Business SoftwareFree GST Calculator
Calculate GST, CGST, SGST and IGST from a base amount, or reverse-calculate the base amount and GST from a GST-inclusive total — no signup required.
Related tools
Use this GST calculation to create a business document with one of our other free tools.
Related reading
Understand the formulas and rules behind this calculation.
Manage GST invoicing alongside your business
Business Software connects your GST invoices, quotations and pricing history in one place, alongside CRM, sales and projects.
Create a free accountGST-exclusive vs. GST-inclusive
GST-exclusive adds GST on top of the amount you enter. GST-inclusive treats the amount you enter as the final, customer-facing total and works backward — mathematically correct reverse GST, not an approximation — to find the pre-tax base and the GST portion.
CGST, SGST and IGST
Intra-state sales split GST equally into CGST and SGST. Inter-state sales charge the full amount as IGST instead. This calculator lets you choose which applies to your transaction rather than guessing from any other detail.
Choosing a GST rate
The applicable GST rate depends on the goods or services involved and their classification. This calculator does not determine that for you — select the rate you already know applies (0%, 3%, 5%, 18% or 40%). Rates reflect GST 2.0, the slab structure effective 22 September 2025 under CBIC Notification No. 9/2025-Central Tax (Rate).
Important notes
This calculator covers standard GST slabs and straightforward base/GST/total math. It does not perform HSN/SAC lookup or compute GST Compensation Cess. This tool is provided for calculation convenience only — for tax filing or compliance decisions, consult a qualified tax professional.
Frequently asked questions
How do I calculate GST on an amount?
GST Amount = Base Amount × GST% ÷ 100. Add that to the base amount to get the final, GST-inclusive amount — for example, ₹1,000 at 18% GST adds ₹180 GST for a ₹1,180 final amount.
How do I calculate GST from a total (GST-inclusive) amount?
Back-solve the pre-tax base amount first: Base Amount = Inclusive Amount ÷ (1 + GST% ÷ 100). The GST amount is then Inclusive Amount − Base Amount. For example, a ₹1,180 inclusive amount at 18% GST back-solves to a ₹1,000 base and ₹180 GST.
What is the difference between GST-inclusive and GST-exclusive?
GST-exclusive means the amount you enter is the pre-tax price, and GST is added on top. GST-inclusive means the amount you enter already has GST built in, and this calculator works backward to show the pre-tax base amount and the GST portion.
What are CGST, SGST and IGST?
For an intra-state sale (buyer and seller in the same state), GST is split equally into CGST (Central GST) and SGST (State GST). For an inter-state sale, the full GST amount is instead charged as IGST (Integrated GST) — never all three at once.
Which GST rate should I use?
The applicable GST rate depends on the goods or services being sold and their classification, which this calculator does not determine — select the rate that applies to your transaction. Under GST 2.0 (effective 22 September 2025), the slabs are 0%, 5%, 18% and 40%, with a special 3% rate for gold, silver and precious stones.
Does this calculator account for GST Compensation Cess or HSN/SAC codes?
No — this is a straightforward rate/amount calculator. It does not determine HSN/SAC classification or compute Compensation Cess, both of which depend on product-specific rules beyond a generic calculator.