Thickness — 2.1 mm vs 2.6 mm
SR621SW is 2.1 mm thick; SR626SW is 2.6 mm. Holders are built for one stack height. The thinner cell loses spring pressure (“works only when I press the cover”). The thicker cell jams the door or bends the clip.
Not interchangeable
SR621SW vs SR626SW
364 vs 377: Watch Battery Height
Both are 6.8 mm wide silver oxide cells. 364/SR621SW is 2.1 mm thick; 377/SR626SW is 2.6 mm thick. Height is the entire story.
Last verified Aug 25, 2026
Are SR621SW and SR626SW interchangeable?
Not interchangeable — thickness must match the case.
A SR626SW vs SR621SW swap fails on thickness, capacity. If the door only closes when you force it, or the device works only while you press the cover, you have the wrong cell — not a weak spring you should ignore.
SR621SW vs SR626SW specs: thickness, capacity
They share 1.55 V and SilverOxide and 6.8 mm diameter, which is why SR621SW vs SR626SW looks interchangeable on a store shelf. Highlighted rows are the ones that change the purchase: thickness, capacity.
Read physical fit before capacity. Extra milliamp-hours only help when the holder is built for that cell. A “better” spec in the wrong tray is a mechanical or voltage mismatch, not an upgrade.
Difference between SR621SW and SR626SW batteries
If you searched SR626SW vs SR621SW, you are on the same comparison with the names reversed. The difference between SR621SW and SR626SW batteries is not the word “vs” — it is the specs that do not match after you ignore the similar photos.
Capacity — 18–23 mAh vs 25–30 mAh
Typical SR621SW capacity is 18–23 mAh. SR626SW is 25–30 mAh. Runtime only follows that gap inside the correct holder. Extra capacity in the wrong tray does not last longer — it often does not run at all.
Shared 6.8 mm diameter
Shared 6.8 mm diameter
2.1 mm (364) vs 2.6 mm (377)
2.1 mm (364) vs 2.6 mm (377)
Thin dress watches often need 364; many standard quartz watches use 377
Thin dress watches often need 364; many standard quartz watches use 377
How the size code works (SR621SW vs SR626SW)
Coin and button codes are rulers, not brand slogans. The letters mark chemistry class. The digits encode size. SR621SW measures 6.8 × 2.1 mm; SR626SW measures 6.8 × 2.6 mm. Once you read the code that way, SR626SW vs SR621SW stops looking like a preference and starts looking like a fit check.
Can I use a SR621SW instead of a SR626SW?
Usually no. SR621SW is 6.8 × 2.1 mm at 1.55 V (SilverOxide). SR626SW is 6.8 × 2.6 mm at 1.55 V (SilverOxide). Those are not the same part.
If the spent cell or tray said SR626SW, specify that code. Forcing SR621SW can crack a cover, lose contact, or apply the wrong voltage.
Can I use a SR626SW instead of a SR621SW?
Usually no. Going the other way does not fix a diameter, thickness, or voltage miss. SR626SW in a SR621SW holder has the same problem with the names flipped.
If you arrived from a SR626SW vs SR621SW search, stay on this page. The answer does not change.
Brand labels and aliases
Retail packs hide the IEC size behind house codes. SR621SW also appears as 364, 363. SR626SW also appears as 377, 376, SR66. Those prefixes do not change the outline unless the chemistry letters change (BR, LIR, ML, PR).
How to identify SR621SW versus SR626SW
You do not need a full datasheet to settle SR621SW vs SR626SW. You need the stamp, the tray, or a cheap pair of calipers. A store bin labeled only “button cell” or “3V lithium” will not do that work for you.
- Read the code on the old cell: SR621SW, SR626SW, and the brand prefixes that map to each one.
- If the print is worn off, check the tray, battery door, or user manual before buying.
- Measure diameter if the codes are gone: SR621SW is 6.8 mm; SR626SW is 6.8 mm.
- Measure thickness: SR621SW is 2.1 mm; SR626SW is 2.6 mm.
- Buy the matching code. Extra capacity or a thicker can only helps when the holder is built for that cell.
Choose SR621SW when…
- Chart or old cell says 364 / SR621SW
Choose SR626SW when…
- Chart says 377 / SR626SW / 376
Compatibility and substitution
A thicker 377 can prevent a thin caseback from closing. A thinner 364 can lose contact in a 377 movement.
Do not stack cells, grind a can, or use foil as a permanent spacer to fake SR626SW with SR621SW. Read the stamp, then the spec table. If the door will not close without force, you have the wrong height or diameter.
SR621SW vs SR626SW FAQ
My watch says 377 but 364 fits under the cover — OK?
Fitting under the cover is not enough. If the movement specifies 377, use 377 for reliable contact.
I searched SR626SW vs SR621SW — is this the right page?
Yes. SR621SW vs SR626SW and SR626SW vs SR621SW are the same pair. Fit, voltage, and chemistry do not change when you flip the order.
Should I always trust a cross-reference chart?
Use this guide as a starting point, then confirm voltage, chemistry, and physical size with your device manual or the marking on the old cell.
Review record and primary sources
Reviewed by PlainBattery Technical Review Desk on 2026-08-25. Checked: both model identities and dimensions, voltage and chemistry differences, physical fit, interchangeability conclusion and safety warnings.
- Silver Oxide (SR) and Alkaline Button (LR) Battery Specifications — Maxell. SR/LR model dimensions, voltage, nominal capacity and drain class.
Revision record: source citations and field-level review scope added September 11, 2026. See our sources and methodology and corrections policy.