Invoice Calculator

Adds up any number of line items into a subtotal, applies one shared percentage discount, then calculates tax on the discounted amount and shows the final total due.

Enter a quantity and unit price for each line item, click "Add line item" for as many rows as you need, then set an overall discount percentage and tax rate. Every field updates the totals immediately.

Two line items — 3 units at 50 each and 1 unit at 200 — give a subtotal of 350. A 10% discount brings that to 315, and a 20% tax on the discounted amount adds 63, for a total due of 378.

The discount is applied to the subtotal first, and tax is calculated on the already-discounted amount, not the original subtotal — this matches how most invoicing software computes tax-after-discount.

Subtotal is the sum of quantity × unit price across all rows. Discounted amount equals subtotal × (1 − discount / 100). Total due equals the discounted amount × (1 + tax / 100).

This tool only calculates totals — it doesn't save, number, send or export an invoice, and it doesn't handle per-line tax rates, rounding rules, multiple currencies or partial payments.

All line items and totals are calculated locally in your browser; nothing you enter is uploaded or stored.