Invoice Total Calculator
The Invoice Total Calculator adds tax and applies any discount to a subtotal to give the final invoice amount. Enter the subtotal, the tax rate and any discount to see the tax, the discount and the grand total your customer needs to pay.
How an invoice total is built
An invoice total starts from the subtotal, the value of the goods or services before adjustments. From there you apply any discount, then add tax on the discounted amount, to reach the final figure the customer pays. The order matters: discount first, then tax.
The formula
Discounted subtotal = Subtotal − (Subtotal × Discount% ÷ 100). Tax = Discounted subtotal × Tax% ÷ 100. Grand total = Discounted subtotal + Tax.
A worked example
A subtotal of 1,000 with 18% tax and no discount gives tax of 180 and a grand total of 1,180. Add a 10% discount and the subtotal first drops to 900, the tax becomes 162, and the grand total is 1,062. Applying the discount before tax is the standard and usually the legally correct approach, because tax is charged on the actual amount payable.
Getting invoices right
Always show the subtotal, discount, tax and total as separate lines so the customer can see how the figure was reached, which also keeps your records clean for accounting. Use the correct tax rate for your region and product type, and state whether prices are inclusive or exclusive of tax to avoid disputes.
How to use
- Enter your details in the fields above. The Invoice Total Calculator accepts everyday values and checks them as you type.
- Press the action button (or just start typing for live tools) to run the calculation.
- Read your result, along with any supporting figures, in the clearly labelled result box.
- Use Copy result to grab the answer, Reset to start again, or Copy link to share this tool.
Why use this tool
Finance Wave built the Invoice Total Calculator to be genuinely useful: it validates your input so you never see a broken result, formats numbers for your region automatically, and stays readable in both light and dark mode. Because everything happens on your device, it is private by design and keeps working even without an internet connection once the page has loaded.