Battery Size Finder
Measure the old cell across the face and through the thickness, enter both, and every one of the 84 cells that matches comes back with its chemistry, its voltage and the verdict for swapping between them.
Find a cell by size
Measure the old cell across the flat face and through the thickness, then enter both. A cell marked CR2032, for example, measures 20 mm by 3.2 mm.
Measuring the cell
A button cell is identified by two measurements and nothing else: the diameter across the flat face, and the height through the thickness. Callipers give both in a second and cost very little. A steel rule will do if you are careful: lay the cell flat and read the widest point across the face, then stand it on edge against the rule for the thickness.
Measure the cell, not the hole it came out of. Battery holders are made with clearance so the cell can be got back out, so a measurement of the recess will read large, sometimes by half a millimetre, which is enough to land you on the wrong row.
Round to the nearest tenth of a millimetre. The chart separates sizes that differ by as little as 0.1 mm, which is why the finder works to a tolerance rather than an exact match.
When more than one cell matches
That is normal and it is the useful case. Chemistries share case sizes: LR44, SR44 and the 675 hearing-aid cell are all 11.6 × 5.4 mm, and they are not interchangeable in the way their measurements suggest. The finder puts the verdict beside each pair rather than leaving you to guess from the numbers.
As a rule: in a watch, a meter or anything medical, take the silver-oxide cell. In a toy or a light, the alkaline one is fine and cheaper. A hearing-aid cell belongs only in a hearing aid, whatever its dimensions say.
If nothing matches
Widen the tolerance first: a rule measurement can easily be out by 0.3 mm. If the cell is still not here, it may be a size this chart does not cover, or a cylindrical cell rather than a button cell. Where the printing is still legible, the code decoder will read it and say what the letters and digits mean, even for a code with no page here.
Measuring and matching
- How do I measure a button battery?
- Two numbers: the diameter across the flat face and the height through the thickness. Callipers are ideal; a steel rule works if you measure the face at its widest point and then stand the cell on edge. Measure the cell, not the recess it came out of, because a holder has clearance.
- How accurate does the measurement need to be?
- A tenth of a millimetre separates some sizes, so the finder works to ±0.2 mm by default. If nothing comes back, widen the tolerance rather than guessing, and check the result against the code printed on the cell where there is one.
- Two cells came back for my measurement. Which do I buy?
- 43 of the cells in this chart share their exact size with at least one other cell, usually in a different chemistry. The finder states the verdict for each pair: silver oxide over alkaline in a watch or a meter, and never a zinc-air hearing-aid cell in place of either.
- Why does the code on my cell not match its measurement?
- In a four-digit code the first two digits are the diameter rounded down to the whole millimetre, so a CR1220 measures 12.5 mm across rather than 12.0 mm. Short codes such as LR44 are reference numbers and describe nothing at all.