GST Calculator

The GST Calculator converts a goods and services tax price between GST-exclusive and GST-inclusive amounts. Choose whether the amount you know is the net price before GST or the gross price after GST, enter the rate, and the calculator shows the GST amount, net price, gross price, and rate. It is useful for checking quotes, receipts, invoices, marketplace listings, and price tags in countries that use a GST-style value-added tax.

This page is deliberately separate from the sales tax calculator. Sales tax is commonly a U.S. point-of-sale tax collected at the final retail sale. GST is generally a broad consumption tax charged on taxable supplies, with registered businesses accounting for tax collected on sales and tax paid on business inputs. GST is also distinct from the VAT calculator page because GST countries often have their own terminology, rate structures, registration rules, and invoice requirements even when the price arithmetic is similar.

Net price versus gross price

Use Net price when the amount is GST-exclusive. This is common in business quotes, supplier cost analysis, and internal margin calculations. The calculator adds GST to show the customer-facing gross amount.

Use Gross price when the amount already includes GST. This is common for consumer prices in many GST jurisdictions. The calculator removes the embedded tax by dividing the gross price by one plus the GST rate. It then reports the GST amount as the difference between gross and net.

The GST rate must come from the applicable jurisdiction and product category. Canada, New Zealand, Singapore, Australia, and other GST systems do not all use the same rate or rules. Some supplies can be zero-rated, exempt, out of scope, or subject to combined federal and provincial components. The calculator accepts any nonnegative rate so that the arithmetic can match the rule you have already confirmed.

Formula used by the calculator

When adding GST to a net price:

$\text{gross price} = \text{net price} \times \left(1 + \frac{\text{GST rate}}{100}\right)$

The tax amount is the spread between gross and net:

$\text{GST amount} = \text{gross price} - \text{net price}$

When removing GST from a gross price:

$\text{net price} = \frac{\text{gross price}}{1 + \frac{\text{GST rate}}{100}}$

The form does not apply rounding at each supply-chain stage. It calculates one line item from one amount and one rate, then formats the displayed results as currency.

Worked example

With Net price selected, enter $100.00 and a GST rate of 10%. The calculator converts the rate to 0.10 and computes:

$\text{gross price} = 100.00 \times \left(1 + \frac{10}{100}\right) = 110.00$

The GST amount is:

$\text{GST amount} = 110.00 - 100.00 = 10.00$

The result panel therefore shows Gross price including GST: $110.00, GST amount: $10.00, Net price: $100.00, Gross price: $110.00, and GST rate: 10%. If you switch to Gross price, enter $110.00, and keep the rate at 10%, the calculator divides 110 by 1.10 and returns $100.00 as the net price before GST. The tax amount remains $10.00.

How GST fits into a tax system

GST is a consumption tax on supplies of goods and services. In a typical GST system, a registered business charges GST on taxable sales, receives GST from customers, and may claim credits for GST paid on business purchases. The business then reports the net amount to the tax authority. The final consumer generally bears the cost because they do not claim input credits.

That system design is why GST-inclusive and GST-exclusive prices both matter. A consumer usually cares about the gross amount paid. A business may need the net amount for revenue, expense, and margin records, while the GST amount goes to a tax payable or receivable account. Incorrectly treating the gross price as the tax base can overstate tax and understate net revenue.

For cross-border sales, imports, digital services, and marketplace transactions, the place where GST is charged can depend on rules that are not visible in a simple price. Use this calculator only after you have identified the correct rate and tax treatment for the supply.

Tips and limitations

• Confirm the current GST rate and category before issuing an invoice.
• Do not subtract 10% from a GST-inclusive price to remove 10% GST; divide by 1.10.
• Keep currencies consistent. This calculator does not convert exchange rates.
• Use the budget calculator for household cash-flow planning after GST, the percent off calculator for discounts before tax, and the price per unit calculator for comparing GST-inclusive shelf prices.
• Treat the result as informational only. GST rates, registration thresholds, invoicing rules, input tax credit rules, and filing obligations change by jurisdiction. Consult official guidance or a tax professional for compliance.

Sources

• Canada Revenue Agency, GST/HST for businesses — official Canadian goods and services tax and harmonized sales tax guidance.
• Inland Revenue New Zealand, GST — official GST registration, charging, and filing guidance.
• Inland Revenue Authority of Singapore, What GST is and how it works — official Singapore GST guidance.