The SR416SW, sold as the 337, is one of the smallest watch batteries made: a 1.55 volt silver-oxide cell just 4.8 mm across and 1.65 mm tall, holding about 8 mAh. It powers ultra-slim ladies' watches and very small electronic devices.
SR416SW, face and side profile, drawn to scale: 4.8 mm across, 1.65 mm thick.
Voltage
1.55 V
Size (D×H)
4.8 × 1.65 mm
Chemistry
Silver oxide (Ag2O)
Capacity
8 mAh
Same battery, other names
Every code below is the exact same cell as SR416SW. Any of them will fit and work identically.
337
Buying and replacement notes
There is no alkaline stand-in at this size; the 337 is the only game in town. Handle it with plastic tweezers when changing it, both because fingers struggle with a 4.8 mm cell and because skin oils on the contacts shorten its already modest life. Expect one to two years in a simple movement.
⚠️ Keep away from children. Swallowed button batteries, especially 20 mm lithium coins, cause severe injury within hours. If a child swallows one, call the 24/7 National Battery Ingestion Hotline (US) at 800-498-8666 or poison control at 800-222-1222 immediately. What every parent should know.
Frequently asked questions
Is the 337 the same as the SR416SW?
Yes. 337 is the retail number and SR416SW the IEC designation for the identical silver-oxide cell, 4.8 mm in diameter and 1.65 mm tall, rated 1.55 V and about 8 mAh. Renata, Sony/Murata, Seizaiken and Energizer all sell it under both codes.
What devices use the 337 battery?
Mostly very slim quartz watches with small movements, plus a handful of miniature electronics such as tiny earpieces. If your watch takes a 337, no larger cell will fit; the battery recess is machined for exactly this 4.8 x 1.65 mm size.
How long does an SR416SW last?
Around one to two years in a basic analog watch. With only 8 mAh on board it is sensitive to a tired movement; if fresh batteries keep dying in months, have the watch serviced because worn gears or old oil raise current draw dramatically.