18650 battery size
18 × 65 mm
3.7 V · Lithium-ion · Cylindrical · also sold as NCR18650, INR18650
About the 18650
The rechargeable lithium cell inside laptop batteries, e-bikes, torches and, in thousands, an electric car. Its name is its size: 18 mm across, 65.0 mm long. Protected versions add a small circuit at one end and are a couple of millimetres longer, which is why some torches take one and not the other.
The numbers
| Diameter | 18 mm · 0.71 in |
| Height | 65 mm · 2.56 in |
| Nominal voltage | 3.7 V |
| Chemistry | Lithium-ion |
| Other names | NCR18650, INR18650 |
Other cylindrical sizes
| Cell | Size | Voltage |
|---|---|---|
| AAA | 10.5 × 44.5 mm | 1.5 V |
| AA | 14.5 × 50.5 mm | 1.5 V |
| C | 26.2 × 50 mm | 1.5 V |
| D | 34.2 × 61.5 mm | 1.5 V |
| AAAA | 8.3 × 42.5 mm | 1.5 V |
| N | 12 × 30.2 mm | 1.5 V |
| A23 | 10.3 × 28.5 mm | 12 V |
| CR123A | 17 × 34.5 mm | 3 V |
| 21700 | 21 × 70 mm | 3.7 V |
Frequently asked questions
What size is a 18650 battery?
18 mm across and 65 mm long — 0.71 × 2.56 inches.
What voltage is a 18650?
3.7 V (Lithium-ion).
What do the numbers in 18650 mean?
They are the size. 18 is the diameter in millimetres and 650 is the length in tenths of a millimetre — so 18650 is 18 mm by 65 mm. The rule holds for every coin cell and every lithium-ion cylinder named this way.
Is the 18650 rechargeable?
Yes — this is a rechargeable cell and must be charged in a charger designed for lithium-ion.