How to read the code stamped on a coin cell battery
Turn the cell over before you buy a replacement. The engraving is a size, a chemistry and a polarity, and it is the only reference that never goes out of date.
The code engraved on a coin cell reads left to right. The first letter is the chemistry, C for lithium manganese dioxide, B for lithium carbon monofluoride, S for silver oxide, L for alkaline. R means round. Then the digits: diameter in millimetres, then height in tenths of a millimetre. A CR2032 is 20 by 3.2 mm.
What is actually stamped on a coin cell?
Less than you might expect. A coin cell has no paper label, because both faces are electrical contacts. The European Portable Battery Association's marking guidelines make the point directly: ink on a button cell could insulate it from the device's contacts, so anything on the cell is engraved into the metal. The same guidelines say the IEC standards expect two things on the cell itself, for safety and performance reasons: the plus sign and the designation. Everything else tends to live on the packet.
| Marking | Where you find it | What it tells you |
|---|---|---|
| Designation, such as CR2032 | On the cell, usually the flat positive face | Chemistry, shape and size. The one marking to copy down. |
| Plus sign | On the cell | Which face is positive. On a coin cell it is the wide flat face of the can. |
| Brand name and nominal voltage | Often on the cell, sometimes only on the pack | Who made it, and 3 V or 1.5 V at a glance |
| Date or lot code | On the cell for some makers, on the pack for others | Age, in whatever format that maker uses |
| Crossed-out wheelie bin symbol | The packet | Do not throw it in household waste (EU rule) |
The wheelie bin is the one people look for and never find. Under the EU Batteries Directive the symbol may move to the packaging when it would be smaller than 0.5 by 0.5 cm on the battery, and for button cells the EPBA recommends a 1 by 1 cm symbol on every pack instead.
What does the first letter on a battery code mean?
It names the electrochemical system. IEC 60086-1, the general standard for primary batteries, assigns one letter per system in its Table 1. These are the ones you will meet on coin and button cells:
| First letter | Chemistry (IEC 60086-1) | Nominal voltage | Example in our catalogue |
|---|---|---|---|
| C | Lithium, manganese dioxide | 3.0 V | CR2032, 20 x 3.2 mm |
| B | Lithium, carbon monofluoride | 3.0 V | BR2032, 20 x 3.2 mm |
| S | Zinc, silver oxide | 1.55 V | SR626SW, 6.8 x 2.6 mm |
| L | Zinc, manganese dioxide, alkaline electrolyte | 1.5 V | LR44, 11.6 x 5.4 mm |
| P | Zinc air | 1.4 or 1.45 V | Hearing aid cells |
The letter matters more than the digits. A BR2032 and a CR2032 share a case exactly, yet the chemistry differs, and CR2032 vs BR2032 explains when that changes anything.
One trap. IEC 60086 covers primary, single use batteries only, so the rechargeable prefixes are not in that table at all. The L in LIR does not mean alkaline. An LIR2032 is a 3.6 volt lithium-ion cell in the CR2032's case, and an ML2032 is a 3 volt rechargeable. If the stamp starts with LIR, ML or VL, read the rechargeable coin cell guide before buying anything.
How do you read the numbers on a coin battery?
On lithium coins the four digits split in two. The first pair is the diameter in whole millimetres, the second the height in tenths. Panasonic's CR2032 datasheet lists a maximum diameter of 20.0 mm and a maximum height of 3.2 mm, so the code describes the largest the cell may be, not a rough average.
Fractions get dropped from the diameter. Our CR1220 record is 12.5 mm across and 2.0 mm tall, and the CR2450 is 24.5 by 5.0 mm. Siblings make the scheme easy to see: CR2025 is 20 by 2.5 mm and CR2016 is 20 by 1.6 mm, the same face in three thicknesses. A cell 0.7 mm too thin will often sit loose, which is the whole story of CR2032 vs CR2025.
Watch cells and the old alkaline buttons do not read so cleanly. SR626SW is 6.8 mm across, so only the height, 2.6 mm, comes straight off the code, and the 44 in LR44 is a legacy number rather than a measurement. Those histories belong to the battery naming guide, which also covers the ANSI and AG names you will see on packets but rarely on the cell.
What do SW and W at the end mean?
On silver oxide watch cells, a trailing W marks a cell built to the IEC high drain requirements, and SW a low drain cell for simple analogue movements. Copy the suffix along with the rest of the code. The watch battery guide explains what happens when the drain rating does not match the movement.
How do you read the date code on a battery?
Honestly, there is no common key. Some makers engrave a lot or date code on the cell, others print an expiry date only on the packet, and each uses its own format. We do not publish a decoder because no shared one exists to cite. If you need the age, keep the packet, or check the maker's own site for its format.
What if the code has worn off?
Measure, then check the voltage. Calipers give diameter and height, and the battery size chart maps those to codes. A meter separates the 3 volt lithium coins from the 1.5 volt family. It cannot reliably tell silver oxide from alkaline, though, and it cannot tell a CR from a BR cell, so if the device's manual or the old packet names the cell, trust that over your measurements.
And if a loose cell turns up anywhere small hands can reach, deal with that before the code. Our button battery child safety guide explains why.