One Swiss Knife in the exact shape of your life.

Sizes & Fits

Sizes & Fits, a small reckoner that computes in your browser and stores nothing. No account, no cloud, no telemetry.

Live · runs in your browser · no network

This is not a screenshot. It's the real tool, running right here: go on, put something in it.

Open the demo full-screen: /demos/sizes-fits.html

Forged into a knife, this tool ages with use: the blades you reach for wear soft, entries you tend keep their bloom, and the years travel with the file through every reforge.

You are a 42 at home, a 9 in one country, and something entirely mysterious in a third. Sizes & Fits converts sizes between systems — the shoes, the clothes, the fits that every region insists on numbering its own way — so you can order from abroad with reasonable hope. It computes the equivalent and keeps nothing, including any opinions about the sizing itself.

KindReckoner · computes, stores nothing
CategoryReckoners
Weight1
Manual:

Standing facts

In ten years

Sizes & Fits computes; it doesn't hoard. Open the file in 2036 and it will do the same arithmetic it does today, because the arithmetic is written into the file and nothing about it needs a server to agree.

If Offline.Ltd closes tomorrow, nothing on your machine notices. That isn't a marketing promise; it's simply what a file is.

Getting your data out

There is nothing locked in to get out: copy the numbers, or keep the file. Either way you owe no one a request form. No export queue, no "we'll e-mail you a link within 48 hours", no format that only one vendor can read.

Copy the file to a USB stick, a NAS, a folder your devices already sync. It runs on Windows, macOS, Linux, Android and iOS, online or off, because a browser is the only thing it ever needed.

Who else sees this

Nobody. Sizes & Fits works out its answer in your browser and forgets it the moment you close the tab: there is no store to breach, because nothing is stored. There is no account, no telemetry, no analytics, and no code in the file that opens a network connection, pull the cable and watch it carry on working. How privacy works across the Reckoners tools →

Questions people ask

01

How do I convert my shoe size between EU, UK, and US sizing?

Pick the system you know, enter your size, and read off the equivalents. It is a lookup done properly, without opening six contradictory conversion charts in six tabs.

02

Does the size converter work offline while I'm travelling?

Yes — it is one HTML file that runs in your browser with no connection needed, computes on the spot, and stores nothing. It works in the fitting room of a foreign department store, which is exactly where you will want it.

03

Will the converted size always fit perfectly?

The conversion gets you to the right number; whether the maker's idea of that number matches your foot is fashion's oldest joke. Treat it as an excellent starting point and read the reviews.

Go deeper on Sizes & Fits

More Reckoners

Fits your knife at weight 1. Nothing here is final, Knife follows Life. Reforging within your tier is free, forever. Add it, drop it, reforge it later; the file stays yours either way.

Share On X / Twitter → On LinkedIn → On Reddit →