Due to the variation in blade types that can be fitted, pocket knife lengths and weights are measured excluding the blade, which is measured separately (see What pocket knife blade sizes are available?)
Folding pocket knives
Folding pocket knives measure between the shortest at 110mm (4.3in), and the longest at 235mm (9.3in).
The lightest folding pocket knives, some of which are small enough to fit on a keychain, weigh just 40g (1.4oz), while the heaviest can weigh up to 250g (8.8oz).
Retractable pocket knives
The shortest retractable pocket knives measure 84mm (3.3in), 26mm shorter than the shortest folding pocket knife, while the longest can measure up to 222mm (8.7in).
Retractable pocket knives tend to be shorter than folding knives because the handle is built in one section, with most parts internal, and does not require additional space for a pivot, bolster, or external blade liner.
However, there is little difference between the weight range of folding and retractable pocket knives. The lightest retractable pocket knife weighs 50g (1.8oz), 10g more than the lightest folding model, while the heaviest weighs 250g (8.8oz), exactly the same as the heaviest folding model.
Fold and retract pocket knives
The shortest fold and retract pocket knife measures 150mm (6in), while the longest measures 254mm (10in).
Fold and retract pocket knives are the heaviest models available; this is because of the need to incorporate both the external pivot, bolster and liner of a folding pocket knife, and the more complex internal mechanism of a retractable pocket knife.
The lightest model of fold and retract pocket knife weighs 60g (2.1oz), 10g heavier than the lightest retractable model and 20g heavier than the lightest folding model, while the heaviest weighs 250g (8.8oz), the same as the heaviest folding and retractable models.
