This GST calculator adds tax to a net amount or extracts tax from a gross amount at the rate you enter. It supports everyday invoice arithmetic for GST/VAT-style rates. Confirm the correct statutory rate and invoicing rules for your jurisdiction.
To add GST, multiply the price by (1 + rate ÷ 100): ₹1,000 + 18% GST = ₹1,180. To remove GST from a GST-inclusive price, divide by (1 + rate ÷ 100): ₹1,180 ÷ 1.18 = ₹1,000, so the GST is ₹180. Do not take 18% of ₹1,180 (that gives ₹212.40, which is wrong). Since 22 September 2025, India’s main GST slabs are 5%, 18% and 40%.
How to use this GST calculator
- Choose exclusive mode to add GST to a base price, or inclusive mode to extract GST from a tax inclusive price.
- Enter the amount and the GST rate as a percent.
- Review the tax amount and the price before or after tax, depending on the mode.
In inclusive mode the headline result shows the total (the amount you typed); read the base and GST lines below it.
Run both modes when a quote is unclear about whether GST is already included. Matching the mode to the invoice language prevents double counting tax.
The same percentage pattern also covers many VAT style questions. Labels change by country, but exclusive and inclusive arithmetic stays familiar: grow a net amount, or peel tax out of a tax included total.
What this GST calculator does
Exclusive mode treats your amount as the net base, then adds tax. Inclusive mode treats your amount as already tax included, then splits it into base and tax. Both modes show the pieces you need for quotes, invoices, and quick checks.
- Amount: net base or gross total, depending on mode
- Rate: GST or VAT percent
- Exclusive mode: add tax to net
- Inclusive mode: extract tax from gross
Formulas that match the plugin
Exclusive (add tax): tax = amount * (rate/100), total = amount + tax. Equivalently, total = amount * (1 + rate/100) with the original amount as base.
Inclusive (amount includes tax): base = amount / (1 + rate/100), tax = amount – base, total = amount. That reverse path answers how much net value sits inside a tax included sticker price.
Exclusive worked example
Amount 1000, rate 18 percent, exclusive mode. Tax = 1000 * 0.18 = 180. Total = 1180. Base remains 1000. This is the classic add GST path on a net quote.
Inclusive worked example
Amount 1180, rate 18 percent, inclusive mode. Base = 1180 / 1.18 = 1000. Tax = 180. Total stays 1180. You recovered the same net that exclusive mode started from.
| Mode | Input amount | Rate | Base | Tax | Total |
|---|---|---|---|---|---|
| Exclusive | 1000 | 18% | 1000 | 180 | 1180 |
| Inclusive | 1180 | 18% | 1000 | 180 | 1180 |
| Exclusive | 250 | 10% | 250 | 25 | 275 |
| Inclusive | 275 | 10% | 250 | 25 | 275 |
Exclusive vs inclusive prices
Use exclusive mode when your catalog or cost sheet is stored without tax and you need a customer facing total. Sales teams also use it when a manager asks for tax on top of an approved net number.
Exclusive math is also useful while drafting proposals in regions where displayed prices are commonly shown net, with tax itemized at the end.
Use inclusive mode when a shelf price, cart total, or contractor quote already embeds tax. Finance and purchasing teams reverse out the base to compare suppliers on a net basis or to understand tax share inside a lump sum.
Inclusive extraction is also a teaching tool: it shows why you should not subtract rate percent of the gross as if it were exclusive tax. The correct divisor is (1 + rate/100).
Exclusive mode taxes a net base. Inclusive mode backs tax out of a gross price. Mixing modes when comparing vendor quotes creates false savings, so keep quotes in one mode before you choose a supplier.
GST rates in 2026
| Country | Rate | Source |
|---|---|---|
| India (GST 2.0, from 22 Sep 2025) | 5%, 18%, 40% (plus 0%, 0.25%, 1.5%, 3% special rates); 12% and 28% removed | CBIC |
| Australia | 10% | ATO |
| New Zealand | 15% | govt.nz |
| Singapore | 9% | IRAS |
| Canada | GST 5%; HST 13% (ON), 14% (NS from 1 Apr 2025), 15% (NB, NL, PE) | CRA |
| UK (VAT) | 20% standard | GOV.UK |
Enter the percent printed on your invoice or provided by your accountant. India legal basis: Notification 9/2025-Integrated Tax (Rate).
Add or remove GST, worked
| Case | Price before tax | Tax | Total | Tax share of the total |
|---|---|---|---|---|
| Add 5% to ₹1,000 | ₹1,000 | ₹50 | ₹1,050 | — |
| Add 18% to ₹1,000 | ₹1,000 | ₹180 | ₹1,180 | — |
| Add 40% to ₹1,000 | ₹1,000 | ₹400 | ₹1,400 | — |
| Remove 18% from ₹500 | ₹423.73 | ₹76.27 | ₹500 | 18/118 = 15.254% |
| Remove 10% (AU) from $110 | $100 | $10 | $110 | 1/11 |
| Remove 15% (NZ) from $115 | $100 | $15 | $115 | 3/23 |
| Add 13% HST (ON) to $100 | $100 | $13 | $113 | — |
Invoice workflow tips
Keep net, tax, and gross in separate columns whenever you can. Run the calculator to validate a spreadsheet row when a total looks off. Matching exclusive and inclusive examples against each other, as in the table above, is a strong sanity check.
Currency symbols do not change the percent math. The plugin formats results as currency style numbers for readability, while the underlying relationships stay rate based.
GST invoice mistakes that break totals
- Subtracting rate percent from a gross total instead of dividing by (1 + rate/100)
- Adding tax twice because a price was already inclusive
- Using one blended rate on mixed exempt and taxable lines
- Forgetting which mode you selected when interpreting base versus total
- Treating calculator output as a filing position without professional review
For related commercial tools, explore business finance calculators and the parent business calculators hub. The full library is in the calculators archive.
Rate changes and recomputation
When a jurisdiction announces a rate change, re-run both modes on sample invoices from your files. Exclusive quotes need new totals. Inclusive shelf prices may need new bases if you hold the gross sticker constant, or new gross figures if you hold the net constant. Decide which side of the price you want to protect before you edit the catalog.
A one point rate move looks small until you multiply it across thousands of SKUs. The calculator is useful for pilot SKUs before a mass update.
Discounts and tax order
Some invoices apply discounts on net, then tax. Others advertise tax included deals with markdowns on the gross. The GST calculator does not encode every commercial discount policy. Compute the amount that exists after your discount rules, then apply exclusive or inclusive mode to that amount.
If two teammates disagree about order of operations, write the sequence in plain language next to the quote. Ambiguity about discount order creates customer disputes faster than ambiguity about currency symbols.
Related: how GST works · Profit Margin Calculator · VAT Calculator · Sales Tax Calculator · Percentage Calculator · Discount Calculator.