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Mistake guide

Equating mAh and Wh

A 5000 mAh battery holds more energy than a 4500 mAh one.

01Assumption

A 5000 mAh battery holds more energy than a 4500 mAh one.

02Actually

mAh measures charge, not energy. Energy content is Wh = Ah × volts. A 5000 mAh battery at 3.7 V stores 18.5 Wh, a 4500 mAh battery at 5 V already stores 22.5 Wh — the smaller charge figure carries more energy here.

03Why

Manufacturers advertise the larger number, and mAh is comparable as long as the cell chemistry matches. As soon as nominal voltage differs — for instance between a single cell, a power bank and a laptop battery — the comparison is worthless without the voltage.

04Check

Use the Wh figure for comparisons; it is printed on many batteries as well. If it is missing, divide mAh by 1000 and multiply by the nominal voltage. Power banks often calculate internally with the cell voltage but state the usable output at 5 V, so the figure and reality also diverge through conversion losses.

Matching conversions

Milliampere hour to Ampere hourmAh → AhElectric chargeAmpere hour to Milliampere hourAh → mAhElectric chargeMilliampere hour to CoulombmAh → CElectric chargeAmpere hour to CoulombAh → CElectric charge

Matching tables

TableBattery capacity: mAh and Wh

Unit family: Electric charge

Sources

BIPM SI BrochureSI base units, prefixes and official SI context.NIST Guide to SI Appendix BNIST conversion-factor method and non-SI factors.
When not to use

Do not use as the sole basis for official, medical, safety-critical or contractual decisions.

Citation

Citation note: UnitCloud, mistake guide, sources reviewed: September 2026. Source basis: BIPM SI Brochure · NIST Guide to SI Appendix B.