Amp-Hour to Milliamp-Hour Converter (Ah to mAh & Battery Energy

Amp-Hours (Ah), Milliamp-Hours (mAh) & Stored Battery Energy (Wh)

Battery capacity measures the total amount of electric charge a cell can deliver over time:

• **

• Universal Ah to mAh Conversion Formulas**:

Capacity (mAh) = Capacity (Ah) × 1,000

Capacity (Ah) = Capacity (mAh)1,000

Q_Coulombs = Capacity (Ah) × 3,600 seconds

• **

• Stored Energy Formulas (Watt-Hours & Joules)**:

E_Wh = Capacity (Ah) × V_nominal = Capacity (mAh) × V_nominal1,000

E_Joules = E_Wh × 3,600 = Q_Coulombs × V_nominal

• **

• Standard Nominal Cell Voltages by Chemistry**:

• Lithium-Ion / Li-Po: 3.7V (range: 3.0V to 4.2V)

• Lithium Iron Phosphate (LiFePO4): 3.2V (range: 2.5V to 3.65V)

• NiMH / NiCad Rechargeable: 1.2V

• Alkaline Primary: 1.5V

• Lead-Acid Automotive (12V SLI): 12.0V to 12.6V (6 × 2.0V cells)

How to Use This Calculator

Enter your Battery Capacity Magnitude (e.g. 5.0 in capacity), From Capacity Unit — choose from Amp-Hours (Ah = 1,000 mAh), Milliamp-Hours (mAh = 10⁻³ Ah), Kiloamp-Hours (kAh = 1,000 Ah), Battery Nominal Voltage (Volts / V) (e.g. 3.7 for Li-ion, 12.0 for Lead-Acid in V), and Battery Chemistry & Device Benchmark — choose from Custom Capacity & Voltage, AA NiMH Rechargeable (2.5 Ah = 2,500 mAh @ 1.2V) → 3.0 Wh, Smartphone Li-Po Battery (5.0 Ah = 5,000 mAh @ 3.7V) → 18.5 Wh. Results update instantly as you type — adjust any value to compare scenarios.

The Formula

Formula Reference: Amp-Hour to Milliamp-Hour Converter (Ah to mAh & Battery Energy)

Input variables:

batteryCapacityMagnitudeInput — Battery Capacity Magnitude

sourceCapacityUnitSelect — From Capacity Unit

nominalVoltageVoltsInput — Battery Nominal Voltage (Volts / V)

Computed outputs:

capacityMilliampHours — Capacity in Milliamp-Hours (mAh)

capacityAmpHours — Capacity in Amp-Hours (Ah)

storedEnergyWattHours — Stored Energy in Watt-Hours (Wh)

totalElectricChargeCoulombs — Total Electric Charge (Coulombs / C)

storedEnergyKilojoules — Stored Energy in Kilojoules (kJ)

Mathematical relationships extracted from calculation logic:

mah = ah * 1000.0

coulombs = ah * 3600.0

wh = ah * volt

kj = (wh * 3600.0) / 1000.0

hoursAt500mA = ah / 0.5

Reference constants:

ah = 5.0

Standard: NIST Handbook 44 and BIPM SI unit definitions

Worked Example

A traveler checking whether their 20,000 mAh 3.7V laptop power bank is allowed on commercial passenger aircraft calculates energy as / 1,000 = 74.0 Wh, well below the TSA 100 Wh airline limit.

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.