CR123A vs 18650
A single 3.6 V rechargeable 18650 against 3 V single-use CR123A cells. Two CR123A approximate one 18650 in length, which is why many torches accept either.
Last reviewed
These are different cells, but a lot of torches accept both, and there is a reason. Two CR123A cells stacked end to end come out close to the length of a single 18650, and their diameters are within a millimetre. So a tube cut for one 18650 often takes two CR123A instead. The catch is voltage: two CR123A in series give 6 volts against the 18650's 3.6, so this only works where the manufacturer says it does. Check the manual, not the tape measure.
- Verdict:
- Many torches take either — two CR123A stack to an 18650's length
- Interchangeable:
- no
Side-by-side specifications
| Specification | CR123A | 18650 |
|---|---|---|
| Chemistry | Lithium | Li-ion |
| Type | Cylindrical | Cylindrical |
| Nominal voltage | 3 V | 3.6 V |
| Diameter | 17 mm | 18 mm |
| Height | 34.5 mm | 65 mm |
| Typical capacity | 1400–1600 mAh | 2000–3500 mAh |
| Rechargeable | No | Yes |
| Also sold as | CR17345, DL123A, EL123A, 123 | INR18650, ICR18650, NCR18650 |
Size comparison
These cells do not share a footprint, so one will not sit correctly in the other's compartment.
Why the tube fits both
A CR123A is 17 × 34.5 mm. Two end to end run about 69 mm against the 18650's 65 mm, at 17 mm across against 18 mm. Torch designers exploit that deliberately.
The voltage is not the same
Two CR123A in series deliver 6 V; one 18650 delivers 3.6 V. Only a driver designed for that range handles both, which is why the option has to be stated by the manufacturer.
Rechargeable against single-use
The 18650 recharges. The CR123A does not and must never go in a charger. For a torch used often the 18650 is cheaper to run; for one kept in a drawer for emergencies, the CR123A's shelf life wins.
Check before you stack
Two CR123A in a tube built for one 18650 puts 6 V into a driver expecting 3.6. Where a manufacturer lists both, the driver handles the range. Where it does not, the fact that they fit means nothing, and this is a swap that has destroyed plenty of torches.
Never mix old and new primaries in series
Two CR123A in series discharge together, and if one is older the stronger cell can drive the weaker into reverse. In a lithium primary that is a genuine venting risk. Replace both at once, from the same pack, or use the single rechargeable instead.
Cost over time
A torch used weekly burns through CR123As quickly and each one is expensive. The same light on an 18650 costs more up front for a cell and a charger, then almost nothing. A torch kept in a drawer for emergencies reverses that, because primaries hold their charge for a decade.
Can I use an 18650 instead of a CR123A?
Not directly. The 18650 measures 18 × 65 mm against 17 × 34.5 mm for the CR123A, so it will not seat properly in the same compartment.
Check before you swap. Batteries with similar dimensions are not always interchangeable. Always verify voltage, chemistry and the requirements printed in your device manual before fitting a replacement.
CR123A vs 18650: common questions
Is the 18650 a direct replacement for the CR123A?
These are different cells, but a lot of torches accept both, and there is a reason. Two CR123A cells stacked end to end come out close to the length of a single 18650, and their diameters are within a millimetre. So a tube cut for one 18650 often takes two CR123A instead. The catch is voltage: two CR123A in series give 6 volts against the 18650's 3.6, so this only works where the manufacturer says it does. Check the manual, not the tape measure.
What is the difference between the CR123A and the 18650?
A single 3.6 V rechargeable 18650 against 3 V single-use CR123A cells. Two CR123A approximate one 18650 in length, which is why many torches accept either. In short: many torches take either — two CR123A stack to an 18650's length.
Are the CR123A and the 18650 the same size?
No. The CR123A is 17 × 34.5 mm and the 18650 is 18 × 65 mm.
Which lasts longer, the CR123A or the 18650?
The 18650. It is rated at 2000–3500 mAh against 1400–1600 mAh for the CR123A — roughly 1.8× the capacity, though real runtime depends on how much current your device draws.
Is the 18650 rechargeable?
Yes, and the CR123A is not. Never put a CR123A in a charger: single-use cells can vent, leak or catch fire when charged.
Background reading
The wider questions behind these two codes.
Lithium for cold, weight and high drain; alkaline for everything else
Different voltages for different jobs — rarely a real choice
LiFePO4 for longevity and safety, standard lithium-ion for energy per kilo
The same chemistry in a different package