Softonic

GST Calculator

Step 1 / 3 GST calculation

Choose the calculation and enter an amount

Use Add GST for a price before tax. Use Remove GST for a total that already includes tax.

Calculation mode

Enter a plain number without thousands separators. Your locale decimal mark is accepted.

Use a GST rate you have already verified to add tax to a net amount or extract the tax included in a gross amount. The calculator applies one percentage to one amount and shows the net value, GST, and gross value. It does not identify the correct jurisdiction, classify a supply, combine taxes, apply exemptions, or create an invoice. Rates and rules can change, so confirm the rate, supply type, location, and transaction date with the relevant tax authority.

How to calculate GST

  1. 1

    Enter the amount

    In Add GST mode, enter the amount before tax. In Remove GST mode, enter the tax-inclusive total.

  2. 2

    Enter a verified rate

    Type the percentage that applies to your transaction, then choose whether to add or remove GST.

  3. 3

    Review the estimate

    Compare the net value, GST amount, and gross value in the same currency or unit as your input. Apply the relevant authority's invoice and rounding rules before using the result in official records.

Add or remove GST with one verified rate

To add GST to an amount before tax:

GST = net amount × (rate ÷ 100)

gross amount = net amount + GST

To extract GST from a tax-inclusive total:

net amount = gross amount ÷ (1 + rate ÷ 100)

GST = gross amount - net amount

These formulas apply one percentage to one amount. They do not decide which rate or tax treatment is legally correct.

Worked example

Suppose the amount before tax is 100.00 currency units and the verified rate is 18%:

  • GST: 100.00 × 0.18 = 18.00
  • Gross amount: 100.00 + 18.00 = 118.00

Starting with the inclusive amount gives the same split:

  • Net amount: 118.00 ÷ 1.18 = 100.00
  • GST: 118.00 - 100.00 = 18.00

The 18% rate is only an arithmetic example. It is not a recommendation for any transaction.

Illustrative official rates checked 28 July 2026

Jurisdiction Illustrative current position What to verify
India The post-reform structure has 5% and 18% as its two main rates. A 40% special rate and other scheduled rates, exemptions, and special rules also exist. Most 56th GST Council rate changes took effect on 22 September 2025, with specified tobacco products treated separately. Check the CBIC notification, HSN or SAC classification, time-of-supply rules, exemptions, and any cess.
Australia GST on an ordinary taxable supply is 10%. For a fully taxable GST-inclusive price, the GST component is generally one eleventh of the total. Check whether the sale is taxable, GST-free, input taxed, mixed, or subject to a special method.
New Zealand GST-registered suppliers generally charge 15% on most taxable supplies. Zero-rated, exempt, land, and other special supplies can differ. Check the supply category and any special rule with Inland Revenue.
Canada Other taxable supplies generally use 5% GST in non-participating provinces, 13% HST in Ontario, 14% HST in Nova Scotia, and 15% HST in the other participating provinces. Zero-rated supplies use 0%. Check the place and type of supply, the transaction date, and whether a separate provincial tax applies.
Singapore The standard GST rate is 9%. Zero-rated, exempt, and other specially treated supplies can differ. Check the supply category, time of supply, and any customer-accounting or transitional rule.

This table is a reference, not a set of automatic presets. A rate can depend on the product or service, customer, seller status, place of supply, invoice or payment date, exemptions, and transitional rules. Always verify the official rule that applies on the transaction date.

Official references: India GST Council and Ministry of Finance, Australia ATO, New Zealand Inland Revenue, Canada CRA, and Singapore IRAS.

What this calculator does not decide

  • Whether you or the supplier must register, charge, collect, report, or claim GST
  • Whether a supply is standard-rated, zero-rated, exempt, input taxed, or outside the tax system
  • How India divides tax between CGST, SGST, UTGST, or IGST, or whether cess applies
  • Whether Canada requires HST, GST plus a separate provincial tax, or a special place-of-supply rule
  • How to apportion mixed supplies or allocate tax across discounted items, shipping, fees, or partial payments
  • Which invoice-level, line-level, or cash-rounding method an authority or accounting system requires

Rounding and official records

The calculator works from the entered values and displays the result to two decimal places. An invoice or accounting system may calculate and round tax per line, per item, or on a subtotal, so its total can differ by a cent or two. Use the relevant tax authority’s rules and your accounting records for filing, invoicing, or contractual amounts.

Privacy

The amount, rate, and calculation mode stay in your browser. They are not sent to our servers or placed in the page URL. In the three-step view, the private working data is kept in this tab’s browser storage for up to 30 minutes so the next step can open it. Starting over removes it, and the browser may clear it sooner.

Frequently Asked Questions

Divide the gross amount by 1 + rate ÷ 100 to find the net amount, then subtract the net amount from the gross amount to find GST. For example, at 15%, divide by 1.15. Do not simply subtract 15% from the gross amount, because the tax is a percentage of the net amount.

Enter the rate you have verified for the transaction’s jurisdiction, supply type, customer, location, and date. The calculator does not classify a supply or select a rate. Official rates and exceptions can change, so use the relevant tax authority’s current guidance.

If HST applies, enter the full combined HST rate, such as 13%, 14%, or 15%, rather than adding 5% GST again. A separate PST or QST is outside this single-rate calculation and may use a different tax base or rule. Confirm the place-of-supply treatment with the CRA and the relevant province.

The add and remove formulas are the same for any single percentage applied to a net amount, so the calculator can perform that arithmetic. GST, VAT, HST, and sales-tax systems have different registration, exemption, place-of-supply, credit, and reporting rules. The result is not a legal classification.

Invoices may round tax per item, per line, or on a subtotal. This calculator shows a two-decimal estimate from one amount and one rate. Follow the authority’s invoice rules and use your accounting system’s method for official records.

No. The amount, rate, mode, and result are calculated in the browser and are not sent to our servers or put in the URL. The optional three-step flow keeps only a short-lived working record in this tab’s browser storage for up to 30 minutes. Starting over removes it.

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