T. rex vs Modern London Double-Decker Bus: longer by how much?
A T. rex measures 12 m (39.4 ft) end to end, and a modern London double-decker bus measures 10.9 m (35.8 ft) end to end. That puts a T. rex at 1.10 times the length of a modern London double-decker bus: 1.1 m (3.61 ft) of difference, 10%. Put the other way round, a modern London double-decker bus covers 91% of a T. rex on the axis both are judged on. A T. rex and a modern London double-decker bus are both written in tens of metres, and the 10% between them is the whole of the difference.
| Object | Real size | Axis measured | What the figure covers |
|---|---|---|---|
| T. rex | 12 m 39.4 ft |
Length | Average Adult |
| Modern London Double-Decker Bus | 10.9 m 35.8 ft |
Length | Modern Low-Floor Type |
Both figures, T. rex and Modern London Double-Decker Bus, 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
A T. rex sits in the range with no handy yardstick: too big to hold against anything you have carried, too small to need a horizon, so it and a modern London double-decker bus end up filed under the same vague heading of very large. A gap of 10% is invisible without a shared baseline: on the ground line above, a modern London double-decker bus stops 1.1 m (3.61 ft) short of a T. rex.
What each figure covers
T. rex. T. rex is quoted nose to tail. Specimens differ by metres, and the largest known individual is considerably longer than the average used here.
Modern London Double-Decker Bus. The modern low-floor bus runs about half as long again as the Routemaster it replaced, which is the shape most people still picture when they hear double-decker.
A T. rex and a modern London double-decker bus 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, T. rex at 12 m sits within a tenth of Whale Shark at 12.1 m, X-wing Starfighter at 12.5 m and Hubble Space Telescope at 13.2 m. Modern London Double-Decker Bus at 10.9 m has Quetzalcoatlus at 10.5 m, Whale Shark at 12.1 m and X-wing Starfighter at 12.5 m for company, within a quarter. Swapping any of those in for a T. rex would move its ratio to a modern London double-decker bus by less than 10%.