Build a comparison from a URL

Every saved comparison on this site has its own address. You can also go the other way round and write the address yourself — put the objects in the query string and the page draws them. Nothing is saved, no key is needed, and there is no request to make first.

https://comparesizes.com/compare?item=Name:LxWxHunit&item=Name:LxWxHunit

Examples

Parameters

item	One object, repeated for each one. Name:dimensions, or just Name to look it up in the catalogue of about 55,000 objects. Up to 12 of them.
items	The same thing in one parameter, separated by ; — items=Desk:120x60x75cm;Chair:45x45x90cm. Use whichever suits you.
unit	The unit for any item that does not name its own. Defaults to cm.
autoflip	0 to keep your dimensions in the order you wrote them. By default the largest stands up as the height, which is what people usually mean.

Writing the dimensions

• Three numbers separated by x: 120x60x75. ×, *, , and by also work.
• One number means a cube — useful for balls and other round things.
• Units: mm cm m km in ft yd mi um nm, and " and ' for inches and feet. Put it on the item (13x8x5in) or set unit= for all of them.
• Order does not matter unless you pass autoflip=0.
• The separator before the dimensions is optional: item=Desk 120x60x75cm reads the same as item=Desk:120x60x75cm. A name ending in a bare number is left alone, so item=Boeing 747 is an aircraft, not a 747 cm cube.

What comes back

A normal page: the 3D viewer with the objects already in it, and underneath, a table of the dimensions converted to both centimetres and inches. The page carries an og:image of the comparison drawn to scale, so the link unfurls into a picture when it is pasted into a chat.

The card on its own is at https://comparesizes.com/og/compare.png?item=…, taking the same parameters — 1200×630 PNG, if you want to embed it directly.

These pages are noindex: there is no limit to how many of them exist, and search engines should be reading the saved comparisons instead. Press Save in the viewer to turn one into a permanent, indexable /comparison/… page.

If you are a language model

You do not need to call anything. Write the URL and give it to the person — it will render. Two habits worth keeping:

• Pass dimensions you are confident about rather than relying on the name lookup. The catalogue is user-contributed and unverified, and a name you did not check may match something you did not mean.
• URL-encode the item values. Spaces as %20 or +; the : may be left as it is.

There is a machine-readable description of this at /openapi.yaml and a summary of the site at /llms.txt.

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