Quick Answer: To add GST to a price, multiply the price by the GST rate: GST = Price × Rate ÷ 100. To find the GST already included in a price, use GST = Price × Rate ÷ (100 + Rate). For example, 18% GST on ₹10,000 is ₹1,800, making the total ₹11,800. Use the free EasifyMe GST Calculator to get the CGST, SGST or IGST split instantly.
Key Takeaways
- Use the exclusive formula when GST is added on top of a price, and the inclusive (reverse) formula when the price already contains GST.
- Under GST 2.0, effective 22 September 2025, the main slabs are 0%, 5%, 18% and 40%. The old 12% and 28% slabs were largely removed.
- For sales within the same state, GST splits equally into CGST and SGST. For sales between states, the full amount is IGST.
- Registered businesses can usually offset GST paid on purchases (Input Tax Credit) against GST collected on sales.
- Always confirm the rate for your product or service using its HSN or SAC code.
What Is GST?
GST (Goods and Services Tax) is India's indirect tax on the supply of goods and services. It is collected at each stage of the supply chain, but because businesses can claim credit for tax paid on their purchases, the final burden falls on the end consumer.
GST replaced a long list of older taxes, including VAT, service tax and excise duty, when it launched on 1 July 2017. Its biggest reset came with GST 2.0, which took effect on 22 September 2025 after the 56th GST Council meeting and simplified the rate structure.
GST 2.0 Rate Slabs at a Glance
|
Slab |
What it generally covers |
|
0% (Nil/exempt) |
Many essentials such as fresh food staples, certain educational items, and individual life and health insurance |
|
5% |
Everyday goods and services, including many packaged foods, personal care items and most medicines |
|
18% |
The standard rate for most goods and services, including many consumer durables such as ACs and TVs |
|
40% |
Luxury and demerit goods, such as certain high-end vehicles, pan masala and aerated sugary drinks |
A few special rates also exist, such as 3% on gold and silver. Tobacco products followed a separate transition. Rates are set item by item, so treat this table as a guide, not a rate list.
Note: GST rates change through official notifications. Before you invoice, confirm the current rate for your HSN/SAC code on the GST portal (gst.gov.in) or with your tax adviser. This article is educational and not tax advice.
The GST Formulas
There are only two formulas you need.
1. GST exclusive (adding GST to a base price):
GST amount = Base price × GST rate ÷ 100
Total price = Base price + GST amount
2. GST inclusive (removing GST from a final price):
GST amount = Final price × GST rate ÷ (100 + GST rate)
Base price = Final price × 100 ÷ (100 + GST rate)
A common mistake is to calculate inclusive GST by simply taking 18% of the final price. That overstates the tax, because the 18% applies to the base price, not to the total.
How to Calculate GST (Step by Step)
- Find the correct GST rate for your product or service using its HSN or SAC code.
- Decide whether your price is exclusive (GST to be added) or inclusive (GST already included).
- Apply the matching formula above to get the GST amount.
- Work out whether the sale is within your state or to another state.
- For intra-state sales, split the GST equally into CGST and SGST. For inter-state sales, charge the full amount as IGST.
Worked Examples
Example 1: Adding 18% GST to ₹10,000
A web designer in Ahmedabad bills a client in the same state ₹10,000 plus GST at 18%.
|
Item |
Amount |
|
Base price |
₹10,000 |
|
CGST (9%) |
₹900 |
|
SGST (9%) |
₹900 |
|
Invoice total |
₹11,800 |
If the client were in Mumbai instead, the invoice would show IGST of ₹1,800 rather than CGST and SGST. The total stays the same.
Try it free: Enter any amount, pick the rate and choose inclusive or exclusive in the free GST Calculator. It shows the CGST, SGST and IGST split instantly, and includes an invoice builder and an HSN/SAC rate lookup.
Example 2: Finding the GST inside an ₹11,800 price
You paid ₹11,800 for a product with 18% GST included. How much was tax?
GST = 11,800 × 18 ÷ 118 = ₹1,800
Base price = 11,800 × 100 ÷ 118 = ₹10,000
Taking 18% of ₹11,800 would give ₹2,124, which is wrong by ₹324.
Example 3: 5% GST on a ₹1,050 inclusive price
A packaged food item costs ₹1,050 including 5% GST.
GST = 1,050 × 5 ÷ 105 = ₹50
Base price = ₹1,000
Example 4: Net GST payable after Input Tax Credit
A trader buys stock for ₹50,000 plus 18% GST (₹9,000) and sells it for ₹70,000 plus 18% GST (₹12,600).
|
Item |
Amount |
|
GST collected on sales (output tax) |
₹12,600 |
|
GST paid on purchases (input tax credit) |
₹9,000 |
|
Net GST payable to the government |
₹3,600 |
The trader pays tax only on the value they added (₹20,000 × 18% = ₹3,600). This is how GST avoids "tax on tax". ITC has conditions, such as a valid tax invoice and the supplier filing their returns, so check eligibility before claiming.
How Discounts Affect GST
When a discount is shown on the invoice at the time of sale, GST is charged on the discounted price, not the original price. For example, a ₹20,000 item with a 10% discount has a taxable value of ₹18,000. At 18%, GST is ₹3,240 and the invoice total is ₹21,240.
Discounts given later, such as year-end volume discounts, follow extra conditions and are usually adjusted through credit notes. If you offer these regularly, confirm the treatment with your accountant.
What Is the Reverse Charge Mechanism?
Normally the supplier collects GST and pays it to the government. Under the reverse charge mechanism (RCM), the buyer pays the GST directly instead. It applies to specific notified goods and services, such as certain goods transport agency services and legal services from an advocate to a business. If you are a registered business receiving such supplies, you must pay the GST yourself and can usually claim it back as input tax credit.
CGST, SGST, UTGST and IGST Explained
|
Type of sale |
Tax charged |
Who receives it |
|
Within the same state |
CGST + SGST (half each) |
Centre and state |
|
Within a Union Territory without a legislature |
CGST + UTGST (half each) |
Centre and UT |
|
Between two states, or imports |
IGST (full rate) |
Centre, which then shares with the destination state |
The total tax is the same in every case. Only the label and the split change, based on where the supply takes place.
Common Mistakes to Avoid
- Using the exclusive formula on an inclusive price. Always divide by (100 + rate) when GST is already in the price.
- Using pre-GST 2.0 rates. Many items moved from 12% to 5% and from 28% to 18%. Old rate charts are unreliable.
- Charging CGST + SGST on an inter-state sale. Inter-state supplies need IGST.
- Rounding each line differently. Keep rounding consistent across your invoice to avoid mismatches in returns.
- Assuming every purchase qualifies for ITC. Some items are blocked from credit.
GST in Everyday Money Decisions
GST also shows up in places you might not expect. Loan processing fees and many bank charges attract GST, which is one reason the headline EMI rarely tells the whole story. Our guide on why zero-cost EMI is not actually free explains these hidden costs, and the Loan EMI Calculator helps you see the full loan cost.
For quick markup, discount or margin checks, try the Percentage Calculator. Saving up for a big purchase instead of borrowing? See how your savings grow with the Compound Interest Calculator. You can find all our money tools in the finance tools hub and the wider calculators collection.
How to Use the EasifyMe GST Calculator
- Open the free GST Calculator.
- Enter the amount.
- Select the GST rate, or look it up using the product's HSN or SAC code.
- Choose exclusive (add GST) or inclusive (remove GST).
- Read the GST amount, the CGST/SGST or IGST split and the final price.
- Use the invoice builder to create a GST invoice, or the ITC calculator to work out your net tax payable.
The calculator is updated for GST 2.0 rates and runs entirely in your browser.
Frequently Asked Questions
How do I calculate 18% GST on an amount?
Multiply the amount by 0.18. For ₹10,000, GST is ₹1,800, and the total is ₹11,800. For an intra-state sale, show ₹900 as CGST and ₹900 as SGST.
How do I remove GST from a total price?
Divide the total by (1 + rate). For an ₹11,800 price at 18%, the base price is 11,800 ÷ 1.18 = ₹10,000, and GST is ₹1,800.
What are the GST slabs after GST 2.0?
Since 22 September 2025, the main GST slabs are 0%, 5%, 18% and a 40% rate for luxury and demerit goods. A few special rates, such as 3% on gold, still apply.
What is the difference between CGST, SGST and IGST?
CGST and SGST are charged together, half each, on sales within a state. IGST is charged at the full rate on sales between states. The total tax is the same.
Is the EasifyMe GST Calculator free?
Yes. It is completely free, needs no signup and runs entirely in your browser, so your figures are never sent to a server.
