# item.guide
Side-by-Side Comparison Cylindrical Cells

18650 vs. 21700

Comparing 2 standards across 4 specifications. 4 key differences identified.

Comparing:
18650
21700
18650 →

An 18650 Li-ion cell measures 18.6mm in diameter and 65.2mm in length. It operates at 3.6V/3.7V nominal, charges up to 4.2V max, and has a discharge cutoff of 2.5V with capacities between 2200 and 3500 mAh.

View full 18650 spec sheet →
21700 →

A 21700 Li-ion cell measures 21.1mm in diameter and 70.4mm in length. Offering 4000 to 5000 mAh capacity at 3.6V nominal, it provides up to 50% more energy density than an 18650 cell.

View full 21700 spec sheet →

Specification Comparison Table

4 Parameters
Parameter / Spec
18650
21700
Diameter
18.60 mm 21.10 mm
Overall Length
65.20 mm 70.40 mm
Nominal Operating Voltage
3.60 / 3.70 V —
Nominal Capacity
— 4000–5000 mAh

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