# Tip & Bill Split Calculator

> Tip, tax and who pays what: split a bill equally, by shares or by items, rounded up. Enter the bill, the tax rule (included as in most of Europe, or added at the till as in the US) and a tip as a percentage or an amount, before or after tax. Split equally, by shares or by what each person ordered, round each share up to 0.50 or 1, and get an exact who-pays-what table that adds up to the cent.

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://tipbillsplitcalculator.usefulweb.site/ (interactive tool at https://tipbillsplitcalculator.usefulweb.site/tool)
- JSON API: POST https://tipbillsplitcalculator.usefulweb.site/api/v1/calculate with a JSON object of inputs (schema: https://tipbillsplitcalculator.usefulweb.site/api/v1/tool)
- OpenAPI: https://tipbillsplitcalculator.usefulweb.site/openapi.json
- MCP (Streamable HTTP): https://tipbillsplitcalculator.usefulweb.site/mcp - tool `tip_bill_split_calculator`

## Inputs
- symbol (text): Currency symbol - Display only, e.g. €, $, £, CHF.
- billAmount (number, required): Bill amount - The amount printed on the bill (before tip).
- taxMode (select): Tax
- taxPercent (number): Tax rate
- tipMode (select): Tip given as
- tipPercent (number): Tip percentage
- tipAmount (number): Tip amount
- tipBase (select): Tip calculated on
- splitMode (select): Split
- people (integer): Number of people (equal split) - Used when the list of people below is empty.
- persons (table): People - Optional for an equal split. Shares: weight per person (default 1). Items: the bill amount of what each person ordered, in the same terms as the bill (with tax if tax is included); anything not assigned is shared equally.
- rounding (select): Rounding per person - Any rounding difference is added to (or taken from) the tip.

## Method
- Tax included (VAT): subtotal before tax = bill ÷ (1 + rate); tax = bill − subtotal. Tax added (sales tax): tax = bill × rate, rounded to the cent; bill total = bill + tax.
- Tip = tip % × tip base, where the base is the subtotal before tax or the total with tax (your choice), rounded to the cent; or a fixed tip amount.
- Weights: equal = 1 per person; shares = the share you enter; items = each person's ordered amount plus an equal part of anything not assigned to anyone.
- Bill, tax and tip are each split by weight with the largest-remainder method in whole cents, so the shares add up exactly to the totals.
- Rounding is applied per person to their exact total; the difference between what is collected and the exact total goes to the tip and is shown separately.