Invoice Total Calculator

The calculator works in this order:

1. Line amount = quantity × unit price, for each line.
2. Subtotal = the sum of the line amounts.
3. Discount = subtotal × discount rate, plus any additional discount in dollars. The discount can't be more than the subtotal.
4. Tax = (subtotal − discount) × tax rate.
5. Total due = subtotal − discount + tax.

The percentage part of step 3 and step 4 use the discount and sales tax formulas in the OpenStax Contemporary Mathematics textbook (section 6.2), with each rate written as a decimal (8.25% = 0.0825): discount = percent discount × original price, and sales tax = purchase price × tax rate. Adding a dollar discount and limiting the total discount to the subtotal are this calculator's own steps.

Each line amount, the percentage discount and the tax are rounded to the nearest cent. OpenStax gives the half-penny rule for sales tax ("round up for half a penny or more, but round down for less than half a penny"), and the calculator applies the same rule to each line amount, the percentage discount and the tax. The subtotal and the total add rounded amounts, so they're exact to the cent.

Worked example

These are the values the calculator starts with:

• Line 1: 2 × $150.00 = $300.00. Line 2: 1 × $75.00 = $75.00.
• Subtotal: $300.00 + $75.00 = $375.00.
• Discount: 10% of $375.00 = $37.50, with no additional discount.
• After discounts: $375.00 − $37.50 = $337.50.
• Tax at 8.25%: $337.50 × 0.0825 = $27.84375, which rounds down to $27.84.
• Total due: $337.50 + $27.84 = $365.34.

The 8.25% is only an example. Enter the rate that applies to your sale: whether a discount reduces the taxable amount, and which items are taxable, depends on the rules where the sale is taxed.

What you can enter

• Quantities up to 1,000,000 and unit prices up to $1,000,000,000, each with up to 4 decimal places, on up to 30 lines.
• Rates from 0% to 100%, with up to 4 decimal places. An empty rate or discount counts as 0.
• The additional discount, in dollars and cents.
• No negative numbers: enter a credit as a discount. A line with an empty quantity or unit price isn't counted.

To work out a discount on its own, use the discount calculator. To add or take out tax on a single amount, use the sales tax calculator, and to check what you keep after costs, the profit margin calculator. For what else to put on the invoice, see how to create a professional invoice.