No size tag? One measurement tells you the size. Here's the chart we use

Simple rules that turn a chest measurement into a size: a coat is twice its chest measurement, a shirt measuring 22 inches across is a Medium, 24 a Large, 26 an XL. Fewer returns for wrong sizes.

Paul from Beartooth Bargains · Oct 14, 2026

What happened in our store

No more 42R coats that were really 40L

Time to set up: Minutes, once the rules are written down
Cost: Free
Tools: Claude
Sells on: eBay, Poshmark, Depop

The problem

Vintage and workwear often has no size tag, or a tag that lies. Guessing wrong means a return.

The workflow

The agent reads the pit-to-pit from the labelled measurement photo.
Coats and jackets: size is twice the pit-to-pit, and the listing says Regular length unless the sleeve says otherwise. A 20-inch pit-to-pit is a 40.
Shirts: 22 inches is Medium, 24 is Large, 26 is XL, with the in-between values rounded toward the smaller size.
The estimate is shown on the review page with the measurement it came from, so the seller can see "40 from a 20-inch chest" and fix it if the garment runs big.
Every correction the seller makes becomes a saved test case, and the rules are re-scored against all of them before they change.

Why rules instead of letting the model guess

Model guesses drift. A written rule gives the same answer every time and can be fixed in one place when it is wrong.

For your store

Our honest estimate from running this. Your store and numbers will differ.

What you need: A ruler or tape measure and the size rules from this page, saved in a note you can paste into your AI chat.
First try takes: Ten minutes to write the rules for what you sell.
First step tonight: Copy the coat and shirt rules into a note. On your next untagged item, measure pit to pit and check the size against the rule before you list it.
After a week: Untagged items listed with a size you can defend, and fewer "runs small" messages. If your brands run big, adjust the shirt numbers, then keep using the same rule every time.

Tools in this one

Claude Anthropic's assistant and agent. Runs the lister, auditor and pack list in the Beartooth store.