399 / SR927W battery equivalent

Also sold as SR927W. 1.55 V with a flat discharge curve — the usual choice for quartz watches.

Chemistry

Silver oxide

Voltage

1.55 V

Size

9.5 × 2.7 mm

Inches

0.374 × 0.106 in

Drain

High drain (W)

Typical capacity

~55 mAh

Shop 399 on Amazon See in full chart

Equivalents by brand

Brand	Number
Renata	399
Energizer / Eveready	399
Maxell / Panasonic / Sony	SR927W
Varta	V399
Rayovac	399
Duracell	D399
Bulova	613
Timex	W
Citizen	280-44
Seiko	SB-BP/EP
IEC	SR57
IEC size	SR927

Also known as

SR927WV399D399613W280-44SB-BP/EPSB-BPSB-EPSR57SR927AG7

What it fits

Watches with alarms, lights, or digital features; some Casio calculators. Confirm the printed number or measure the old cell before you buy — a 0.5 mm height difference will not seat correctly.

IEC names encode chemistry and size. SR is silver oxide, LR is alkaline, and CR is 3 V lithium. The digits are diameter and height in tenths of a millimeter, so SR927W is about 9.5 mm across and 2.7 mm thick.

Same size, different drain

These cells share the 9.5 × 2.7 mm can. Low-drain (SW) is for simple analog watches. High-drain (W) handles lights, alarms, and chronographs. A modern multi-drain cell can usually cover both.

FAQ

What battery replaces a 399?

Any of these are common equivalents: 399, SR927W, V399, D399, 613, W, 280-44, SB-BP/EP. They are 1.55 V silver oxide cells, 9.5 × 2.7 mm.

Is 399 the same as SR927W?

Yes — SR927W is the IEC / Japanese-brand name for the same 399 cell.

What devices use a 399?

Watches with alarms, lights, or digital features; some Casio calculators