The SR621SW is a tiny 1.55-volt silver oxide watch battery, about 6.8 mm wide and 2.1 mm thick. Its most common equivalent is the 364, and Energizer sells it as a combined 364/363 cell (IEC SR60). Energizer’s battery cross-reference guide lists 364, SP364, V364, SR621SW and SG1, among other names, as the same cell.
This guide uses Energizer’s data sheets and cross-reference guide to explain what the names mean, how the 364 differs from the similar-looking 377, and what to buy for your watch.
| 364 / 363 / SR621SW | |
|---|---|
| Chemistry | Silver oxide |
| Voltage | 1.55 V |
| Diameter | 6.50-6.80 mm |
| Height | 1.90-2.15 mm |
| Typical capacity | 20-23 mAh |
| Weight | 0.31-0.37 g |
| IEC code | SR60 |
| US (ANSI/NEDA) code | 1175SO |
What is the equivalent of an SR621SW battery?
The 364, also sold as 363 or 364/363. Energizer’s cross-reference guide lists one 364/363 cell that replaces batteries labelled 364, SP364, V364, GP64, SR621SW, SG1 and Type T, among others. All of these are silver oxide cells of the same IEC size, SR60.
Alkaline cells of this size use codes that start with “L” instead of “S” (for example LR621). They are 1.5 volts instead of 1.55 V, and Energizer’s silver oxide manual says silver oxide holds its voltage more steadily, which is why watches usually use the silver oxide version.
364 vs 363: what is the difference?
Very little. Both are silver oxide SR60 cells of the same size with the same ANSI code (1175SO), and Energizer sells them as one 364/363 battery. Energizer’s 364 data sheet describes it as designed for continuous low drain, and its 364/363 sheet adds “high pulse on demand”, the kind of use found in watches with a light or alarm. If your old battery says 363, a 364/363 cell fits.
What does SR621SW mean?
- S: silver oxide chemistry
- R: round
- 621: the size, roughly 6.8 mm wide (shown as “6”) and 2.1 mm thick (“21”)
- SW: a maker’s suffix; some brands sell SW and W versions of the same size, so match the letters on your old battery if you can
SR60 is the IEC name for the same size. Numbers like 364 and 363, and names like SG1, are maker and retail codes.
Is 364 the same as 377?
No. They are the same width, about 6.8 mm, but the 377 (SR626SW) is thicker: about 2.6 mm against about 2.1 mm for the 364. A 377 will not fit a 364 slot, and a 364 in a 377 slot may sit loose and lose contact. Always match the number on your old battery. Our SR626SW and 377 guide covers the thicker cell.
How long does a 364 battery last?
In Energizer’s continuous low-drain test (68,000 ohms, about 0.02 mA), the 364 ran about 870 hours to 1.3 V and the 364/363 about 1,045 hours to 1.2 V. Real battery life depends on the watch and how often you use features like a light or alarm. Energizer’s 364 sheet also shows the voltage staying near 1.55 V until late in the battery’s life, which is typical of silver oxide.
Where 364 batteries are used
Energizer’s cross-reference guide lists watches as the main use for the 364/363 size. Before you buy, check the code on the old battery or in your watch’s manual, because many watch batteries look alike.
Button battery safety
Small button batteries are dangerous if swallowed. Keep new and used cells away from children and pets, and get emergency medical help straight away if you think a child has swallowed one.
More battery guides: SR626SW and 377 equivalents, LR41 equivalents, LR1130 equivalents and the CR1220 coin cell.
Need a wider watch battery? Our SR920SW and 371 equivalent guide covers the 9.5 mm silver oxide cell sold as 371, 370 and SG6.
For a larger watch cell, see our SR927SW and 395 equivalent guide.
Frequently asked questions
Is SR621SW the same as 364?
Yes. Energizer’s cross-reference guide lists SR621SW as one of the names for its 364/363 silver oxide cell.
Can I use 377 instead of 364?
No. A 377 is the same width but about 0.5 mm thicker, so it will not fit a watch made for a 364.
Is SG1 the same as SR621SW?
Yes. SG1 is listed alongside SR621SW and 364 in Energizer’s cross-reference guide.
What size is a 364 battery?
About 6.8 mm (0.27 in) across and 2.1 mm (0.08 in) thick. Energizer’s data sheet gives 6.50-6.80 mm by 1.90-2.15 mm.
What voltage is a 364 battery?
1.55 volts. It is a silver oxide cell.
Is 363 the same as 364?
Yes, for buying purposes. They share the same size, IEC code and ANSI code, and Energizer sells them as one 364/363 cell.
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