How to Calculate GST on a Price (Add GST & Remove GST Online)

A shop quote says ₹1,000 + GST or a receipt shows ₹1,180 inclusive of tax. You need to know how much is tax and how much is the actual price. That is what GST (Goods and Services Tax) math does on invoices, menus, and B2B quotes in India and in other countries with value-added tax.

This guide shows how to add GST to an exclusive price and how to remove GST from an inclusive total, with clear rupee examples.

Exclusive vs inclusive price

• Exclusive (ex-GST): price before tax. GST is added on top.
• Inclusive (inc-GST): price already includes tax. You split it to find the base and GST portion.

Always check the label on the quote: “+ GST” usually means exclusive; “GST included” means inclusive.

How to add GST to a price

GST amount = Base × (Rate ÷ 100)
Inclusive total = Base + GST amount

Example: 18% GST on ₹1,000 (exclusive)

1. GST = 1,000 × (18 ÷ 100) = ₹180
2. Total = 1,000 + 180 = ₹1,180

Example: 5% GST on ₹2,500

• GST = 2,500 × 0.05 = ₹125
• Total = ₹2,625

Common India GST slabs you will see on goods and services include 5%, 12%, 18%, and 28% (exact rate depends on the product category and current law—confirm on your invoice).

How to remove GST from an inclusive price

When the bill already includes GST, do not subtract 18% of the total. That gives the wrong base. Use:

Base = Inclusive ÷ (1 + Rate ÷ 100)
GST amount = Inclusive − Base

Example: 18% GST included in ₹1,180

1. Base = 1,180 ÷ 1.18 = ₹1,000
2. GST = 1,180 − 1,000 = ₹180

Why not subtract 18% of 1,180?

18% of 1,180 = ₹212.40—that is too high. The tax was calculated on the base, not on the total.

Quick reference table (add GST)

CGST and SGST (split tax)

Many Indian invoices show CGST and SGST at half the rate each (for intra-state sales). Example: 18% GST might appear as 9% CGST + 9% SGST on the same base. The total tax percent is still 18% on the exclusive amount—our combined-rate method still applies.

Inter-state sales may show IGST at the full rate instead.

GST and discounts

If a discount applies before tax, calculate GST on the discounted base.

Example: ₹1,000 list price, 10% discount → base ₹900 → 18% GST on ₹900 = ₹162 → pay ₹1,062.

If the receipt already shows a final inclusive total, use remove GST on that final number.

When to use a GST calculator

Hand math is fine for round numbers. A calculator helps when:

• The rate is 12% or 18% and the amount has paise (₹47.83)
• You are checking a supplier invoice
• You need both add and remove modes in one place

Use our free GST calculator: choose Add GST or Remove GST, pick a preset rate or enter a custom percent, and read base, GST amount, and inclusive total instantly.

For general percent problems, see the percentage calculator. For sale discounts before tax, try the discount calculator.

Frequently asked questions

How do I calculate 18% GST on ₹1,000?
Multiply 1,000 by 0.18 = ₹180 tax. Total = ₹1,180.

How do I get the price before GST from ₹1,180?
Divide 1,180 by 1.18 = ₹1,000 base. GST portion = ₹180.

Which GST rate applies to my product?
Rates depend on HSN/SAC category and government notifications. Your invoice or CA can confirm; this guide only does the math.

Is GST calculated on MRP?
Depends on the transaction and labeling. Follow what your quote or receipt states (exclusive vs inclusive).

Can I use this for VAT outside India?
The same add/remove formulas work for any single tax rate labeled as percent of base.

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Bottom line: To add GST, multiply the exclusive price by the rate and add. To remove GST, divide the inclusive price by (1 + rate). For fast checks, use the GST calculator.