🧾 GST Calculator, Add or Remove GST Instantly
By Shihab Mia · Reviewed by ToolNimba Editorial Review, tax and finance content · Updated 2026-07-25
This calculator is for general estimates only and is not tax advice. GST rates, rounding rules and the items that are taxable, zero-rated or exempt differ by country and change over time. Always confirm the current rate and rules with your local tax authority or a qualified accountant before relying on a figure for an invoice or a tax return.
To add GST, multiply the net price by the GST rate and divide by 100 to get the GST amount, then add it to the net price for the total (GST = amount x rate / 100). To remove GST from a price that already includes it, divide the total by (1 + rate / 100), not subtract the rate directly. This calculator does both: enter a net amount to add GST and see the tax and gross total, or enter a GST-inclusive total to remove GST and find the original net price. Set your own rate, for example 10% (Australia), 15% (New Zealand) or 5%/18%/40% (India), and the net, GST, and total update instantly so you can build or check an invoice in seconds.
What is the GST Calculator?
GST is a value-added tax charged as a percentage of a sale price. The maths is simple but it runs in two directions, which is where people get caught out. To add GST to a net (GST-exclusive) amount you multiply by the rate: GST = amount x rate / 100, and the gross total = amount + GST. At a 10% rate, a $100 net price carries $10 of GST and a $110 total.
The harder direction is removing GST from a price that already includes it. You cannot simply take 10% off a GST-inclusive total, because the 10% was charged on the smaller net figure, not on the gross. Instead you divide by (1 + rate / 100). At 10%, a $110 inclusive total divides by 1.10 to give a $100 net price, leaving $10 of GST. Taking a flat 10% off $110 would wrongly give $99, so the divide-back method matters whenever you need to separate the tax from a shelf price or a receipt.
GST is known by different names and rates around the world: it is GST in Australia, New Zealand, India, Canada and Singapore, and VAT in the UK, the European Union and many other countries, but the add and remove arithmetic is identical. The rate is the only thing you change. Because GST is ultimately paid by the final consumer, registered businesses generally collect it on sales and reclaim it on purchases, so working cleanly between net, GST and gross figures is a routine part of invoicing and bookkeeping.
In India, GST on a single transaction is split differently depending on where the buyer and seller are located. For an intra-state sale (both parties in the same state), the total GST rate is divided equally into CGST (Central GST) and SGST (State GST). An 18% rate on an intra-state sale becomes 9% CGST plus 9% SGST, collected by the central and state governments respectively. For an inter-state sale (buyer and seller in different states), the full rate is charged as a single IGST (Integrated GST) line instead, collected by the central government and then apportioned to the consuming state. The total tax amount is identical either way; only how it is labelled and split on the invoice changes. A GST invoice in India shows the HSN (goods) or SAC (services) code alongside the CGST/SGST or IGST breakdown, not just one combined "GST" line.
India also restructured its GST rate slabs under the GST 2.0 reform, which the GST Council approved in September 2025 and took effect from 22 September 2025. The old four-tier structure of 5%, 12%, 18% and 28% was simplified to mainly two standard slabs, 5% and 18%, with a new 40% slab for select luxury and sin goods such as tobacco, pan masala and certain high-end items, plus a 0% (nil) rate on essentials like most dairy products and specified life-saving drugs. Most items previously at 12% moved down to 5%, and most items previously at 28% moved down to 18%. Because rates can differ by product category and change with future Council meetings, always check the current rate for the specific item on the official GST portal or with your accountant before filing, rather than assuming a rate from memory.
When to use it
- Adding GST to a quote or invoice so the customer sees the net price, the GST, and the total they will pay.
- Removing GST from a GST-inclusive shelf price or receipt to find the net amount for your bookkeeping.
- Checking that the GST line on a supplier invoice has been calculated correctly.
- Comparing a GST-exclusive quote with a GST-inclusive one so you are comparing like with like.
- Splitting an Indian GST amount into CGST and SGST for an intra-state invoice, or checking an IGST figure for an inter-state one.
- Estimating GST on a purchase under the new 5%, 18% or 40% India rate slabs before checking the exact HSN/SAC rate.
How to use the GST Calculator
- Choose a mode: Add GST to work from a net price, or Remove GST to work back from a GST-inclusive total.
- Enter the amount (the net price in Add mode, or the gross total in Remove mode).
- Enter the GST rate, or tap one of the quick-rate buttons. The default is 10%.
- Read off the net amount, the GST amount, and the total with GST.
- For an Indian intra-state invoice, halve the GST amount shown to get the CGST and SGST split; for an inter-state invoice, the full GST amount is the IGST.
Formula & method
Worked examples
Add 10% GST to a net price of $200.
- GST = 200 x 10 / 100 = $20.00
- total = 200 + 20 = $220.00
Result: Net $200.00, GST $20.00, total $220.00
Remove 10% GST from a GST-inclusive total of $550.
- net = 550 / (1 + 10 / 100) = 550 / 1.10 = $500.00
- GST = 550 - 500 = $50.00
Result: Net $500.00, GST $50.00, total $550.00
Add 15% GST to a net price of $80.
- GST = 80 x 15 / 100 = $12.00
- total = 80 + 12 = $92.00
Result: Net $80.00, GST $12.00, total $92.00
Add 18% GST to a Rs 1,000 intra-state sale in India and split it into CGST and SGST.
- GST = 1000 x 18 / 100 = Rs 180
- CGST = SGST = 180 / 2 = Rs 90 each
- total = 1000 + 180 = Rs 1,180
Result: Net Rs 1,000, CGST Rs 90, SGST Rs 90, total Rs 1,180
Adding GST at 10% to common net amounts
| Net amount | GST (10%) | Total with GST |
|---|---|---|
| $50.00 | $5.00 | $55.00 |
| $100.00 | $10.00 | $110.00 |
| $250.00 | $25.00 | $275.00 |
| $1,000.00 | $100.00 | $1,100.00 |
GST and VAT standard rates in selected countries (check current rates before use)
| Country | Tax name | Standard rate |
|---|---|---|
| Australia | GST | 10% |
| New Zealand | GST | 15% |
| India | GST | 5% and 18% standard, 40% on luxury/sin goods, 0% on essentials |
| Singapore | GST | 9% |
| United Kingdom | VAT | 20% |
India: CGST/SGST vs IGST split on an 18% rate example of Rs 1,000 net
| Supply type | Tax charged | Amount |
|---|---|---|
| Intra-state (same state) | CGST 9% + SGST 9% | Rs 90 + Rs 90 = Rs 180 total |
| Inter-state (different states) | IGST 18% | Rs 180 total (single line) |
Common mistakes to avoid
- Subtracting the rate to remove GST. Taking 10% off a $110 GST-inclusive total gives $99, which is wrong. The 10% was charged on the $100 net price, not on the $110 gross, so you must divide by 1.10 to get $100 back.
- Mixing inclusive and exclusive prices. Comparing a GST-exclusive quote against a GST-inclusive one makes the inclusive one look dearer than it is. Put both on the same basis (net or gross) before you compare.
- Using the wrong rate. GST and VAT rates differ by country and some items are zero-rated or exempt. Using the default rate for a country with a different rate, or for an exempt item, will overstate or understate the tax.
- Ignoring rounding rules. Tax authorities have specific rounding rules for invoices, often to the nearest cent per line or per invoice. Small rounding differences are normal, so match the convention your jurisdiction requires.
- Charging CGST/SGST on an inter-state sale, or IGST on an intra-state one. In India, the tax type depends on where the buyer and supplier are located, not on the tax rate itself. Charging CGST and SGST on an inter-state invoice (or IGST on an intra-state one) is a compliance error even if the total tax amount happens to be correct.
- Assuming an old India rate slab still applies. India moved most 12% items to 5% and most 28% items to 18% under the GST 2.0 reform effective 22 September 2025, and added a 40% slab for select luxury and sin goods. Using a pre-reform rate from memory can produce the wrong invoice figure.
Glossary
- GST
- Goods and Services Tax, a consumption tax added as a percentage of the price of most goods and services.
- VAT
- Value Added Tax, the name used for the same kind of consumption tax in the UK, the EU and many other countries.
- Net (GST-exclusive)
- The price before GST is added.
- Gross (GST-inclusive)
- The price after GST has been added, which is what the customer actually pays.
- Input tax credit (ITC)
- GST a registered business has paid on its purchases, which it can usually reclaim against the GST it collects on sales.
- CGST
- Central GST, the central government half of the tax charged on an intra-state (same-state) sale in India.
- SGST
- State GST, the state government half of the tax charged on an intra-state (same-state) sale in India, equal to the CGST amount.
- IGST
- Integrated GST, the single tax charged on an inter-state (cross-state) sale in India, collected by the central government and shared with the consuming state.
- HSN/SAC code
- Harmonised System of Nomenclature (goods) or Services Accounting Code (services), the classification codes used on Indian GST invoices to identify which rate slab an item falls into.
Frequently asked questions
How do I add GST to a price?
Multiply the net price by the GST rate and divide by 100 to get the GST, then add it to the net price for the total. At 10%, a $100 net price gives $10 GST and a $110 total. The Add GST mode does this for you.
How do I remove GST from a GST-inclusive price?
Divide the GST-inclusive total by (1 + rate / 100). At 10% you divide by 1.10, so a $110 inclusive total becomes a $100 net price with $10 of GST. Use the Remove GST mode for this.
Why can I not just subtract 10% to remove GST?
Because the 10% was charged on the smaller net amount, not on the larger gross total. Subtracting 10% from $110 gives $99, but the correct net price is $100. You must divide by 1.10 instead of subtracting 10%.
What GST rate should I use?
Use the standard rate for your country, for example 10% in Australia, 15% in New Zealand, 9% in Singapore, or 5%/18% (with 40% on luxury and sin goods) in India, unless the item is zero-rated or exempt. Rates change over time, so confirm the current rate with your tax authority.
What is the difference between CGST, SGST and IGST?
CGST and SGST together apply to sales within the same Indian state, splitting the GST rate equally between the central and state governments, for example 9% CGST plus 9% SGST on an 18% rate. IGST applies to sales between different states as a single combined rate, for example 18% IGST, collected by the central government and shared with the buyer state.
What are the current GST rates in India after the GST 2.0 reform?
From 22 September 2025, India mainly uses a two-slab structure of 5% and 18%, with 0% on essentials like most dairy and specified life-saving drugs and a 40% slab for select luxury and sin goods such as tobacco and pan masala. This replaced the earlier 5%, 12%, 18% and 28% structure, with most former 12% items moving to 5% and most former 28% items moving to 18%.
Is GST the same as VAT?
They are essentially the same kind of consumption tax under different names. GST is used in Australia, New Zealand, India, Canada and Singapore, while VAT is used in the UK, the EU and elsewhere. The add and remove calculations are identical.
When does a business have to register for GST?
The threshold depends on the country. Australia requires GST registration once turnover reaches AU$75,000 (AU$150,000 for non-profits), New Zealand requires it at NZ$60,000 of taxable turnover in any 12-month period, and India requires it at Rs 40 lakh turnover for goods suppliers or Rs 20 lakh for service suppliers in most states (lower thresholds apply in special category states). Confirm the current figure with your local tax authority, as thresholds change.
What is an HSN or SAC code and why does it matter for GST?
HSN codes classify goods and SAC codes classify services on an Indian GST invoice, and the code determines which rate slab (0%, 5%, 18% or 40%) applies to that specific item. Using the wrong code can result in charging the wrong GST rate even if the arithmetic is correct.
Does this calculator store my figures or send them anywhere?
No. Everything runs in your browser, so your amounts never leave your device and nothing is sent to a server. Refreshing the page clears the inputs.
Sources
- GST for business , Australian Taxation Office
- Registering for GST , Australian Taxation Office
- How VAT works , UK Government (GOV.UK)