Battery Capacity Converter

Convert battery capacity between µAh, mAh, Ah, and coulombs for battery datasheets, portable electronics, embedded devices, and early power-budget calculations.

This converter handles charge capacity only. It does not convert to watt-hours because energy conversion also requires battery voltage.

Engineering tool

Battery Capacity Converter

Convert battery capacity between µAh, mAh, Ah, and coulombs using charge-based engineering units.

Capacity

Battery capacity value to convert. Zero is allowed for reference conversion.

Converted Capacity

3 Ah

1 Ah equals 3,600 coulombs of electric charge.

Result console

Capacity: 3,000,000µAh
Capacity: 3,000mAh
Capacity: 3Ah
Charge: 10,800C
Formula used: Ah = mAh / 1000; µAh = mAh × 1000; C = Ah × 3600

Battery capacity is charge storage, not power or energy. Use Wh when voltage-dependent battery energy is required.

Formula reference

Battery Capacity Conversion Formulas

Battery capacity conversion uses amp-hours as the internal base unit. Coulombs are included because they are the SI unit of electric charge.

Ah = mAh / 1000mAh = Ah × 1000µAh = mAh × 1000C = Ah × 3600

Variable definitions

Capacity: Battery charge capacity
Ah: Amp-hour, the common engineering battery-capacity unit
mAh: Milliamp-hour, equal to 0.001 Ah
µAh: Microamp-hour, equal to 0.000001 Ah
Coulomb: SI unit of electric charge
1 Ah: 3600 C

Variable Description

Capacity: The amount of charge a battery can deliver under specified conditions.
Ah: Amp-hour, commonly used for larger cells and battery packs.
mAh: Milliamp-hour, commonly used for portable electronics and small cells.
µAh: Microamp-hour, useful for tiny cells, leakage budgets, and ultra-low-power devices.
Coulomb: The SI unit of electric charge; 1 Ah equals 3600 coulombs.

Worked Examples

3000 mAh

3000 mAh = 3 Ah = 3,000,000 µAh = 10,800 C

2 Ah

2 Ah = 2000 mAh = 2,000,000 µAh = 7200 C

500 µAh

500 µAh = 0.5 mAh = 0.0005 Ah = 1.8 C

Battery Capacity

Battery capacity describes stored charge, usually under a rated discharge condition.

Charge Storage

Charge capacity tells how much current can be delivered over time before reaching the cutoff condition.

Ah vs mAh

Ah and mAh express the same physical quantity at different scales.

Microamp-Hour

µAh values are useful in coin-cell, leakage, standby, and ultra-low-power calculations.

Coulomb

Coulombs are SI charge units and connect battery capacity to fundamental electrical units.

Nominal Capacity

Nominal capacity is often a typical or rated value, not a guaranteed capacity in every application.

Rated Capacity

Rated capacity depends on test current, temperature, battery chemistry, and cutoff voltage.

Capacity Tolerance

Real cells vary by manufacturing tolerance, age, temperature, and discharge rate.

Battery Chemistry

Lithium-ion, NiMH, alkaline, and lead-acid batteries can have different usable capacity behavior.

Common Mistakes

Treating mAh as mA

Confirm whether the design question involves charge, current, power, or energy before selecting units.

Treating capacity as power

Confirm whether the design question involves charge, current, power, or energy before selecting units.

Ignoring the difference between Ah and Wh

Confirm whether the design question involves charge, current, power, or energy before selecting units.

Confusing charge with energy

Confirm whether the design question involves charge, current, power, or energy before selecting units.

Comparing battery capacity without considering voltage

Confirm whether the design question involves charge, current, power, or energy before selecting units.

Assuming rated capacity is always fully usable

Confirm whether the design question involves charge, current, power, or energy before selecting units.

Support reference

FAQ

What is battery capacity?

Battery capacity is the amount of electric charge a battery can deliver under specified rating conditions. It is commonly expressed in Ah, mAh, or µAh.

What is the difference between Ah and mAh?

Ah means amp-hour and mAh means milliamp-hour. One amp-hour equals 1000 milliamp-hours.

How many coulombs are in 1 Ah?

One amp-hour equals 3600 coulombs because one ampere is one coulomb per second and one hour has 3600 seconds.

Does a higher mAh always mean longer runtime?

Not by itself. Runtime also depends on load current, cutoff voltage, temperature, discharge rate, battery chemistry, and usable capacity.

What is rated battery capacity?

Rated capacity is the capacity measured by the manufacturer under defined discharge current, temperature, and cutoff-voltage conditions.

Can this converter be used for lithium batteries?

Yes. The Ah, mAh, µAh, and coulomb conversions are charge-unit conversions and can be used with lithium cells, NiMH cells, lead-acid batteries, and battery packs.

Is Ah the same as Wh?

No. Ah is electric charge, while Wh is energy. To estimate Wh, battery voltage must also be included.

Is mAh the same as mA?

No. mAh is capacity over time, while mA is current. Confusing the two is a common battery sizing mistake.

Related Engineering Guides

Planned Engineering Guide

Understanding Battery Capacity

Planned Engineering Guide

Ah vs mAh

Planned Engineering Guide

Battery Capacity vs Energy

Planned Engineering Guide

How Battery Capacity Is Rated

Battery Life Calculator

Estimate battery life, required capacity, and average current from duty cycle.

Battery Energy Calculator

Calculate battery energy, required capacity, or nominal voltage from Wh, Ah, mAh, and voltage.

Battery Runtime Calculator

Estimate runtime and required capacity from Active, Idle, and Sleep duty-cycle load profiles.

Power Calculator

Calculate voltage, current, or electrical power from P = V × I.

Battery Charging Time Calculator

Estimate battery charging time, required charging current, or added capacity from SOC and efficiency.

Battery Discharge Calculator

Estimate discharge time, remaining usable capacity, or runtime-based average current from SOC and load current.

Engineering Disclaimer

This converter performs charge-unit conversions only. It does not predict runtime, available energy, charging time, battery aging, usable capacity, cutoff voltage, or chemistry-specific behavior.