How to use Invoice Total Calculator
This tool checks the arithmetic for a single item: multiply quantity by price, subtract the percentage discount, then apply the tax rate to the discounted amount. Fractional quantities are supported for items sold by weight or length.
It does not create an official invoice, verify an applicable tax rate or determine whether a discount changes the taxable value under current rules. Shipping, multiple tax rates and rounding policies require separate treatment.
The formula
A worked example
Unit price before tax (₹): 1000 · Quantity: 3 · Discount (%): 10 · Tax rate (%): 18
Invoice total: ₹3,186.00
One line item; discount before tax. This is an arithmetic estimate, not a compliant GST invoice or tax filing tool.
Questions about this calculation
Is the discount applied before tax?
Yes. The entered tax rate is applied to the discounted subtotal.
Can I issue this as an official invoice?
No. It is a calculation only and does not contain the required invoice details or regulatory checks.
Formula checks: 2026-10-08. Assumptions & corrections.