GST Calculator
Add GST to a net amount or pull it out of a total — pick an India slab (5/12/18/28%) or an Australia/NZ/Singapore rate, or enter your own. See net, GST and gross instantly, with a CGST + SGST split for India.
What do you have?
Enter an amount to calculate GST
Educational estimate only — not tax, legal or financial advice. Confirm the exact GST/VAT rate and rules with your local tax authority.
All calculations run in your browser — nothing is sent to a server.
Adding GST and removing GST are opposite operations
Goods and Services Tax (GST) is charged as a single percentage on top of a net price, but the everyday problem comes in two directions. Sometimes you know the pre-tax price and need the tax-inclusive total — a shopkeeper pricing a product, a freelancer writing an invoice. Other times you're holding a receipt or a vendor quote that already includes GST and need to work out the underlying price and the tax component separately — for bookkeeping, expense claims, or checking that a supplier charged the right rate. This calculator handles both directions and, for India, also splits the GST amount into the CGST and SGST halves that appear separately on an Indian tax invoice.
How to use this calculator
- Choose whether you have an amount before GST (you're adding tax) or an amount after GST (you're removing it).
- Enter the amount.
- Pick a rate: tap an India slab chip (5%, 12%, 18%, 28%) or an Australia / New Zealand / Singapore chip (10%, 15%, 9%), or type any custom rate directly.
- For an intra-state Indian sale, tick Split GST into CGST + SGST to see the two equal halves that a same-state invoice must show.
- Press Calculate to see the net amount, the GST amount, and the gross total together.
The two formulas
Removing GST: net = gross ÷ (1 + rate ÷ 100), then GST = gross − net.
The second formula is a division precisely because the original tax was calculated on the smaller net figure, not on the total you're now holding — subtracting the percentage from the total instead of dividing is the single most common GST error.
Three worked examples
GST / VAT rates this calculator covers
| Country | Rate(s) | Notes |
|---|---|---|
| India | 5%, 12%, 18%, 28% | Slab depends on the product/service category; 18% is the default for most items, 28% for luxury and sin goods |
| Australia | 10% | Single flat GST rate on most goods and services |
| New Zealand | 15% | Single flat GST rate, among the highest flat rates worldwide |
| Singapore | 9% | Reached 9% in 2024 after a staged rise from 7% (2022–2024) |
CGST, SGST and IGST — same tax, split two ways
India's GST is a dual system. For a sale within one state, the rate is split exactly in half: CGST (Central GST) is collected by the central government and SGST (State GST) by the state government, so 18% GST becomes 9% + 9%. For a sale across a state border, the full rate is instead charged once as IGST (Integrated GST), which the central government later settles with the destination state. The rate a customer pays and the total revenue collected are identical either way — only the accounting split changes depending on whether the buyer and seller are in the same state.
Common mistakes
- Subtracting instead of dividing. Removing GST from a total is never "total minus rate% of total" — it always understates the net price and overstates the tax. Divide by (1 + rate/100) instead.
- Applying the wrong India slab. India's slabs are assigned by category, not chosen freely — a restaurant bill, a luxury car, and a grocery staple can sit in three different slabs, so confirm the rate that applies to the specific good or service before relying on the result.
- Forgetting cess. A handful of India's 28% items (like tobacco, aerated drinks and large cars) carry an additional compensation cess on top of GST, which this calculator does not model — treat those results as the GST portion only.
- Mixing up CGST/SGST with IGST. The split only applies within the same state; an inter-state sale uses IGST at the full combined rate, not CGST + SGST.
What this calculator doesn't do
This tool applies one flat rate to one amount — it doesn't look up which slab a specific product falls into, doesn't add cess or other surcharges, and doesn't account for exemptions, reverse charge, or composition-scheme rules. Rates also change with government notifications faster than any static reference can track. Treat the output as a quick, transparent arithmetic check, and confirm the exact rate, cess and filing treatment for your specific transaction with your local tax authority or a tax professional before relying on it for compliance.
Sources & further reading
- Goods and Services Tax Network (India) — official GST portal, slabs, registration and return filing
- Australian Taxation Office — how Australia's 10% GST is charged, claimed and reported
- Inland Revenue New Zealand — GST registration thresholds and the 15% rate
- Inland Revenue Authority of Singapore — current GST rate and tax-inclusive pricing rules
Frequently asked questions
What's the difference between adding GST and removing GST from a total?
Adding GST is a multiplication on a net (pre-tax) amount: GST = net × rate ÷ 100, and the gross total is net + GST. Removing GST works backward from a tax-inclusive total, so it's a division, not a subtraction: net = gross ÷ (1 + rate ÷ 100), and GST = gross − net. For example, at 18% GST a net amount of 1,000 becomes 1,180 gross (GST of 180). Going the other way, a gross total of 1,180 divides back to a net of exactly 1,000 — subtracting 18% from 1,180 would wrongly give 967.60, off by more than 32.
What are the current GST rates in India, Australia, New Zealand and Singapore?
India uses four main GST slabs — 5%, 12%, 18% and 28% — assigned by product or service category, with 18% covering most goods and services and 28% reserved for luxury and sin goods (plus cess on some items). Australia charges a flat 10% GST on most goods and services. New Zealand charges 15% GST, one of the higher flat rates worldwide. Singapore's GST is 9% as of 2024, after a staged increase from 7% between 2022 and 2024. This calculator's quick-select chips cover all seven common rates.
What's the difference between CGST, SGST and IGST in India?
For a sale within the same state, India splits the GST rate into two equal halves: CGST (Central GST) goes to the central government and SGST (State GST) goes to the state government — each is exactly half the total GST rate, so 18% GST becomes 9% CGST + 9% SGST. For a sale between two different states, the full rate is instead charged as a single IGST (Integrated GST), which the central government later apportions to the destination state. The total tax collected is the same either way — CGST+SGST and IGST are just different ways of splitting the same GST rate depending on whether the transaction crosses a state border.
Why does removing GST use division instead of just subtracting the percentage?
Because the tax rate was applied to the smaller net amount, not to the larger total you're holding. Subtracting the rate straight from the total assumes the rate applies to the total itself, which overstates the tax removed and understates the net price. Dividing by (1 + rate ÷ 100) correctly reverses the original multiplication, so a 1,180 total at 18% GST divides back to exactly 1,000 net — not the 967.60 you'd get by simply subtracting 18%.
Is this GST calculator tax advice, and is my amount sent anywhere?
No to both. This tool performs a fixed arithmetic calculation — it is not tax, legal or financial advice, and GST/VAT rules vary by product category, exemption and jurisdiction, so confirm the exact rate that applies to your transaction with your local tax authority or a professional. Every calculation runs entirely in your browser: the amount and rate you enter are never uploaded or stored on a server, and your last input is saved only in your own browser's local storage.