GST calculator
Add GST to a price, or take it out of a price that already includes it. Shows the CGST and SGST split (or IGST) and the total in words, rounded to the paisa like an invoice.
How GST is calculated
Adding GST: GST = price × rate ÷ 100, and the total is price + GST. ₹1,000 at 18% is ₹180 of GST, ₹1,180 in all.
Removing GST from an inclusive price: price before tax = total × 100 ÷ (100 + rate). ₹1,180 including 18% GST is ₹1,000 before tax and ₹180 of GST. (Taking 18% off ₹1,180 would give the wrong answer, ₹967.60.)
CGST and SGST: on a sale within a state the GST is split in half, central and state: 18% becomes 9% CGST + 9% SGST. On a sale between states it is charged as one IGST at the full rate.
GST rates
Since 22 September 2025 most goods and services fall in two GST slabs, 5% and 18%, with a 40% rate for luxury and “sin” goods. A few items keep special rates, such as 3% on gold, and some are exempt. Check the current rate for your item on the official GST portal; you can type any rate under “Other”.
GST keys on a calculator
Calsee’s Business mode puts +GST and −GST keys on the keypad, shows the CGST and SGST split above every answer, keeps a running grand total and writes the amount the way a cheque needs it. Free, no ads, works offline.
Questions
How do I calculate 18% GST on ₹1,000?
₹1,000 × 18 ÷ 100 = ₹180 of GST, so the total is ₹1,180: CGST ₹90 and SGST ₹90 within a state, or IGST ₹180 between states.
How do I remove GST from a price that includes it?
Divide by (1 + rate ÷ 100). For an 18% inclusive price, divide by 1.18: ₹1,180 ÷ 1.18 = ₹1,000 before tax, and the GST is the difference, ₹180.
What is the difference between CGST, SGST and IGST?
CGST (central) and SGST (state) are charged together on a sale within one state, half the rate each. IGST is charged instead on a sale from one state to another, at the full rate.
How is GST rounded?
This calculator rounds the GST (when adding) or the price before tax (when removing) to the nearest paisa, and the other figures follow, so price + GST always equals the total.