GST and QST Calculator (Quebec)
Use this tool to quickly calculate Quebec sales taxes from either a pre-tax amount or a tax-included total.
Default rates are GST 5% and QST 9.975%.
How this GST and QST calculator works
This calculator is designed for Canadian users, especially in Quebec, where both GST (Goods and Services Tax) and QST (Quebec Sales Tax) apply to many purchases. You can use it in two ways:
- Before taxes: You enter the base price, and the calculator adds GST and QST.
- After taxes: You enter the final total, and the calculator extracts the pre-tax amount plus each tax component.
Current rates and tax basics
GST (Federal)
GST is a federal value-added tax. In most examples, the rate is 5%.
QST (Quebec)
QST is Quebec’s provincial sales tax, currently 9.975% for standard taxable purchases.
How they are applied
For regular calculations in Quebec, GST and QST are each calculated from the taxable amount. This calculator follows that approach, which is the standard for everyday pricing and invoicing scenarios.
Formulas used
1) If amount is before taxes
- GST = Amount × (GST rate ÷ 100)
- QST = Amount × (QST rate ÷ 100)
- Total = Amount + GST + QST
2) If amount is after taxes (tax included)
- Subtotal = Total ÷ (1 + GST rate ÷ 100 + QST rate ÷ 100)
- GST = Subtotal × (GST rate ÷ 100)
- QST = Subtotal × (QST rate ÷ 100)
Practical examples
Example A: Price before tax is $100.00
With GST 5% and QST 9.975%:
- GST = $5.00
- QST = $9.98 (rounded)
- Total = $114.98
Example B: Tax-included total is $114.98
Using the reverse calculation:
- Pre-tax amount is approximately $100.00
- GST is approximately $5.00
- QST is approximately $9.98
Who should use this calculator?
- Freelancers and small businesses preparing estimates or invoices
- Shoppers checking final totals in Quebec
- Bookkeepers reconciling receipts and expense records
- Anyone comparing before-tax vs after-tax pricing
Common mistakes to avoid
- Using the wrong mode (before tax vs after tax)
- Forgetting to check if tax is already included in the listed price
- Applying the wrong provincial rate for your jurisdiction
- Ignoring rounding differences of 1–2 cents on some totals
FAQ
Can I edit the GST and QST rates?
Yes. The rate fields are fully editable. If rates change in the future, you can update them instantly.
Is this calculator suitable for official tax filing?
It is a practical estimation tool and helpful for day-to-day calculations. For official filing, always follow CRA/Revenu Québec guidance and your accounting records.
Why are totals sometimes off by one cent?
Currency calculations are rounded to two decimals. Depending on the transaction and rounding method, tiny differences can happen.
Final note
If you regularly buy or sell in Quebec, keeping a fast GST and QST calculator nearby can save time and reduce pricing errors. Enter your amount, choose the correct mode, and get an instant tax breakdown in CAD.