The GST Calculator lets you add tax to a net price or pull tax out of a gross price at any rate you choose. Whether you're preparing an invoice, checking a supplier bill, quoting a client or budgeting a purchase, it gives you the net, tax and gross amounts in one step.
How GST works
GST is a value-added consumption tax: businesses charge it on outputs and reclaim it on inputs, so the final tax burden falls on the end consumer. The core arithmetic is identical whether the tax is called GST (India, Australia, New Zealand, Singapore, Canada), VAT (UK, EU) or sales tax.
The formulas
- Add GST: Gross = Net × (1 + rate/100); Tax = Net × rate/100
- Remove GST: Net = Gross ÷ (1 + rate/100); Tax = Gross − Net
- Reverse-check: Tax ÷ Net × 100 should equal the rate.
Worked examples
Adding 18% GST
Net price 1,000 → Tax = 180 → Gross = 1,180.
Extracting 10% GST
Gross price 2,200 → Net = 2,200 ÷ 1.10 = 2,000, Tax = 200.
Extracting 20% VAT
Gross 600 → Net = 600 ÷ 1.20 = 500, VAT = 100.
Common GST / VAT rates
- India — 5%, 12%, 18%, 28% (slab-based).
- Australia — 10% GST.
- New Zealand — 15% GST.
- Singapore — 9% GST.
- Canada — 5% GST (plus provincial PST/HST).
- UK — 20% VAT standard, 5% reduced.
- EU average — 19–25% VAT.
Who uses this calculator
- Freelancers and consultants preparing tax-inclusive invoices.
- E-commerce sellers reconciling gross sales into net revenue.
- Small businesses filing quarterly GST/VAT returns.
- Buyers verifying that a supplier's tax figure is correct.
Tips and common mistakes
- Never subtract the rate directly — 18% off a 1,180 gross is not 1,000. Always divide by 1 + rate.
- Round only at the end. Rounding the tax and net separately can produce mismatched totals.
- Check whether the price you see is tax-inclusive or tax-exclusive before quoting.
- Track input tax credits separately — they offset your output GST liability.
Frequently asked questions
What is GST?+
GST (Goods and Services Tax) is a value-added consumption tax charged on most goods and services. It's known as VAT in Europe, HST in parts of Canada and consumption tax in Japan, but the maths is identical.
How do I add GST to a price?+
Multiply the net price by (1 + rate ÷ 100). Example: 1,000 at 18% GST becomes 1,000 × 1.18 = 1,180.
How do I remove GST from a gross price?+
Divide the gross price by (1 + rate ÷ 100). Example: 1,180 at 18% GST → 1,180 ÷ 1.18 = 1,000 net, 180 tax.
Which GST rate should I use?+
Use the rate that applies where the sale takes place. Common examples: India 5/12/18/28%, Australia and New Zealand 10/15%, Singapore 9%, UK VAT 20%, Canada GST 5% (plus PST/HST).
Does the calculator work for VAT and sales tax?+
Yes. GST, VAT, HST and sales tax all use the same add/remove formulas — just enter your local rate.