GST & Discount Calculator
Apply a discount and tax (GST/VAT) to a price, or work backwards from a tax-inclusive total to find the original base price and the exact tax amount — with an optional CGST + SGST split for invoicing.
GST & Discount Calculator
Apply a discount and tax (GST/VAT) to a price, or work backwards from a tax-inclusive total to find the original base price and the exact tax amount — with an optional CGST + SGST split for invoicing.
Invoice breakdown
How GST & Discount Calculator Works
The calculator supports two directions of GST calculation:
Discount is always applied to the original price first, and GST is then calculated on the discounted amount — matching how most retail and invoicing systems work. Tick "Split tax into CGST + SGST" to divide the tax amount evenly in two, as used on Indian GST invoices for intra-state sales.
Worked Example
Forward example: Price ₹1,000, discount 10%, GST 18%.
Base after discount = 1000 × 0.90 = ₹900. Tax = 900 × 0.18 = ₹162. Final price = ₹1,062.
Reverse example: A receipt shows a tax-inclusive total of ₹1,180 at 18% GST.
Base price = 1180 ÷ 1.18 = ₹1,000, meaning ₹180 of that total was GST.
Frequently Asked Questions
Can the GST calculator work backwards from a tax-inclusive price?
Yes. Switch to "Price includes tax" and enter the final amount to see the original base price and the exact tax amount it contains, with an optional CGST/SGST split.
Does the calculator apply the discount before or after tax?
Discount is applied to the original price first, and GST is then calculated on the discounted amount — matching how most retail and invoicing systems calculate the final payable price.
What is CGST and SGST?
Under India's GST system, tax on an intra-state sale is split evenly into Central GST (CGST) and State GST (SGST), each usually half the total GST rate. Tick the split option to see this breakdown for invoicing purposes.
Is this calculator specific to Indian GST, or can I use it for other countries' VAT?
The math works for any percentage-based sales tax or VAT system — just enter your local tax rate. The CGST/SGST split option is specific to India's GST structure and can simply be left unticked for other countries.