GST Calculator
Add GST to a price or pull GST out of a price that already includes tax. Enter the amount and rate below, and this calculator shows the base amount, GST amount, and final amount in one step.
₹0
₹0
₹0
GST Breakdown
Visualize the proportion of the original amount and GST amount instantly.
What Is a GST Calculator?
A GST calculator works out Goods and Services Tax on a price in either direction. It can add GST to a base amount to show what the final bill will be, or it can pull GST out of a price that already includes tax, so you can see the amount before tax.
It’s built for shoppers checking a receipt, business owners pricing products, and anyone filling out an invoice who needs the numbers to match exactly. New to the topic? Our GST explained for beginners guide covers the basics before you dive into the calculator, and our roundup of best free online calculators lists other tools worth bookmarking for billing and budgeting.
What Is GST?
GST, short for Goods and Services Tax, is a tax charged on the sale of most goods and services. It’s collected by the seller at the time of sale and passed on to the government. Instead of multiple separate taxes, GST combines them into one rate applied at each stage of a sale.
Common GST slabs include 5%, 12%, 18%, and 28%, though the exact rate depends on the category of goods or service and the country’s tax rules. Always check the rate that applies to your specific product before billing a customer.
GST Formula
Final Amount (GST Inclusive) = Original Amount + GST Amount
Original Amount (from inclusive price) = Inclusive Amount ÷ (1 + GST Rate ÷ 100)
These formulas are just percentage math applied to tax. If you want to practice the underlying percentage calculations on their own, our Percentage Calculator is a good place to start.
Inclusive vs Exclusive GST
This is one of the most confusing parts of GST, so here’s the difference in plain terms.
GST Exclusive
The price does not yet include tax. GST is added on top at checkout or billing. Use the “Add GST” option above for this case.
GST Inclusive
The price already has GST built in. To find the amount before tax, GST needs to be removed, not added again. Use the “Remove GST” option above for this case.
A common error is adding GST to a price that’s already inclusive, which overcharges the tax twice. Always check whether a listed price says “inclusive of GST” or “plus GST” before calculating. Our guide to why online calculators save time explains why it’s worth double-checking with a tool instead of doing this math on paper during a busy billing day.
Step-by-Step Examples
Example 1: Adding GST
Original Amount: ₹1,000
GST Rate: 18%
Step 1: GST Amount = (1,000 × 18) ÷ 100 = ₹180
Step 2: Final Amount = 1,000 + 180 = ₹1,180
Result: The customer pays ₹1,180, of which ₹180 is GST.
Example 2: Removing GST
GST-Inclusive Amount: ₹1,180
GST Rate: 18%
Step 1: Original Amount = 1,180 ÷ (1 + 18 ÷ 100) = 1,180 ÷ 1.18 = ₹1,000
Step 2: GST Amount = 1,180 − 1,000 = ₹180
Result: The price before tax was ₹1,000, and ₹180 of the total was GST.
Business Examples
GST calculations show up constantly in day-to-day business, not just at tax filing time.
Scenario: A shop buys stock for ₹800 and sells it for ₹1,200 before tax, with 18% GST charged on the sale.
GST Charged to Customer: (1,200 × 18) ÷ 100 = ₹216
Total Invoice Amount: 1,200 + 216 = ₹1,416
The ₹216 GST is collected on behalf of the government and isn’t part of the shop’s profit. To see the actual profit on this sale, run the ₹800 cost and ₹1,200 pre-tax price through our Profit & Loss Calculator.
Running a discount alongside GST? Work out the discounted price first with our Discount Calculator, since GST is usually applied after the discount, not before. If you’re also setting aside the GST you collect into a separate savings account, our compound interest explained for beginners guide shows how those funds can grow while they wait to be filed.
Common GST Calculation Mistakes
If a price already includes GST, adding it again overcharges the customer. Check whether the amount is inclusive or exclusive before you calculate.
Tax should almost always be calculated on the discounted price, not the original price, unless your local tax rules say otherwise.
Different goods and services fall under different GST slabs. Using a flat 18% for everything can lead to under- or over-billing.
To remove GST from an inclusive amount, divide by (1 + rate ÷ 100), not just by the rate itself. A simple subtraction of the percentage gives the wrong base amount.
If your business also deals with loan interest or EMIs alongside GST billing, our Interest Calculator and Compound Interest Calculator can help you check those numbers separately, so tax and interest don’t get mixed up in your books.
Keep your billing accurate
GST is just one part of pricing a product correctly. Pair it with our other free finance tools to check discounts, margins, and interest before you finalize a price.
Frequently Asked Questions
GST stands for Goods and Services Tax, an indirect tax applied on the sale of most goods and services and collected by the seller at the point of sale.
Multiply the original amount by the GST rate and divide by 100. Add that result to the original amount to get the final, GST-inclusive price.
Divide the GST-inclusive amount by (1 + GST rate ÷ 100) to get the original amount before GST. Subtract that from the inclusive amount to find the GST portion.
Common GST slabs include 5%, 12%, 18%, and 28%, though the rate that applies depends on the category of goods or service and local tax rules.
GST is generally applied after discounts are deducted from the original price, not on the pre-discount amount. Check your local tax rules if you’re unsure.
Yes. Use “Add GST” to work out the tax you need to charge a customer, or “Remove GST” to check the pre-tax value on a bill or invoice you’ve already received.
References
The formulas used in this calculator follow standard tax accounting practice. For further reading, see:
- Goods and Services Tax Network (GSTN) — the official portal for GST rates, filing, and rules in India.
- Investopedia, “Goods and Services Tax (GST)” — a general explanation of how GST works and where it’s used globally.
- OECD, “Consumption Tax Trends” — background on how value-added and goods and services taxes are structured internationally.