Invoice Calculator
Line Items
$
$
%
%
Invoice Total$1,728.00
Subtotal$1,600.00
Discount$0.00
Tax$128.00
An invoice total is more than a single number: it is the sum of every line item, adjusted by any discount, with tax layered on top. This calculator lets you enter as many quantity-and-rate lines as you need, then applies a percentage discount to the subtotal and a tax rate to what remains, returning the subtotal, discount, tax, and final amount due.
Formula
total = (subtotal − subtotal × discount%) × (1 + tax%), subtotal = Σ qty × rate
- subtotal
- Sum of every line item (quantity × rate)
- discount%
- Discount applied to the subtotal
- tax%
- Sales or VAT rate applied after discount
How it works
- Add a line for each product or service with its quantity and unit rate; each line amount is quantity multiplied by rate and the subtotal is their sum.
- A discount percentage is taken off the subtotal first, producing the taxable amount.
- The tax rate is applied to that discounted amount, and the result is added back to give the invoice total.
Worked example
Ten design hours at $100 and five development hours at $120, with 8% tax and no discount.
- Subtotal = (10 × 100) + (5 × 120) = 1,000 + 600 = $1,600.
- Tax = 1,600 × 0.08 = $128.00.
- Total = 1,600 + 128 = $1,728.00.
Subtotal $1,600, tax $128, invoice total $1,728.00.
Frequently asked questions
- Is tax applied before or after the discount?
- This calculator applies the discount to the subtotal first, then taxes the discounted amount. That order matches how most jurisdictions tax the actual price the customer pays.
- Can I add as many line items as I need?
- Yes. Use the add button to insert more lines and the remove link to delete them. The subtotal updates live as you change any quantity or rate.
- How is rounding handled?
- Each line amount and the subtotal, discount, tax, and total are rounded to the nearest cent, so the figures match what you would print on a real invoice.