How big is a London black cab compared to a leatherback turtle?
A London black cab measures 4.6 m (15.1 ft) end to end, and a leatherback turtle measures 2.35 m (7.71 ft) end to end. A leatherback turtle would have to grow by 96% to match a London black cab, which is 1.96 times its length. Put the other way round, a leatherback turtle covers 51% of a London black cab on the axis both are judged on. A London black cab and a leatherback turtle are both written in single metres, and the 96% between them is the whole of the difference.
| Object | Real size | Axis measured | What the figure covers |
|---|---|---|---|
| London Black Cab | 4.6 m 15.1 ft |
Length | Whole body or structure, end to end |
| Leatherback Turtle | 2.35 m 7.71 ft |
Length | Average Female, Swimming Pose |
Both figures, London Black Cab and Leatherback Turtle, come from the Size It Up measurement set, one real-world size and one measured axis per object, last checked in September 2026; outline provenance is listed on the sources page.
Why this one is hard to judge by eye
Both shapes fit in a single glance here, which is exactly why the 96% between a London black cab and a leatherback turtle slips past: at this size the eye compares whole outlines, and the figures above compare one axis.
What each figure covers
London Black Cab. The cab is measured bumper to bumper. Its turning circle, not its length, is the specification London has always been strict about.
Leatherback Turtle. Leatherbacks are measured nose to tail in the swimming pose. They are the largest turtle alive and the only one without a hard shell of bone.
A London black cab and a leatherback turtle are both quoted as a length, which is what makes the ratio above a like-for-like figure.
What else is about that size?
Measured the same way, London Black Cab at 4.6 m sits within a tenth of Land Rover Defender 110 at 4.6 m, Kyogre at 4.5 m and Saltwater Crocodile at 4.5 m. Leatherback Turtle at 2.35 m has Bull Shark at 2.4 m, Harley Davidson at 2.4 m and Horse at 2.4 m for company, within a tenth. Swapping any of those in for a London black cab would move its ratio to a leatherback turtle by less than 10%.