18650 vs 21700 vs 26650
Cylindrical lithium cells are named after their size in millimetres. The three most common are the 18650, 21700 and 26650. Here is how they compare and where each one fits.
Quick comparison
- 18650 – approx 18 x 65 mm. Typical capacity 2000–3500 mAh. The most widely used size: torches, vapes, laptops, power tools, e-bikes and DIY packs.
- 21700 – approx 21 x 70 mm. Typical capacity 3000–5000 mAh. More capacity and often higher drain than an 18650; used in newer torches, high-power vapes, e-bikes and EV packs.
- 26650 – approx 26 x 65 mm. Typical capacity 3500–5500 mAh. A fatter cell for high-capacity torches and solar/DIY packs.
Which should you buy?
Always match the size your device is designed for – a 21700 will not fit an 18650 tube and vice versa. If you are building a pack or buying a new device and have a choice, 21700 cells generally offer the best balance of capacity and power today, while 18650 remains the cheapest and most universal.
Discharge still matters
Size does not tell you how hard a cell can push. A high-capacity cell may be low-drain. Always check the continuous discharge rating (A) against your device – see our how to choose guide.
Browse genuine 18650, 21700 and 26650 cells at 18650.com.au – shipped Australia-wide with local pickup in Melbourne.