GST Calculator
Add or remove GST at 5%, 12%, 18% or 28% (or any custom rate) and see the CGST/SGST split — also works as a VAT calculator.
About the GST Calculator
This GST calculator handles both directions of India's Goods and Services Tax maths. In "Add GST" mode, enter a base price and the calculator adds tax at 5%, 12%, 18%, 28% or any custom rate. In "Remove GST" mode, it works backwards from a GST-inclusive price to reveal the original amount and the tax hidden inside — the reverse GST calculation that trips up most people.
Adding GST is simple: gross = net × (1 + rate ÷ 100). Removing it requires division, not subtraction: net = gross ÷ (1 + rate ÷ 100). So an item billed at ₹1,180 with 18% GST has a base price of ₹1,000 and ₹180 tax — not ₹967.60 as a naive 18% deduction would suggest. The tool also splits the GST equally into CGST and SGST, as shown on intra-state invoices.
It is built for shopkeepers preparing invoices, freelancers quoting clients, accountants verifying bills and shoppers checking what they actually paid in tax. Because you can type any custom rate, it doubles as a VAT or sales-tax calculator for other countries.
How to Use the GST Calculator
- 1Enter the amount — either the base price or the GST-inclusive price.
- 2Choose "Add GST" for a base price or "Remove GST" for an inclusive price.
- 3Pick a GST slab (5%, 12%, 18%, 28%) or enter a custom rate.
- 4Read the net amount, GST amount, CGST/SGST split and gross total.
Frequently Asked Questions
How do I remove GST from a GST-inclusive price?
Divide the inclusive price by (1 + rate ÷ 100). For an 18% bill of ₹1,180: 1,180 ÷ 1.18 = ₹1,000 base, ₹180 GST. Simply deducting 18% from ₹1,180 gives the wrong answer because the 18% was charged on the base amount, not on the final price.
What are the GST slabs in India?
The main GST rates are 5% (essentials like packaged food and transport), 12% and 18% (most goods and services, including electronics and restaurants) and 28% (luxury and sin goods such as cars and aerated drinks). Some items are 0% or exempt, and special rates like 0.25% and 3% apply to gems and gold. Slabs are revised by the GST Council, so check current notifications.
What is the difference between CGST, SGST and IGST?
On sales within a state, GST is split equally between the Centre (CGST) and the state (SGST) — an 18% intra-state sale shows 9% + 9%. On inter-state sales, the full amount is charged as IGST to the Centre. The total tax you pay is the same either way.
Can I use this as a VAT calculator for other countries?
Yes. The add/remove maths is identical for VAT and sales tax anywhere — only the rate differs. Choose "Custom rate" and enter, say, 20% for UK VAT or 7% for Singapore-style GST. Ignore the CGST/SGST split, which is specific to Indian intra-state invoices.
Is GST charged on the discounted price or the original price?
GST is charged on the transaction value after discounts that are recorded on the invoice. So if a ₹2,000 item is sold with a 10% invoice discount, GST applies to ₹1,800. Post-sale discounts have different treatment under GST law, which matters mainly for registered businesses claiming input credit.