries hold 4.8 kWh whether they are wired as a 12 V bank of 400 Ah or a 48 V bank of 100 Ah, because the energy stays the same.

Ah to watt hour conversion chart

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