GST Calculator

Add GST to an amount or remove GST from an inclusive amount at any rate.

100% private. Everything runs in your browser. Your data never leaves your device.

GST Calculator

Presets:
—
Base amount
—
GST amount
—
Total

What does this tool do?

This calculator adds GST to an amount or removes GST from a GST-inclusive amount, at any rate you choose. It shows the base amount, the GST amount, and the total. Free and instant.

How to use GST Calculator - Free Online Tool

  1. Enter the amount.
  2. Enter or pick the GST rate.
  3. Choose to add GST (exclusive → inclusive) or remove GST (inclusive → base).
  4. See the base, GST, and total instantly.

Example

Add 18% GST to 1,000:

Before

Amount Rate
1000 18%

After

Metric Value
GST 180
Total 1180

1000 × 18% = 180 GST; total 1180.

Excel formula alternative

Prefer a formula? You can achieve a similar result with GST:

add: total = amount * (1 + rate/100);  remove: base = amount / (1 + rate/100)

This tool handles both adding and removing GST, so you never divide when you should multiply.

When should I use this tool?

Adding GST to invoices
Extracting GST from an inclusive price
Checking tax on a purchase
Preparing quotes with tax
Bookkeeping and reconciliation
Pricing for GST-registered businesses

Frequently Asked Questions

Multiply the amount by the GST rate to get the GST, then add it to the amount. For 18%, total = amount × 1.18.

Divide the inclusive amount by 1 plus the rate. For 18%, base = amount ÷ 1.18.

No. It calculates in your browser.

Any rate you enter, plus common presets like 5%, 12%, 18%, and 28%.

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