Phone makers advertise battery size in mAh (milliamp-hours). Laptops, airlines and many power banks use Wh (watt-hours). Here's the difference — and why mAh alone doesn't tell you battery life.
The simple version
- mAh measures electric charge. It only means something together with the battery's voltage.
- Wh measures energy: Wh = mAh × volts ÷ 1000.
Most phone batteries are about 3.85 V nominal, so a 5,000 mAh phone battery holds roughly 5,000 × 3.85 ÷ 1000 ≈ 19 Wh.
Why a bigger mAh number doesn't always mean longer life
Battery life depends on how much energy the phone uses, not just how much it stores:
- Screen: size, brightness and refresh rate.
- Chip efficiency: newer chips often do the same work with less power.
- Software: how well the system manages background apps.
- Signal: weak signal costs a lot of power.
That's why a phone with a smaller battery can sometimes outlast one with a bigger battery. On Zynverse we show the official capacity — and we don't invent "battery life hours" that the maker didn't publish.
Power banks: why you never get the full mAh
A power bank's mAh rating is usually measured at its internal cell voltage (about 3.7 V), but it charges your phone through USB at 5 V or more, with conversion losses. In practice you typically get around 60–70% of the printed mAh into your phone.
The airline limit
Airlines generally allow power banks up to 100 Wh in carry-on luggage without approval (rules differ by airline — always check). At 3.7 V, 100 Wh is about 27,000 mAh.
Quick comparison tips
- Comparing phones: use mAh plus charging speed, chip and screen — or the battery part of the Zynverse Score.
- Comparing power banks and laptops: use Wh.
Sources
- www.anker.com /uk/blogs/power-banks/mah-to-wh
- chargie.org /mah-vs-wh/