Reverse HST Calculator
Enter a total that already includes tax. Get the pre-tax price and the exact tax portion.
✓ Verified 2026-09-19 · sources cited below · no sign-up
Reverse HST formula
Pre-tax amount = Total ÷ (1 + rate). Tax = Total − pre-tax amount. In Ontario the shortcut is Total × 13 ÷ 113 for the HST portion. For provinces with separate GST and PST, both are applied to the same pre-tax base, so the combined rate is used for the division and then split.
Frequently asked questions
How do I reverse-calculate HST?
Divide the total by 1 plus the rate. Ontario: total ÷ 1.13 = pre-tax amount; total − pre-tax = HST. A $226.00 receipt is $200.00 + $26.00 HST.
Why not multiply the total by 13%?
Because the 13% was charged on the pre-tax price, not on the total. Multiplying the total by 13% overstates the tax. Use total × 13 ÷ 113 instead.
When would I need to remove HST?
Expense claims, input tax credits (ITCs) on your GST/HST return, splitting a tax-inclusive quote, or checking a receipt that only shows the total.
Sources: Canada Revenue Agency GST/HST rate tables. Rates verified 2026-09-19. Estimates only.