How quartz watch battery life is estimated
A quartz watch draws a tiny, steady current to keep the quartz crystal oscillating and step the motor once a second. A simple three-hand movement uses roughly 1 – 1.5 microamps (µA). The battery's capacity, in milliamp-hours (mAh), divided by that current gives the theoretical life. In practice the cell can't be fully used before its voltage drops, and silver-oxide cells slowly self-discharge, so real life is shorter.
Battery life (hours) = usable capacity (mAh) × 1000 ÷ average current (µA)
For example, a 26 mAh SR626SW in a watch drawing 1.2 µA lasts a little over 2 years in theory and slightly less in practice once usable capacity and self-discharge are included – which is why many watch batteries are changed every 2 – 3 years.
Common watch batteries
| IEC name | Common codes | Size (mm) | Approx. capacity |
|---|
| SR621SW | 364, AG1 | 6.8 × 2.1 | ~20 mAh |
| SR626SW | 377, AG4 | 6.8 × 2.6 | ~26 mAh |
| SR916SW | 373 | 9.5 × 1.6 | ~29 mAh |
| SR920SW | 371, AG6 | 9.5 × 2.05 | ~44 mAh |
| SR927SW | 395, AG7 | 9.5 × 2.7 | ~55 mAh |
| CR2025 / CR2032 | lithium | 20 × 2.5 / 3.2 | ~160 / 225 mAh |
"SW" cells are designed for low-drain analog watches; "W" cells (e.g. SR626W) handle higher pulses for digital watches with backlights and alarms. Check the code printed on the old battery or in the watch manual.
What drains a watch battery faster
- Chronographs: a running chronograph can multiply consumption many times over.
- Backlights and alarms: a few seconds a day can use more energy than the timekeeping itself.
- Temperature: cold reduces available capacity; heat speeds up self-discharge.
- Old or stored batteries: a cell that sat in a drawer for years has already lost capacity.
Changing the battery
Many jewelers and watch shops replace batteries for $10 – $25 while you wait. For water-resistant and dive watches, have the gaskets checked and the case pressure tested afterwards. Luxury brands often require battery changes at a service center, which costs more but includes a check of the movement. When storing a quartz watch for a long time, consider having the battery removed to avoid leakage.
Alternatives
Solar-powered and kinetic watches recharge themselves, and their rechargeable cells typically last 10 – 20 years. Lithium-powered quartz watches with large CR-type cells can run 5 – 10 years between changes.
Frequently asked questions
How long does a watch battery last?
Typically 2 – 3 years in an analog quartz watch, 1 – 2 years in chronographs used often, and 5 – 10 years in watches with large lithium cells.
What battery does my watch need?
Look at the code on the old battery (e.g. SR626SW or 377) or in the manual. Matching size and chemistry is essential.
Can I use an LR battery instead of SR?
It may fit, but alkaline LR cells have lower, unstable voltage and shorter life. Silver-oxide SR cells are recommended.
Why does my watch second hand jump every 2 or 4 seconds?
Many quartz movements do this to signal that the battery is almost empty.
Should I remove the battery when storing a watch?
For storage longer than a year, yes – a dead battery can leak and damage the movement.
About CellLife
CellLife is an independent, free calculator for estimating battery life in quartz analog and digital watches. Capacities and current draws are typical values; your watch's exact figures may differ. We are not affiliated with any battery or watch manufacturer.
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The methodology combines widely published engineering rules of thumb, manufacturer data sheets and the electrical code practices that installers use every day. We review the assumptions regularly and update the calculator when typical product specifications change.
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