# Price Per Everything

> Compare products by price per gram, use, serving, hour or year of life. Enter two or more products with their price and quantity (grams, uses, servings, hours or years). Price Per Everything normalises them to the same basis, accounts for waste, and ranks them from cheapest to most expensive per unit.

Part of usefulweb.site (https://usefulweb.site/). Results are deterministic calculations from the inputs and the listed assumptions; the API returns exactly what the web page shows.

## Use it
- Human interface: https://pricepereverything.usefulweb.site/ (interactive tool at https://pricepereverything.usefulweb.site/tool)
- JSON API: POST https://pricepereverything.usefulweb.site/api/v1/calculate with a JSON object of inputs (schema: https://pricepereverything.usefulweb.site/api/v1/tool)
- OpenAPI: https://pricepereverything.usefulweb.site/openapi.json
- MCP (Streamable HTTP): https://pricepereverything.usefulweb.site/mcp - tool `price_per_everything`

## Inputs
- basis (select): Compare by
- currency (text): Currency - Shown in results only; no conversion is performed.
- products (table, required): Products - Quantity is in the chosen basis (e.g. 500 for 500 g, 30 for 30 uses). Waste % reduces the usable quantity.

## Method
- Usable quantity = quantity × (1 − waste %).
- Price per unit = price ÷ usable quantity, unrounded internally; displayed with 4 significant digits.
- Products are ranked by price per unit; ties keep input order.