Watt-Hours to Milliamp-Hours Converter (Wh to mAh & Battery Sizing

Watt-Hours (Wh) to Milliamp-Hours (mAh) & Cell Voltage Scaling

Converting true stored energy in Watt-Hours to electric charge capacity in Milliamp-Hours requires knowing the nominal cell voltage:

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• Universal Wh to mAh Conversion Formula**:

Capacity (mAh) = E_Wh × 1,000V_nominal

Capacity (Ah) = E_WhV_nominal

Q_Coulombs = Capacity (Ah) × 3,600 s = E_Wh × 3,600V_nominal

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• The Impact of Nominal Voltage on mAh Ratings**:

• At higher voltages, less charge capacity (mAh) is required to deliver the same energy:

• 100 Wh @ 3.7V (1S Li-Ion): (100 × 1000) / 3.7 = 27,027 mAh

• 100 Wh @ 7.4V (2S Li-Ion): (100 × 1000) / 7.4 = 13,514 mAh

• 100 Wh @ 11.4V (3S Laptop): (100 × 1000) / 11.4 = 8,772 mAh

• 100 Wh @ 12.0V (Lead-Acid): (100 × 1000) / 12.0 = 8,333 mAh

• 100 Wh @ 36.0V (10S E-Bike): (100 × 1000) / 36.0 = 2,778 mAh

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• Standard Device Energy Benchmarks**:

• 18.5 Wh @ 3.7V: 5,000 mAh (Modern flagship smartphone)

• 60.0 Wh @ 11.4V: 5,263 mAh (Ultrabook laptop battery)

• 100.0 Wh @ 3.7V: 27,027 mAh (Maximum TSA airplane power bank)

• 500.0 Wh @ 36.0V: 13,889 mAh (City commuter electric bicycle)

• 720.0 Wh @ 12.0V: 60,000 mAh (60 Ah) (Automotive starter battery)

How to Use This Calculator

Enter your Stored Battery Energy (Watt-Hours / Wh) (e.g. 100 in Wh), Nominal Battery Voltage (Volts / V) (e.g. 3.7 for Li-ion, 11.4 for Laptop, 12.0 for Car in V), Battery Cell Chemistry Standard — choose from Single-Cell Lithium-Ion / LiPo (3.7V Nominal), 3-Cell Laptop Li-Ion Pack (11.4V Nominal), Lead-Acid Automotive SLI (12.0V Nominal), and Battery Device Benchmark — choose from Custom Wh & Voltage, 18.5 Wh Smartphone Battery (3.7V) → 5,000.0 mAh, 60.0 Wh Laptop Internal Pack (11.4V) → 5,263.16 mAh. Results update instantly as you type — adjust any value to compare scenarios.

The Formula

Calculate Capacity in mAh: mAh = (Wh * 1000) / V

Worked Example

A consumer buying a laptop replacement battery labeled '60 Wh, 11.4V' converts to milliamp-hours: / 11.4 = 5,263 mAh, confirming it matches the original factory battery specification.

Understanding Your Result

Unit conversion precision: round to the same number of significant figures as your original measurement. Converting 6 feet to meters gives 1.8288 m — but if your measurement was approximate (±1 inch), expressing more than 2 decimal places is false precision. For international trade and technical specifications, SI units (meters, kilograms, liters) are the standard. US customary units (feet, pounds, gallons) differ from Imperial UK units: 1 US gallon = 3.785 L vs. 1 UK gallon = 4.546 L.