Invoice Calculator

Calculate invoice totals with line items, tax, and discounts. Add or remove rows as needed.

Last reviewed: June 2026
Built and maintained by · Last updated June 2026
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Subtotal
$0.00
Discount Amount
$0.00
Tax Amount
$0.00
Grand Total
$0.00
Important Disclaimer: This invoice calculator is a browser-based arithmetic tool for estimating totals from line items, discounts, and tax rates. It does not create a legal invoice template, determine whether sales tax applies, track payment status, or replace your accounting records.

What this Invoice Calculator does

This page calculates an invoice total from editable line items. Each row has a description, quantity, unit price, and line total. Below the rows, you can apply a percentage discount and a percentage tax rate. The calculator then shows the subtotal, discount amount, tax amount, and grand total.

The tool is intentionally simple. It does not collect client names, invoice numbers, dates, due dates, terms, payment links, or templates. Use the print button if you want a browser-printable calculation, and use the share link if you want to reopen the same line items and rates later.

Invoice math used

Each line total is quantity x unit price. The subtotal is the sum of all line totals. The discount is calculated from the subtotal. Tax is calculated on the discounted amount, not on the original subtotal. The final formula is grand total = subtotal - discount + tax on discounted subtotal.

Default example

The default rows are Website Design at $2,500, Logo Design at $800, and Hosting (Annual) at $120. With no discount and no tax, the subtotal and grand total are both $3,420.00.

If you apply a 10% discount, the discount amount is $342.00 and the taxable amount becomes $3,078.00. If the tax rate is 8.25%, the tax amount is $253.94 and the grand total is $3,331.94. This makes the order of operations clear: discount first, tax second.

When this is useful

  • Freelance estimates: compare fixed-fee tasks, hourly blocks, and reimbursable costs before sending a formal invoice.
  • Small purchase orders: total several parts or services with a known tax rate.
  • Discount checks: see how a percentage discount changes the taxable amount and final price.
  • Client conversations: share a calculation link while scope and quantities are still being discussed.

Common mistakes

  • Putting tax into the unit price and again into the tax field: that double counts tax.
  • Using a discount rate for a flat discount: this calculator accepts a percentage discount only. Convert a flat discount to a percentage or subtract it outside the tool.
  • Assuming taxability: services, products, shipping, discounts, and exemptions are treated differently by jurisdiction.
  • Using the printout as a complete invoice: add invoice number, business details, client details, payment terms, and required tax language in your accounting or invoicing system.
  • Forgetting quantity: three hours at $90 should be quantity 3 and unit price 90, not quantity 1 and unit price 90.

Practical workflow

Use this calculator to confirm the arithmetic before you prepare the official document. After the amount is settled, copy the final numbers into your bookkeeping system, invoice software, contract, or spreadsheet. Keep the share link for the estimate, but keep formal records in the system you use for taxes and payment tracking.

Frequently Asked Questions

It uses line description, quantity, unit price, discount percentage, and tax percentage. It does not have client, due-date, payment, or template fields.
Tax is calculated after the percentage discount. The taxable amount is subtotal minus discount.
Yes. Use Add Line Item for another row, the remove button for one row, or Clear All to start with an empty line-item list.
The discount input is percentage-based. For a fixed dollar discount, convert it to a percentage of the subtotal or subtract it in your final invoicing system.
No. It calculates totals. A complete invoice usually needs business details, client details, dates, invoice number, payment terms, and any required tax or compliance language.