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GST Calculator India: Add or Remove GST

Use this GST calculator for India to add GST to a price or remove it from a GST-inclusive amount, in rupees. Enter the rate from your invoice to see the base amount, the GST and the CGST + SGST or IGST split.

Enter amount and GST details

Calculation mode

Greater than 0, up to ₹100 crore, with at most 2 decimal places.

GST rate

Pick the rate shown on your invoice or the official GST notification, or choose Other rate to type any rate. This calculator does not look up rates or know which rate applies to an item.

Transaction type

Enter an amount to see the base amount, GST split and final amount.

Assumptions & calculation breakdown

Formulas used

  • Add GST: GST = base × rate / 100; final amount = base + GST.
  • Remove GST: base = amount × 100 / (100 + rate); GST = amount - base.
  • Intra-state: CGST and SGST are each half of the GST. Inter-state: IGST is the whole GST.

Assumptions

  • The GST rate is the one you select or type. GST rates and slab structures change; use the rate shown on your invoice or the official GST notification. This calculator does not know which rate applies to a given item.
  • Cess, HSN/SAC-specific rates, reverse charge, composition scheme and invoice-level rounding rules are not modelled.
  • Amounts are rounded to the nearest paisa. The total GST is rounded first; if it has an odd number of paise, the extra paisa goes to SGST.
  • This is a calculator, not tax advice. Confirm rates and invoicing rules with a qualified tax professional or the official GST sources.

How to use the GST Calculator

  1. Choose Add GST (exclusive) if your amount is the price before tax, or Remove GST (inclusive) if the amount already includes GST.
  2. Enter the amount in rupees. It must be above zero, up to ₹100 crore, with at most two decimal places.
  3. Pick the GST rate that appears on your invoice with the rate buttons, or choose Other rate and type any rate from 0 to 100 with up to two decimal places. The buttons are shortcuts only: the calculator does not know which rate applies to your item.
  4. Under Transaction type, choose Intra-state (CGST + SGST) if the supplier and the place of supply are in the same state, or Inter-state (IGST) otherwise.
  5. Read the base amount, GST amount, CGST, SGST / UTGST, IGST and final amount. Open the assumptions and calculation breakdown to see each line with your numbers, then use Copy result or Reset.

How GST is added and removed, and how to read the result

When GST is added, it is a percentage of the pre-tax price. When GST is already included, the amount is the pre-tax price plus that percentage, so the base is found by dividing by (100 + rate) and multiplying by 100. Subtracting the rate from the total directly would give the wrong answer: taking 18% off ₹1,180 gives ₹967.60, not the true base of ₹1,000.

For an intra-state supply the GST is shown as CGST and SGST, each half of the total. For an inter-state supply the whole amount is shown as IGST. Tax heads that do not apply are shown as a dash.

All maths is done in whole paise. The total GST is rounded to the nearest paisa first. In remove-GST mode the base is then the amount minus that GST, so base + GST always equals what you entered. If the GST has an odd number of paise, CGST gets the lower half and SGST gets the extra paisa, so CGST + SGST equals the GST exactly.

How to read the result: the base amount is the price before tax, the GST amount is the tax on it, and the final amount is base plus GST. In Add GST mode the final amount is what the buyer pays. In Remove GST mode the final amount is the figure you typed, and the base and GST show how it splits. The rates in the examples below are only there to demonstrate the arithmetic.

Add GST:     GST = base × rate / 100
             Final amount = base + GST
Remove GST:  Base = amount × 100 / (100 + rate)
             GST = amount - base
Intra-state: CGST = SGST = GST / 2
Inter-state: IGST = GST
  • If the price you have comes after a discount, work out the discounted price first with the Discount Calculator.
  • For any other percentage question, such as how much a price changed by, use the Percentage Calculator.

Assumptions and limits

  • GST rates and slab structures change; use the rate shown on your invoice or the official GST notification. This calculator does not know which rate applies to a given item.
  • The GST rate is whatever you select or type; it is not validated against the goods or service you are dealing with.
  • Cess, HSN/SAC-specific rates, reverse charge, composition scheme and invoice-level rounding rules are not modelled.
  • Amounts are rounded to the nearest paisa. When the total GST has an odd number of paise, the extra paisa is placed in SGST, which may differ from how your invoicing software rounds.
  • One rate is applied to the whole amount. For an invoice with several items at different rates, calculate each line separately.
  • Amounts must be above ₹0, no more than ₹100 crore and have at most 2 decimal places.
  • This is a calculator, not tax advice. Check the rate and treatment with a qualified professional or official GST sources before filing or invoicing.

Practical examples

Add 18% to ₹10,000 within one state

GST = ₹10,000 × 18% = ₹1,800, split as CGST ₹900.00 and SGST ₹900.00. The final amount is ₹11,800.

Extract 5% GST from ₹5,000 across states

Base = ₹5,000 × 100 / 105, which comes to ₹4,761.90. GST is ₹238.10, shown entirely as IGST. ₹4,761.90 + ₹238.10 = ₹5,000.

A custom rate of 3.5% on ₹1,000

Choose Other rate and enter 3.5. GST = ₹1,000 × 3.5% = ₹35.00, split as CGST ₹17.50 and SGST ₹17.50. The final amount is ₹1,035.

Frequently asked questions

How do I remove GST from a GST-inclusive price?

Choose Remove GST (inclusive), enter the total that includes GST and pick the rate. The base is the total × 100 / (100 + rate). For example, ₹1,180 that includes GST at 18% is a base of ₹1,000 plus ₹180 of GST (₹90 CGST and ₹90 SGST within a state).

When do I choose CGST + SGST and when IGST?

Broadly, a supply within one state is split into CGST and SGST, while a supply between states is charged as IGST. The calculator only applies the split you choose; it does not determine the place of supply for you.

Why is SGST sometimes one paisa more than CGST?

When the total GST has an odd number of paise it cannot be split into two equal halves. For example, adding 5% to ₹10.10 gives GST of ₹0.51, shown as CGST ₹0.25 and SGST ₹0.26, so the two add up to the GST exactly. An invoicing system may round differently.

My invoice shows a rate that has no button. What do I do?

Choose Other rate and type the rate exactly as it appears on your invoice, from 0 to 100 with up to two decimal places. For an intra-state supply, CGST and SGST each use half of that rate.

How do I know which GST rate to select?

Use the rate that applies to your goods or service according to your invoice, supplier or the official GST sources. Rates and slabs change over time, and the calculator does not look them up; it simply applies the one you pick.

Does this handle cess, reverse charge or HSN-specific rules?

No. Cess, HSN or SAC-specific rates, reverse charge and invoice-level rounding rules are not modelled. Treat the output as an estimate and confirm anything important with a tax professional.

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