SR626SW / 377 Battery Equivalent
The SR626SW is the world's most common watch battery. Here's every equivalent name and what you need to know before buying a replacement.
Quick answer
377, D377, V377, SR66, AG4, and LR626 are all the same physical size as the SR626SW — 6.8mm diameter × 2.6mm height.
For watches, always choose the silver oxide version (labelled SR626SW, 377, D377, V377). The alkaline version (LR626, AG4) is cheaper but causes watches to lose time due to its dropping voltage.
Specifications
Common uses: analog quartz watches, calculators, laser pointers, small electronic toys, glucose monitors, digital thermometers.
All SR626SW equivalents
Every battery listed below is 6.8mm × 2.6mm and a direct replacement for the SR626SW. The different codes are simply different manufacturers' names for the same battery.
| Code | Brand / Standard | Chemistry | Notes |
|---|---|---|---|
| SR626SW | IEC standard | Silver oxide | The international standard name. ✅ Best for watches. |
| 377 | Energizer / Renata | Silver oxide | Most widely used code globally. ✅ Best for watches. |
| D377 | Duracell | Silver oxide | Duracell's designation. ✅ Best for watches. |
| V377 | Varta | Silver oxide | Varta's designation. ✅ Best for watches. |
| SR66 | IEC short code | Silver oxide | Shortened IEC code. Same battery. |
| SB-AW | Seiko | Silver oxide | Seiko's internal code for the low-drain 377. |
| 280-39 | Citizen | Silver oxide | Citizen's internal designation. |
| AG4 | Generic / Asian | Alkaline | ⚠️ Alkaline version — avoid for watches. |
| LR626 | IEC standard | Alkaline | ⚠️ Alkaline version — voltage drops, causes timekeeping errors. |
| LR66 | IEC short code | Alkaline | ⚠️ Same as LR626. Not recommended for watches. |
| 376 | Energizer | Silver oxide | High-drain version. Modern 376/377 multi-drain cells cover both. |
| SR626W | IEC standard | Silver oxide | High-drain variant. Multi-drain cells now cover SW and W. |
⚠️ Silver oxide vs alkaline — this matters for watches
SR626SW (silver oxide) maintains a steady 1.55V throughout its entire life, then drops sharply at the end. This flat voltage curve is essential for accurate timekeeping in quartz watch movements.
LR626 / AG4 (alkaline) starts at 1.5V and gradually declines. This dropping voltage causes quartz watches to lose seconds per day, getting progressively worse as the battery ages.
Alkaline LR626 batteries are cheaper, but always use silver oxide (SR626SW / 377) in watches. For non-watch devices like calculators and toys, either chemistry works fine.
⚠️ Don't confuse SR626SW (377) with SR621SW (364)
These two batteries have the same 6.8mm diameter but different heights — SR626SW is 2.6mm tall and SR621SW is 2.1mm tall. That 0.5mm difference means they are not interchangeable.
An SR621SW placed in an SR626SW slot may make unreliable contact. An SR626SW forced into an SR621SW slot may not fit or could damage the battery compartment. Always check the code printed on your existing battery before buying.
Watches that use the SR626SW / 377
The 377 is the single most common watch battery in the world. If your analog quartz watch has stopped and you're not sure which battery it needs, there's a good chance it's this one. Here are some of the most popular watches that use it:
Not sure? Open the caseback and check the code printed on the existing battery. If you see 377, SR626SW, D377, V377, or SR66, this is your battery.
A note from our watch expert
In nearly 40 years in the jewellery trade, the 377 is the battery I've replaced more than any other — by a huge margin. It fits the vast majority of analog quartz watches from budget to mid-range. If a customer brings in a watch and doesn't know the battery, this is almost always the first one I check.
One tip: always use a quality silver oxide cell from Renata, Energizer, or Maxell. Cheap alkaline AG4 cells from market stalls will work for a few months but the watch will gradually lose time. It's a false economy.
Frequently asked questions
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