Invoice Calculator
Calculate invoice totals with line items, tax, discounts, and multi-currency conversion. Add up to 10 items, apply percentage or fixed discounts before tax, and convert totals between 7 currencies. Works with any currency.
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How to Use This Calculator
Tab "Create Invoice"
Add up to 10 line items with a description, quantity, and unit price. Set your tax rate and the calculator shows each line total, the subtotal, tax amount, and grand total in an itemized table.
Tab "With Discount"
Same line items as Tab 1, plus a discount applied before tax. Choose between a percentage discount or a fixed amount. The calculator shows the subtotal, discount amount, discounted subtotal, tax on the discounted amount, and the final total.
Tab "Multi-Currency"
Enter your invoice total in a base currency, an exchange rate, and a target currency. The result shows the converted total. Useful for international invoicing or quoting clients in their local currency.
The Formulas
Line Total = Quantity × Unit Price
Subtotal:
Subtotal = Sum of all Line Totals
Discount amount:
Discount = Subtotal × Discount% (or fixed amount)
Tax:
Tax = (Subtotal − Discount) × Tax Rate
Grand total:
Total = Subtotal − Discount + Tax
Currency conversion:
Converted Total = Invoice Total × Exchange Rate
All calculations are universal. No country-specific VAT, GST, or sales tax rules are applied. Results are estimates for planning purposes.
Worked Examples
Example 1 — Basic invoice: 3 items + 8% tax = $718.20
A freelance designer sends an invoice with three line items: website design ($500), logo design ($150), and SEO audit (1 hour at $15).
The subtotal of $665 plus 8% sales tax ($53.20) gives a grand total of $718.20.
Example 2 — Same invoice with 10% discount = $646.38
The same three items ($665 subtotal) with a 10% early-payment discount applied before tax.
The 10% discount reduces the subtotal to $598.50. Tax is calculated on the discounted amount: $598.50 × 8% = $47.88. Final total: $646.38.
Example 3 — USD to EUR conversion
An invoice totalling $1,000 USD needs to be quoted in euros for a European client.
At an exchange rate of 0.92, the $1,000 invoice converts to €920.00. Always confirm the live exchange rate with your bank or payment processor before sending the final invoice.
Understanding Invoice Calculations
What Is an Invoice?
An invoice is a commercial document that itemises a transaction between a seller and buyer. It lists goods or services provided, quantities, prices, applicable taxes, and the total amount due. Invoices serve as a legal record of the sale and a request for payment.
Tax Before or After Discount?
Standard accounting practice is to apply discounts before calculating tax. This means the customer pays tax only on the amount they actually owe after the discount. Applying tax before discount would result in the customer overpaying on sales tax, VAT, or GST.
Common Tax Rates by Region
Tax rates vary widely. US sales tax ranges from 0% to over 10% by state. EU VAT ranges from 17% (Luxembourg) to 27% (Hungary). UK VAT is 20%. India GST is 5%, 12%, 18%, or 28% depending on the category. Japan consumption tax is 10%. Brazil combined taxes can exceed 30%. Always verify with your local tax authority.
Multi-Currency Invoicing
When invoicing international clients, you can quote in their currency for convenience. Use the exchange rate from your bank or payment processor — not a web search result. Note that exchange rates fluctuate, so many businesses add a small buffer (1-3%) or specify that the rate is locked for a limited time (e.g., 7 days).
Best Practices
Include a unique invoice number, issue date, payment terms (e.g., Net 30), your business details, and the client's details. Clearly separate the subtotal, any discounts, tax, and total. For international invoices, specify the currency and exchange rate used.