GST Calculator
Add GST to a base amount or work backward from a GST-inclusive price — with an instant CGST/SGST or IGST split.
This calculator gives an indicative estimate based on standard rates and slabs. It isn't a substitute for professional advice — talk to a senior CA for a computation specific to your situation.
How GST calculation works
GST is charged as a percentage of the value of a supply. When you're quoting a price and need to add GST, multiply the base amount by the rate and add it on top. When you have a GST-inclusive amount and need to find the base value — common when reverse-calculating from a total invoice value — divide the total by (1 + rate ÷ 100).
CGST, SGST and IGST
A sale within the same state splits GST equally between CGST (central government) and SGST (state government). A sale across state lines is charged as IGST instead, collected centrally and apportioned to the destination state. Either way, the total tax rate you pay is identical — only the split changes.
Using this for real invoices
This calculator is a quick reference for quotes and estimates. For actual GST registration or monthly return filing, our GST registration and GST monthly return filing services handle the numbers end-to-end, reviewed by a senior CA.
Frequently asked questions
How do I calculate GST on an amount?▾
To add GST, multiply the base amount by the GST rate and add it to the base — for example, ₹10,000 at 18% GST is ₹10,000 + ₹1,800 = ₹11,800. To find the base amount from a GST-inclusive price, divide the total by (1 + rate/100).
What's the difference between CGST, SGST and IGST?▾
For a sale within the same state, GST is split equally into CGST (central) and SGST (state). For a sale across state lines, the full amount is charged as IGST instead. The total tax you pay is the same either way.
Which GST rate should I use?▾
GST rates are notified by HSN/SAC code, not by product name. Most goods and services now fall under 5% or 18% following the rate rationalisation, with a special 40% rate for sin and luxury goods — check the official rate finder for your specific product.
Is this calculator accurate for GST returns filing?▾
This calculator gives an instant estimate for invoicing and quotes. For actual GST return filing, use our GST monthly return filing service so a senior CA reviews the numbers before submission.
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