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Comparison

CR123A vs CR2

The CR123A and CR2 are cousins from the film camera era: both 3 volt lithium cylinders with ten-year shelf lives and strong cold performance. The CR123A is larger, 17 by 34.5 mm with about 1500 mAh, while the CR2 measures 15.6 by 27 mm with about 800. They are never interchangeable.

CR123A and CR2 drawn side by side at the same scale: CR123A is 17 mm across, 34.5 mm tall; CR2 is 15.6 mm across, 27 mm tallCR123ACR2 CR123A 34.5 mm ⌀ 17 mm CR2 27 mm ⌀ 15.6 mm
CR123A vs CR2 at the same scale: 17 mm across, 34.5 mm tall against 15.6 mm across, 27 mm tall.
CR123ACR2
ChemistryLithium manganese dioxide (Li/MnO2)Lithium manganese dioxide (Li/MnO2)
Voltage3 V3 V
Diameter17 mm15.6 mm
Height34.5 mm27 mm
Capacity1500 mAh750-850 mAh
Also sold asCR123, 123, DL123A, EL123APDLCR2, ELCR2, KCR2, CR15H270

Confusion between these two is common because the names sound sequential and the cells look like siblings. In hand, the CR123A is visibly fatter and 7.5 mm longer. Neither will seat in a device built for the other: the CR2 rattles uselessly in a CR123A tube, and the CR123A simply does not fit the smaller bay.

Their markets diverged after film. The CR123A became the standard of tactical flashlights, alarm and security sensors, smart locks and night vision, where its energy density and pulse delivery shine. The CR2 found a durable niche in laser rangefinders for golf and hunting, plus compact film cameras and some older Instax models. Check your device's manual or the old cell; the two ecosystems barely overlap.

Both sizes have rechargeable lookalikes (16340 for the CR123A, 15270/RCR2 for the CR2) at 3.6 to 3.7 volts. Device support for these varies from full to none, so verify before substituting, and stick to primaries in safety devices like alarm sensors and smoke detectors.

All about CR123A All about CR2

Frequently asked questions

Is the CR2 just a smaller CR123A?
Chemically yes, both are 3 V lithium manganese dioxide with similar shelf life and temperature range. Physically no: at 15.6 x 27 mm the CR2 is a different size class than the 17 x 34.5 mm CR123A, holds about half the energy, and fits entirely different devices.
My rangefinder battery died on the course. Can I borrow a CR123A from my flashlight?
No. The CR123A is too fat and too long for a CR2 bay; it physically cannot be installed. Rangefinders take the CR2 almost universally, so keep a spare CR2 in the golf bag. It stores for a decade, so it will be alive when needed.
Which battery should I standardize on for emergency gear?
The CR123A, if your gear allows choosing. Its ecosystem of flashlights, sensors and radios is far larger, its capacity is roughly double the CR2's, and multi-cell devices are common. Buy reputable brands only; counterfeit CR123As are a genuine safety problem in multi-cell lights.

⚠️ 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.