Button Battery Size Finder
The code has worn off your old battery? Measure its diameter and thickness, enter the numbers and the tool shows the closest matching button cells with their voltage and common names.
Identify your battery by size
Measure in millimetresHow to identify a button battery
- Remove the old battery. Note which side faced up before you lift it out.
- Measure the diameter. Lay the cell flat and measure across the widest point in millimetres.
- Measure the thickness. Close the caliper jaws on the two flat faces.
- Enter both numbers. The tool finds the nearest standard size.
- Check the voltage. A car key uses a 3 V lithium cell. Watches and toys often use 1.5 V cells.
To identify a button battery with no readable code, measure its diameter and thickness in millimetres. For 3 V lithium cells the code is the size: 20 mm by 3.2 mm is a CR2032, and 16 mm by 2.0 mm is a CR1620. For 1.5 V cells, match the size to a chart: 11.6 mm by 5.4 mm is an LR44.
Old coin cells lose their markings. The print rubs off in a pocket, or a leaking cell stains the face. As long as you can measure the battery, you can still name it. The size finder above does the matching for you and lists the other names the same cell is sold under.
Button Battery Size Chart
These are the cells you are most likely to find in car keys, remotes, watches, toys and small electronics.
| Code | Diameter | Thickness | Voltage | Common use |
|---|---|---|---|---|
| CR2032 | 20 mm | 3.2 mm | 3 V | Most key fobs, PC motherboards, trackers |
| CR2025 | 20 mm | 2.5 mm | 3 V | Slim key fobs, remotes |
| CR2016 | 20 mm | 1.6 mm | 3 V | Thin key fobs, often two cells |
| CR1632 | 16 mm | 3.2 mm | 3 V | Some Toyota and Subaru smart keys |
| CR1620 | 16 mm | 2.0 mm | 3 V | Honda, Subaru and Mazda keys |
| CR1616 | 16 mm | 1.6 mm | 3 V | Older Honda remote head keys |
| CR1220 | 12.5 mm | 2.0 mm | 3 V | Small remotes, glucose meters |
| CR2430 | 24.5 mm | 3.0 mm | 3 V | Larger remotes |
| CR2450 | 24.5 mm | 5.0 mm | 3 V | Newer flat smart keys |
| LR44 (AG13, A76) | 11.6 mm | 5.4 mm | 1.5 V | Toys, calculators, laser pointers |
| LR43 (AG12) | 11.6 mm | 4.2 mm | 1.5 V | Calculators, thermometers |
| LR1130 (AG10) | 11.6 mm | 3.1 mm | 1.5 V | Calculators, small toys |
| LR41 (AG3) | 7.9 mm | 3.6 mm | 1.5 V | Thermometers, small lights |
| SR626SW (377) | 6.8 mm | 2.6 mm | 1.55 V | Watches |
For a chart that covers only car key cells, with brand examples, see the key fob battery size chart.
How to Measure a Button Battery
A digital caliper is the right tool. Basic ones are inexpensive and read to 0.1 mm, which is enough to tell a CR2025 from a CR2032.
- Set the caliper to millimetres and zero it with the jaws closed.
- Close the jaws across the widest part of the cell for the diameter.
- Close the jaws on the two flat faces for the thickness. Do not squeeze hard.
- Round to the nearest standard size. A reading of 19.9 mm is a 20 mm cell.
Without a caliper, a ruler will give you the diameter. For the thickness, compare the cell with a known battery, or stack it against a coin of known thickness.
Lithium, Alkaline or Silver Oxide?
Size alone does not tell you the voltage. Two clues help:
- Shape. Lithium coin cells are wide and thin, like a coin. Alkaline and silver oxide button cells are narrow and tall, like a small pill.
- The device. Car keys, garage remotes and trackers use 3 V lithium cells. Watches, toys and thermometers usually use 1.5 V cells.
Do not replace a 3 V cell with a 1.5 V one or the other way round, even if you find one that fits. The lithium coin battery guide covers the chemistry and safe handling.
If the Battery Came From a Car Key
You have two faster options. Look up the car in the key fob battery finder, or check the owner’s manual under keys and remotes. If the shop does not stock your exact size, use the coin battery cross reference to see which other names mean the same cell.
Safety Note
Button batteries are dangerous if swallowed, especially the 20 mm lithium sizes. Keep new and used cells away from children, tape over the faces of used cells before recycling them, and seek emergency medical help at once if a cell may have been swallowed.
Frequently Asked Questions
Measure the diameter and thickness in millimetres and match them to a size chart. For lithium cells the size gives the code directly, so 20 mm by 3.2 mm is a CR2032.
On a lithium CR cell, the first two digits are the diameter in millimetres and the last two are the thickness in tenths of a millimetre. CR2025 is 20 mm wide and 2.5 mm thick.
Yes. They are different names for the same 11.6 mm by 5.4 mm, 1.5 volt alkaline button cell. The silver oxide version is sold as SR44 or 357.
A ruler is fine for the diameter. It is not accurate enough for the thickness, where 0.7 mm separates a CR2025 from a CR2032. Use a caliper if you can.
The CR2032. The next most common are the CR2025, CR2016, CR1620 and CR2450.
