Every button or coin cell code is built the same way: [chemistry letter][R = round][size digits]. The first letter names the chemistry — and with it the voltage. The second letter, R, simply means the cell is round. The digits that follow carry the size.

Take the most common coin cell of all: CR2032 = C (lithium) + R (round) + 20 mm diameter + 3.2 mm height — the last two digits are the height in tenths of a millimetre. That worked example is Panasonic's own explanation of its CR codes.

• Coin diameters are nominal: the 24-series coins (CR2430, CR2450, CR2477) actually measure 24.5 mm across, not 24 mm.
• Four-digit watch and button codes only approximate the size: an LR1130 really measures 11.6 × 3.05 mm and an SR920 9.5 × 2.05 mm. Always check the dimensions, not just the code.
• Two-digit legacy codes (LR44, SR44) encode nothing at all — they are pure size codes inherited from older lists. LR44's Panasonic code, L1154, hints at the true 11.6 × 5.4 mm shape the “44” hides.

All of these cells are lithium / MnO2, 3.0 V and non-rechargeable. Capacities are Panasonic's published nominal figures unless an Energizer figure is shown; brand codes are from Maxell's official cross-reference guide.

BR cells use carbon monofluoride instead of manganese dioxide: same sizes, same 3.0 V, but built for very low continuous drain and a wider temperature window — memory backup, meters and automotive duty. Energizer's own CR2032 page lists BR2032 as a size-equivalent replacement for its CR2032.

Panasonic's high-temperature BR “A” series (BR1225A, BR1632A, BR2330A, BR2450A1, BR2477A) is rated −40 °C to +125 °C for automotive electronics, toll transponders and RFID.

Specifications are from Maxell's own LR range; cross codes are from Maxell's official cross-reference guide.

Maxell's typical uses for alkaline buttons: medical thermometers, personal alarms, LED lights and Bluetooth LE devices.

LR54 is not a separate battery — in Maxell's official guide it appears inside the LR1130 row as Panasonic's alternate code for the same cell.

Maxell builds two versions of most silver oxide sizes. SW is the low-drain, long-life type — sodium hydroxide electrolyte, roughly twice the leak-resistant life — made for analog watches. W is the high-drain type — potassium hydroxide electrolyte — for digital watches with alarms and backlights, and for medical devices. Same size, same voltage, different watch number.

Capacities are Maxell's published figures; where Maxell lists two figures for one model, both are shown — they are different variants, not a range. The last three rows are cross-checked from Renata's and Varta's tables, which publish no capacity for them here.

Silver oxide and alkaline cells come in matching sizes — LR44 ↔ SR44, LR43 ↔ SR43, LR1130 ↔ SR1130, LR41 ↔ SR41 — so each physically fits the other's holder. They are not the same battery: SR is 1.55 V against LR's 1.5 V, and silver oxide holds a flat voltage to the end of its life while alkaline voltage slopes down as it drains — which is why watches specify SR. In Maxell's own tables the SR44 also holds more: 165 mAh against the LR44's 120 mAh.

The practical rule: a device specified for SR should get SR. Putting SR into a device specified for LR is gentler — 0.05 V higher on a flat curve — and is the common upgrade path.

SR44 brand codes: Varta V303 (low-drain) / V357 (high-drain), SG13 / G13, Energizer EPX76; Duracell sells one combined 303/357 pack.

The tab colour is an industry standard printed on the pull-tab; all four sizes are 1.4 V nominal.

Brand forms: Energizer AZ10 / AZ13 / AZ312 / AZ675; Power One p10 / p13 / p312 / p675.

Handling facts from Power One:

• The tab seals the air holes — the cell activates only once the tab is removed and air enters.
• Wait a few seconds after pulling the tab before use.
• Re-sticking the tab does not restore or extend life.
• Store at 10–30 °C.
• Never carry cells loose in a pocket with coins or keys — short-circuit risk.

Every cell in these charts sits at the intersection of up to five naming systems: the IEC code, the ANSI/NEDA number, the watch-battery number, each brand's own code, and the AG/SG trade codes printed on blister packs.

Bonus quirk: Energizer's CR2430 datasheet designates the cell IEC-CR2425 — the “2430” everyone buys by is the trade name, not the designation on the maker's own sheet.

The U.S. Consumer Product Safety Commission warns that a swallowed button or coin cell “can cause serious injuries, internal chemical burns or death”. Energizer's CR2032 datasheet is blunter: serious injury or death in as little as 2 hours, from chemical burns and potential perforation of the esophagus. Seek immediate medical care, and in the U.S. call the National Battery Ingestion Hotline: (800) 498-8666.

Reese's Law and the CPSC rule at 16 CFR Part 1263 require consumer products with button or coin cells to have battery compartments secured by a tool or by two independent, simultaneous movements, plus ingestion warnings on packaging.

Storage: keep new and used cells out of children's reach, in original packaging, never loose with coins, keys or other metal. Zinc-air spares keep best at 10–30 °C with their tabs on.

Disposal: never put button or coin cells in household garbage — follow local hazardous waste procedures, and tape spent lithium coin-cell terminals before drop-off. Routes and city programs are in our battery recycling hub.

These are Amazon search links — check the code on your old cell against the charts above before ordering.