A watch battery is named by a code, not by a brand. The same 6.8 mm silver-oxide cell is sold as SR626SW, 377, SB-A4 and 1176SO, and a shop that only stocks one of those labels will still sell you the right battery if you know how the numbers map. This page is the cross-reference: what the letters mean, which codes are interchangeable, and where the lookup usually goes wrong.
What the letters mean
Watch cells use a chemistry prefix followed by a size code.
- SR is silver-oxide. It holds a flat 1.55 V across most of its life, which is why quartz movements are designed around it. Almost every analog watch battery you will replace is an SR cell.
- LR is alkaline. It is cheaper, loses voltage steadily, and is the reason a watch can run slow for weeks before it stops. Use it only if the movement was designed for it.
- CR is lithium manganese. It delivers 3 V and is used in digital modules, backlights and connected watches, not in a standard three-hand quartz movement.
The number after the prefix is a size code, not a capacity rating. A larger number does not mean a longer-lasting battery in the abstract; it means a physically different can that will not fit the movement holder.
Cross-reference table for common watch cells
| Code | Also sold as | Diameter | Typical use |
|---|---|---|---|
| SR626SW | 377, SB-A4, 1176SO | 6.8 mm | Most three-hand quartz movements, including many Fossil, Seiko and Citizen cases |
| SR621SW | 364, SB-A6, 1171SO | 6.8 mm | Thin dress watches and fashion-brand three-hand movements |
| SR920SW | 371, SB-AN, 1170SO | 9.5 mm | Larger cases, chronographs and some field watches |
| SR927SW | 395, SB-AP, 1175SO | 9.5 mm | Chronograph modules that need more current |
| SR936SW | 394, SB-A9, 1177SO | 9.5 mm | Bigger movements and some solar-hybrid modules |
| CR2016 | DL2016 | 20 mm | Digital displays and dual-display modules |
| CR2025 | DL2025 | 20 mm | Digital panels that need a little more reserve |
| CR2032 | DL2032 | 20 mm | Connected and smartwatch modules |
Two rules follow from the table. First, SR626SW and SR621SW share a diameter but not a thickness: a 377 will not seat correctly in a movement cut for a 364, and forcing it bends the contact. Second, never substitute an LR cell for an SR cell of the same number. The size is identical and the voltage behaviour is not.
How to read the code on the old cell
Take the old cell out and read the four to six characters printed on the flat face. You will usually see one of three things:
- An SR code, such as SR626SW. Match it exactly.
- A three-digit number, such as 377. Use the table above to convert it to the SR code before ordering.
- A manufacturer code, such as SB-A4 or 1176SO. These are equivalent names for the same can; convert to the SR code to compare prices.
If the printing has worn off, read the movement caliber stamped on the plastic holder, then look up the cell for that caliber. The case back rarely lists the battery, and the watch’s model number does not determine it either: brands change movements inside the same model family without changing the case reference.
When the watch takes a CR cell
A CR cell means the watch has a digital or hybrid module. Replacing it is the same physical job as an SR cell, but the failure looks different: an analog movement with a flat cell stops or jumps in two-second steps, while a digital module can go blank, lose its backlight, or reset the time while the hands keep running. If the hands are fine and the screen is dead, the CR cell is the suspect, not the main movement.
Common cross-reference mistakes
- Matching by diameter only. 371 and 395 are both 9.5 mm; they differ in thickness and current, and swapping them changes how long the watch runs rather than whether it fits.
- Using an LR cell because it is in stock. The watch will run, then lose time for weeks before it stops — which reads as a movement fault.
- Buying by watch brand. Fossil does not make batteries, and a “Fossil battery” is an SR cell with a Fossil part number on the packaging.
- Reusing a swollen cell. If the old cell came out domed or leaking, the movement needs cleaning before a new cell goes in; otherwise the new cell shorts against the residue.
If you are working out which cell a specific watch takes, the brand guides go deeper: what a battery change costs, which case back you are opening, and setting the time and date afterwards.
Frequently Asked Questions
Is 377 the same as SR626SW?
Yes. 377 is the three-digit trade number for the SR626SW silver-oxide cell, and SB-A4 and 1176SO are further aliases. Any of those labels describes the same 6.8 mm can.
Can I use an LR626 instead of an SR626SW?
The cell will fit, but do not use it in a watch designed for silver-oxide. The alkaline version loses voltage steadily, so the watch drifts and then stops early. The correct substitute is another SR626SW from a different manufacturer.
Why does my watch take a CR2032 if it is not a smartwatch?
Some hybrid and dual-display modules use a CR cell for the digital section while the hands run from a separate source. If your watch has a screen, a backlight or Bluetooth, a CR cell is expected.
Does a higher number mean a longer-lasting battery?
No. The number is a size code. Runtime depends on the chemistry, the can thickness and the current the movement draws — a thin 371 and a thick 395 are the same diameter with different reserves.
What if the replacement cell is slightly too thick?
Stop. A cell that sits proud of the holder will not let the case back seat, and tightening it bends the movement plate or cracks the crystal. Order the exact code rather than forcing the closest size.
The We Know Watches editorial team brings together over 40 years of combined watch collecting, trading, and repair experience. Our editors have owned and handled watches from every major brand — from entry-level Seiko 5s to Rolex, Omega, Patek Philippe, and independent Swiss watchmakers. We’ve bought and sold at auction, worked with authorized dealers, visited manufacturing facilities in Switzerland and Japan, and serviced hundreds of movements ranging from the Seiko 7S26 to the Longines L888. Every guide and review we publish is based on hands-on experience, original research, and consultation with professional watchmakers. We do not accept payment for reviews, and we clearly disclose when we use affiliate links.