Length Compare

[Please note first] This app cannot measure anything. It uses no camera and no motion sensor. You type in a length you already know, and it shows you what is about that size. Areas, volumes and travel distances are out of scope. ────────── ⇕ Length Compare — how long is that, really? "Tokyo Skytree is 634 metres" does not tell you much. In people, that is 371 adults. A 30 cm rule comes to exactly 15 one-yen coins laid side by side. Enter one length and compare it against 26 everyday things, from cedar pollen to the Seikan Tunnel. ■ Two ways to use it ▪ About this long — the things closest to your length, shortest first ▪ How many — how many of each thing your length comes to The same 26 entries are used both ways: searched by nearness with one switch at the top, divided with the other. "What is 1.71 m long?" and "how many people high is Tokyo Skytree?" are the same two taps. ■ Twenty-six things Cedar pollen, a human hair, a sheet of copier paper, a sesame seed, a one-yen coin, a credit card, a 30 cm ruler, a bowling pin, a newborn baby, a guitar, an adult man, a door, a giraffe, a utility pole, the Great Buddha of Nara, a blue whale, a 10-storey building, the Statue of Liberty, a Boeing 747-400, Tokyo Tower, a 16-car Shinkansen, Tokyo Skytree, the Burj Khalifa, Mount Fuji, Mount Everest and the Seikan Tunnel. Tap any row to load its length. ■ Height, length and thickness on one line A human hair is 0.08 mm across; Tokyo Skytree is 634 m high. Three different words for one quantity, with about nine orders of magnitude between the two ends of the list. ■ Exact figures and ranges are kept apart A one-yen coin is exactly 20.0 mm across under the Currency Act. A credit card is exactly 85.60 by 53.98 mm under ISO/IEC 7810. A bowling pin is exactly 15 inches, or 381 mm. So 30 cm comes to exactly 15 one-yen coins. Living things and street furniture vary with conditions, so ten of the 26 entries carry a range as well: 3.9 to 5.5 m for a giraffe, 8 to 14 m for a utility pole. The range is shown only for reading; the comparison always uses the single typical figure. ■ Readable at every scale The same screen shows 0.035 mm and 53.9 km. Each row picks its own unit so the number stays readable. mm → cm → m → km Figures are rounded to three digits: Mount Everest reads 8.85 km and the Seikan Tunnel 53.9 km. Nothing below three digits changes how two things compare. ■ Good for ▪ Making sense of a figure in metres from the news ▪ Explaining length to a child ▪ Putting the size of something you are buying into everyday terms ▪ Any moment you see a number and wonder whether it is long ■ Things worth knowing (included in the app) ▪ A one-yen coin is exactly 20.0 mm across, so 30 cm is 15 of them ▪ A bowling pin is exactly 15 inches, and the 1.27 you see is the inch itself ▪ A credit card is exactly 85.60 by 53.98 mm under ISO/IEC 7810 ▪ Everest had no single agreed height until the joint announcement of 2020 ▪ A range under a name is not a margin of error; it is how much it varies ▪ Figures are shown to three digits, and the underlying values are finer ■ How the app is built ▪ A single screen. No settings page; two switches at the top change the list ▪ Your last five entries are kept and can be tapped to restore ▪ Japanese and English, following your device language ▪ No account needed. The comparison runs on your device and your figures are never sent anywhere ────────── Note: all lengths are typical guides and vary with type and conditions. Only the items fixed by law or by a standard — the one-yen coin, the credit card and the bowling pin — are exact. This app cannot measure anything, and areas, volumes and travel distances are out of scope.