Reverse GST Calculator – Remove or Add GST Instantly in 3 Easy Steps
GST Calculator
Use this reverse GST calculator to get exact tax amounts by adding GST to a base price or removing it from a total.
Use this free reverse GST calculator to find the price before tax from a GST-inclusive total, or switch to forward mode to add GST to a base price. Enter the amount, pick a rate such as 5%, 18% or 40%, and see the net price, GST amount and gross total instantly.
Quick answer
To remove GST from a total, divide by (1 + GST rate ÷ 100). The GST amount is the total minus that base price, or total × rate ÷ (100 + rate). For example, ₹1,180 including 18% GST has a base price of ₹1,000 and GST of ₹180. To add GST, multiply the base price by (1 + rate ÷ 100).
Table of Contents
Shop bills, supplier quotes and online prices usually show the final amount with tax already included. To claim input tax credit, check an invoice or set your own prices, you need to split that amount into the base price and the tax.
This reverse GST calculator does the split in one click. It works with any GST or VAT rate, so you can use it in India, Australia, New Zealand, Singapore, Canada and other countries.
What Is Reverse GST Calculation?
A reverse GST calculation works backwards from a tax-inclusive price to find how much of it is tax. A common mistake is to take 18% of the total. That gives the wrong answer because the GST was calculated on the smaller base price, not on the total.
For ₹1,180, 18% of the total is ₹212.40, but the real GST is ₹180. The reverse formula avoids that error.
Reverse GST Formula
- Base price = GST-inclusive total ÷ (1 + GST rate ÷ 100)
- GST amount = total − base price
- Shortcut: GST amount = total × rate ÷ (100 + rate)
Forward GST Formula
- GST amount = base price × GST rate ÷ 100
- Total price = base price + GST amount = base price × (1 + rate ÷ 100)
Reverse GST Examples
| Total (incl. GST) | GST rate | Base price | GST amount |
|---|---|---|---|
| 1,050 | 5% | 1,000.00 | 50.00 |
| 1,180 | 18% | 1,000.00 | 180.00 |
| 1,400 | 40% | 1,000.00 | 400.00 |
| 5,000 | 18% | 4,237.29 | 762.71 |
| 110 | 10% | 100.00 | 10.00 |
| 115 | 15% | 100.00 | 15.00 |
How to Use the Reverse GST Calculator
Step 1: Enter the Total and GST Rate
Keep Remove GST (Reverse) selected. Type the total amount including tax, then enter the GST rate or tap one of the quick buttons for 5%, 10%, 15%, 18% or 40%.
Step 2: Read the Base Price and GST Amount
Press Calculate GST. For a total of 1,180 at 18%, the calculator shows a net price of 1,000.00 and GST of 180.00, along with the formula it used so you can check it.
Step 3: Add GST to a Base Price
Switch to Add GST (Forward) when you start from a price before tax. A base price of 2,500 at 5% GST adds 125.00, for a total of 2,625.00.
GST Rates in India and Other Countries
Since the GST 2.0 reform of September 2025, India mainly uses two GST rates, 5% and 18%, with a 40% rate for luxury and sin goods, while some essentials are exempt. Other countries use a single main rate:
| Country | Standard GST rate |
|---|---|
| India | 5% and 18% (40% for luxury and sin goods) |
| Australia | 10% |
| New Zealand | 15% |
| Singapore | 9% |
| Canada | 5% federal GST (HST up to 15% in some provinces) |
Rates change from time to time and some products have special rates, so check the official rate for your item before filing.
CGST, SGST and IGST in India
For a sale within one state, the GST is split equally between central GST (CGST) and state GST (SGST). An 18% rate becomes 9% CGST plus 9% SGST, so ₹180 of GST on a ₹1,000 base is ₹90 + ₹90. For sales between states, the full rate is charged as integrated GST (IGST).
Working out tax on freelance work? Try the Freelancer Invoice Tax Calculator. For profit after a discount, use the Markdown Calculator.
Frequently Asked Questions
How do I calculate GST from a total amount?
Divide the total by (1 + rate ÷ 100) to get the base price, then subtract it from the total. For 18% GST, ₹1,180 ÷ 1.18 = ₹1,000, so the GST is ₹180.
Why can’t I just take 18% of the total?
Because GST is charged on the base price, not on the total. Taking 18% of a tax-inclusive total overstates the tax.
What are the current GST rates in India?
After GST 2.0, the main rates are 5% and 18%, with a 40% rate on luxury and sin goods and some items exempt.
Can I use this calculator for VAT?
Yes. VAT works the same way. Enter your VAT rate, such as 20% in the UK, and use reverse mode to remove it from a total.
How do I split GST into CGST and SGST?
For sales within the same state, divide the GST amount by two. Half is CGST and half is SGST.
Is my data saved?
No. The reverse GST calculator runs in your browser and nothing is stored or sent.