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About the GST Calculator
Goods and Services Tax (GST) is India’s unified indirect tax on the supply of goods and services, replacing VAT, service tax, and excise with one framework from July 2017. Almost every invoice you issue or receive carries GST at one of the standard slabs — 0%, 5%, 12%, 18%, or 28%, with special low rates like 0.25% and 3% for specific items such as rough diamonds and gold jewellery.
Two everyday maths tasks dominate GST work: adding GST to a base price when you quote or bill (exclusive pricing), and removing GST from a tax-inclusive figure when you need the taxable value (inclusive pricing). This calculator does both. For intra-state supplies it also splits the tax into CGST (Central) and SGST (State), each half of the total rate — the split your invoice must display.
The arithmetic is simple once you see it: GST = base × rate ÷ 100, or backwards, base = gross ÷ (1 + rate ÷ 100). The tool applies it instantly, with the round-off behaviour businesses practice on cash invoices.
How to use the GST Calculator
- 1 Choose Add GST (you know the net price) or Remove GST (you know the gross, tax-inclusive price).
- 2 Enter the amount in rupees.
- 3 Type the applicable rate or tap a slab button — 5, 12, 18, or 28 percent.
- 4 Read base, GST, and gross instantly, along with the CGST/SGST split for intra-state billing.
Key features
Add and remove modes
Quote prices net of tax, or back out the taxable value from MRP-style gross figures.
Slab quick-buttons
One tap for 0.25, 3, 5, 12, 18, and 28 percent — the rates most invoices use.
CGST/SGST split
Instantly shows the half-rate components an intra-state tax invoice must print.
Two-decimal precision
Outputs formatted the way invoices round, avoiding paisa-level surprises.
Who uses the GST Calculator?
- Small businesses preparing quotes and tax invoices at the correct slab.
- Freelancers and service providers billing clients at 18% GST.
- Accountants reconciling GSTR filings by extracting taxable value from gross sales.
- Shoppers checking how much of an MRP is actually tax.
- E-commerce sellers validating platform commission calculations on gross amounts.
Tips and best practices
- Discounts shown on the invoice are generally deducted before computing GST — tax applies to the net sale value, not the MRP.
- Inter-state supplies attract IGST at the full rate instead of CGST+SGST; the totals match, but the invoice split differs.
- Keep rate slabs straight: essentials often sit at 0–5%, standard goods and services at 12–18%, luxury and sin goods at 28% plus cess.
- Composition-scheme dealers do not charge GST on bills at all — they pay a flat percentage of turnover; do not add GST to their invoices.
- Round the total tax on an invoice to the nearest rupee per Section 170 of the CGST Act; paisa-level rounding is a common audit finding.
Frequently asked questions
GST amount = base × rate ÷ 100; gross = base + GST. For example, ₹10,000 at 18% adds ₹1,800 for a gross of ₹11,800.
Base = gross ÷ (1 + rate ÷ 100). An invoice of ₹11,800 inclusive of 18% GST has a base of 11,800 ÷ 1.18 = ₹10,000 and GST of ₹1,800.
Within a state, GST splits equally into CGST (Central) and SGST (State), each at half the rate. Between states, IGST applies at the full rate to the Centre, later apportioned. The calculator shows the intra-state split.
The main slabs are 0%, 5%, 12%, 18%, and 28%, plus special rates of 0.25% and 3% for selected items, with a compensation cess on certain luxury and sin goods.
Generally yes, on the net value after discount when the discount is shown on the invoice. Seasonal discounts funded separately by brands can be treated differently — confirm with your CA for edge cases.