How to Calculate GST/HST: Add or Remove Tax by Hand

GST is 5% of the price before tax: $100 × 5% = $5 GST for a $105 total. To calculate GST from a tax-included total, divide by 1.05: $105 ÷ 1.05 = $100. First determine whether the supply is taxable and which rate applies, since provinces that charge HST or an additional provincial sales tax use a different combined rate. The GST/HST calculator can perform ordinary add-and-remove calculations; the examples below explain the arithmetic. If you use the separate Quick Method of accounting, read the GST/HST Quick Method guide after checking eligibility and election requirements, then use the Quick Method calculator; it is not the ordinary sales-tax calculation shown here.

Calculate tax added to a price

Tax = pre-tax price × tax rate. Add that amount to the price. In Alberta, Yukon, the Northwest Territories and Nunavut, only the 5% federal GST applies: for a $100 taxable sale, GST is $5 and the total is $105; see the GST calculator for Alberta. For a $100 taxable sale at Ontario’s 13% HST, the tax is $13 and the total is $113 (see the Ontario HST calculator). At Nova Scotia’s 14% rate, the same pre-tax price produces $14 HST and a $114 total. Federal GST and HST rates depend on the place of supply and transaction; see the CRA rate table.

Remove tax from a total

Pre-tax price = total ÷ (1 + rate). Tax is the total minus the pre-tax price. For a $113 Ontario total that includes 13% HST, $113 ÷ 1.13 = $100 and the HST is $13. Subtracting 13% of $113 gives the wrong answer because the tax rate applies to the price before tax. If you only know the GST amount rather than the total, the pre-tax price equals the GST divided by 0.05: a $12.50 GST amount implies a $250 pre-tax price.

Province/territory	Rate	Add tax: multiply by	Remove tax: divide by	$100 before tax → total
Alberta, Northwest Territories, Nunavut, Yukon	5% GST	1.05	1.05	$105.00
British Columbia	5% GST + 7% PST	1.12	1.12	$112.00
Manitoba	5% GST + 7% RST	1.12	1.12	$112.00
Saskatchewan	5% GST + 6% PST	1.11	1.11	$111.00
Quebec	5% GST + 9.975% QST	1.14975	1.14975	$114.98
Ontario	13% HST	1.13	1.13	$113.00
Nova Scotia	14% HST	1.14	1.14	$114.00
New Brunswick, Newfoundland and Labrador, Prince Edward Island	15% HST	1.15	1.15	$115.00

Standard rates only; check taxability and place of supply before relying on a row. Rounding individual invoice lines can make a cent of difference. See the reverse-tax guide for more examples.

GST with a separate provincial tax

British Columbia and Manitoba generally have a 7% provincial sales tax, while Saskatchewan generally has a 6% PST. On an ordinary $100 sale where GST and the respective general provincial rate both apply to the same pre-tax base, GST is $5; PST or RST is $7 in BC or Manitoba and $6 in Saskatchewan. The totals are $112 or $111 respectively. GST and the provincial tax are separate obligations. Check exemptions and the particular purchase before applying both rates. See the GST and PST calculator and provincial tax overview.

Special cases need a different calculation; the ordinary combined-rate shortcuts above do not apply to every product. Confirm the treatment for a specific product before relying on the general rate. See CRA’s GST/HST technical notices and the BC Provincial Sales Tax Act for exceptions.

Calculate GST and QST in Quebec

For a taxable Quebec sale where both taxes apply, calculate 5% GST and 9.975% QST on the same pre-tax price. On $100, GST is $5.00 and QST is $9.975, which rounds to $9.98 for a $114.98 total. To reverse a combined total before rounding, divide by 1.14975; reversing rounded tax lines can differ by a cent. See the Quebec calculator and Quebec tax guide.

Which rate goes on the invoice?

Use the rate for the taxable supply under the applicable place-of-supply rules; do not assume every sale is taxable simply because a calculator displays a rate. Some supplies are zero-rated or exempt and provincial taxes have their own rules. The place-of-supply guide and exempt versus zero-rated guide explain the distinction.

Show tax and supporting information as required for the transaction. See what to show on a GST/HST invoice and CRA input tax credit documentation.

Does the tax amount equal what a business remits?

Not necessarily — collected GST/HST, input tax credits and the Quick Method (see the Quick Method calculator) all affect what a business remits; see how GST is calculated for a business return.

Sources

Sources checked October 17, 2026.