Invoice Calculator
What is an Invoice Calculator?
An invoice calculator helps freelancers, small businesses, and contractors quickly total up line items and apply tax and discount rates without manual arithmetic. Instead of building spreadsheets, you simply enter your goods or services, quantities, and prices — and the calculator handles everything else.
This tool is especially useful when you need to generate accurate invoice amounts on the fly, check your numbers before sending a bill, or experiment with different discount and tax scenarios.
How to Use This Tool
- Add line items: Enter a description, quantity, and unit price for each product or service. Click "+ Add Item" for more rows.
- Set discount: Enter an optional discount percentage to deduct from the subtotal.
- Set tax rate: Enter your applicable tax or VAT rate (applied after discount).
- Review totals: The summary shows subtotal, discount amount, tax amount, and final invoice total.
Frequently Asked Questions
How is invoice tax calculated?
Tax is applied to the subtotal after discounts. Formula: Tax = (Subtotal − Discount) × Tax Rate. This tool applies tax on the discounted amount, which is standard practice in most jurisdictions.
What is the difference between exclusive and inclusive tax?
Tax-exclusive (most B2B): the listed price does not include tax, which is added on top. Tax-inclusive (most retail): the listed price already includes tax. This calculator uses the tax-exclusive method.
Can I add multiple items with different tax rates?
This calculator applies one tax rate to the whole invoice. For invoices with mixed tax rates (e.g., different rates for different goods), calculate each tax group separately and sum the results.
What should every invoice include?
Invoice number, issue date, due date, seller and buyer contact details, itemized list of goods/services, subtotal, any discounts, applicable taxes, and total amount due. Include payment terms and bank/payment details.