diff --git a/README.md b/README.md
index 903cfa4..c493fb7 100644
--- a/README.md
+++ b/README.md
@@ -9,6 +9,7 @@ You can also get the [raw data](https://heisse-preise.io/api/index). The raw dat
 * `price`: the current price in €.
 * `priceHistory`: an array of `{ date: "yyyy-mm-dd", price: number }` objects, sorted in descending order of date.
 * `unit`: unit the product is sold at. May be undefined.
+* `quantity`: quantity the product is sold at for the given price
 * `bio`: whether this product is classified as organic/"Bio"
 
 The project consists of a trivial NodeJS Express server responsible for fetching the product data, massaging it, and serving it to the front end (see `index.js`). The front end is a least-effort vanilla HTML/JS search form (see sources in `site/`).