21700 battery size
21 × 70 mm
3.7 V · Lithium-ion · Cylindrical · also sold as INR21700
About the 21700
The larger rechargeable lithium cell that has largely replaced the 18650 in new designs: 21 mm by 70.0 mm, about 50% more volume and correspondingly more capacity. The naming rule is the same one, which is the easiest way to remember either.
The numbers
| Diameter | 21 mm · 0.83 in |
| Height | 70 mm · 2.76 in |
| Nominal voltage | 3.7 V |
| Chemistry | Lithium-ion |
| Other names | INR21700 |
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 |
| 18650 | 18 × 65 mm | 3.7 V |
Frequently asked questions
What size is a 21700 battery?
21 mm across and 70 mm long — 0.83 × 2.76 inches.
What voltage is a 21700?
3.7 V (Lithium-ion).
What do the numbers in 21700 mean?
They are the size. 21 is the diameter in millimetres and 700 is the length in tenths of a millimetre — so 21700 is 21 mm by 70 mm. The rule holds for every coin cell and every lithium-ion cylinder named this way.
Is the 21700 rechargeable?
Yes — this is a rechargeable cell and must be charged in a charger designed for lithium-ion.