What is a GST Calculator?
A GST calculator adds GST to a net price or removes GST from a price that already includes it. It shows the tax amount and how it splits into CGST and SGST for sales within a state, or IGST for sales between states.
GST Calculator works in both directions: it adds GST to a net price for an invoice, or strips GST out of a price that already includes it so you can see the base value and the tax inside it.
How does the GST Calculator work?
To add GST to a net price, multiply the price by the GST rate.
GST = Net amount × rate/100
Total = Net amount + GSTWorked example using the starting values on this page:
- Amount
- ₹10,000
- GST rate
- 18.0%
- Amount entered is
- Before GST
- Supply
- Within state
- Net amount
- ₹10,000
- GST amount
- ₹1,800
- Total amount
- ₹11,800
- CGST (9.00%)
- ₹900
How to use the GST Calculator
- Enter the amount (anywhere from ₹1 to ₹10,00,00,000). Type it in the box or drag the slider.
- Enter the gst rate (anywhere from 0.0% to 40.0%). Type it in the box or drag the slider.
- Choose amount entered is: Before GST or Including GST.
- Choose supply: Within state or Other state.
- Read the gst amount at the top of the results, then check the breakdown below it.
- Change one input at a time to compare scenarios, and note how much each change moves the result.
Benefits of using the GST Calculator
- Applies the current rules step by step, so you can see how the final figure is reached.
- Lets you test different amounts and options before you file, sign an offer or raise an invoice.
- Shows the breakdown, not just a single number, which makes it easier to check payslips, invoices or Form 16.
- Free, instant and private: nothing you enter is stored.
Mistakes to avoid with the GST Calculator
The common mistake is taking 18% of a GST-inclusive price, which overstates the tax. Divide by 1.18 instead.
Read the net amount, GST and total together, and check whether the supply is within a state (CGST + SGST) or between states (IGST).
Helpful checks before using the result
These checks make a gst more useful in practice.
- Start with a realistic base case rather than the first value that fits the range slider.
- Change one major assumption at a time so the effect stays easy to interpret.
- Use the result to compare scenarios, not as a final provider quote or guaranteed outcome.
- Verify rates, rules, and product terms separately before acting on the estimate.
How GST is split on an invoice
The total tax is the same; what changes is who collects it.
- Within the same state (intra-state supply), GST is split into equal halves: CGST to the centre and SGST to the state.
- Between states (inter-state supply) and on imports, the full rate is charged as IGST.
- Following the GST rate rationalisation of September 2025, most goods and services fall under 5% or 18%, with 40% on a short list of luxury and sin goods and special rates such as 3% on gold.
Two common GST calculations
Most people need one of these two directions.
Adding GST
For a ₹10,000 service at 18%, GST is ₹1,800 and the invoice total is ₹11,800.
Removing GST
For a ₹11,800 price that includes 18% GST, the base price is ₹10,000 and the GST inside it is ₹1,800.
Checking an invoice
Enter the taxable value and rate shown on the bill and compare the GST with what was charged.
GST Calculator FAQs
How do I calculate GST on an amount?
Multiply the net amount by the GST rate and divide by 100. At 18%, GST on ₹10,000 is ₹1,800, so the total is ₹11,800.
How do I remove GST from a price that already includes it?
Divide the price by (1 + rate ÷ 100). For ₹11,800 at 18%: 11,800 ÷ 1.18 = ₹10,000 before GST, so the GST inside the price is ₹1,800.
What is the difference between CGST, SGST and IGST?
For a sale within one state, GST is split equally into CGST (central) and SGST (state). For a sale from one state to another, the whole rate is IGST.
Which GST rate applies to my product?
It depends on the HSN or SAC code of the goods or service. Check the current GST rate notification or your accountant; this calculator works with any rate you enter.
