Add GST to a base price, to find the final amount you need to pay.
GST is calculated on the base price and added to it.
Total: Base price × (1 + rate/100)
Businesses usually quote prices before tax and add GST at the bottom of the invoice. This calculator follows that order. You enter the base price and choose a GST rate, and it shows the GST amount and the total the customer will pay.
It is the everyday tool for freelancers, contractors, wholesalers and service providers raising invoices, and for buyers checking a quotation. A web developer in Noida who quotes ₹45,000 for a website knows her client will pay more than ₹45,000 once GST is added. The calculator answers: what is the tax on this quote, and what is the final amount on the invoice?
1. Note the base price B, which is the value before tax.
2. Pick the GST rate R that applies to the item or service.
3. GST = B × R ÷ 100.
4. Total = B + GST, or directly B × (1 + R ÷ 100).
5. On the invoice, show the base price, the GST, split as CGST and SGST or as IGST, and the total.
6. Round as your billing system requires, usually to the nearest paisa or rupee.
GST is charged on the transaction value of the supply, which is the price before tax plus certain costs that are part of the supply, such as packing or delivery charged by the seller. It is never charged on the GST itself. So the base must be complete before tax is applied. If the seller adds a delivery charge on the same invoice, it usually goes into the base and GST applies to it at the rate of the main supply.
Adding R% is the same as multiplying by 1 + R ÷ 100. At 5% the multiplier is 1.05, at 18% it is 1.18, and at 40% it is 1.40. This form is useful when you need totals for many items: multiply each base by the same factor. It also shows that exclusive and inclusive prices are linked by one number, so dividing a total by the multiplier takes you back to the base.
Only a supplier registered under GST can charge it. Small businesses below the registration threshold, or those in the composition scheme, do not add GST to their invoices in the usual way. So a quote without GST from a very small supplier is not necessarily wrong. If you are registered, always show GST separately on a tax invoice so that a registered buyer can claim input tax credit.
Tanvi, a freelance web developer in Noida registered under GST, has quoted ₹45,000 for building a client's website. The service attracts 18% GST.
Answer: Total price (with GST) ₹53,100; GST amount ₹8,100
Leaving out delivery or packing charges from the base when they are part of the supply.
Quoting a GST-inclusive figure and then adding GST again on the invoice.
Charging GST when you are not registered, which is not allowed.
Using the rate for goods when the supply is a service, or the other way round.
Preparing quotations and tax invoices.
Budgeting for a purchase where the vendor's quote excludes tax.
Setting up price lists that show pre-tax and final prices.
Checking a supplier's invoice arithmetic.
What GST rates are available under GST 2.0?
Since 22 September 2025, the main rates are 5% and 18%. A 40% rate applies to a short list of luxury and sin goods. Gold, silver, and gems stay at their own 3% rate.