One combined rate
Enter the full rate you want applied. The calculator does not split rates into state, county, city, GST, PST, or QST components.
Calculator
Sales Tax / GST-HST Calculator
Add tax to a pre-tax amount or remove included tax from a total using a user-entered rate. Supports US sales-tax wording and Canadian GST, HST, PST, QST, and combined-tax labels without automatic rate lookup.
Trust and methodology
How this calculator is reviewed
- Calculation type
- Sales-tax add/remove estimate using a user-entered rate
- Jurisdiction
- United States and Canada; no automatic state, province, territory, local, or product lookup
- Calculation rules
- sales-tax-v1
- Engine version
- Sales Tax Engine V1
- Last reviewed
- 2026-08-01
This is an informational sales-tax estimate from a user-entered rate, not tax advice, an official rate lookup, invoice compliance, filing guidance, or a government calculation.
Primary sources
- GST/HST calculator (and rates)Canada Revenue Agency - CanadaSupports add-tax and reverse-tax consumer calculation context, GST/HST rate variation, and estimate/rounding cautions.
- GST/HST rates and place-of-supply rulesCanada Revenue Agency - CanadaSupports the limitation that applicable GST/HST treatment depends on supply type and place of supply.
- General Information Concerning the QST and the GST/HSTRevenu Québec - Québec, CanadaSupports Québec-specific GST/HST and QST context without implying the calculator computes separate QST components.
- B.C. provincial sales tax (PST)Province of British Columbia - British Columbia, CanadaSupports PST context and product/exemption limitations in a non-HST province.
- Regulation 1700. Reimbursement for Sales TaxCalifornia Department of Tax and Fee Administration - California, United StatesSupports half-cent sales-tax reimbursement rounding context and tax-included price cautions.
- Sales and use tax toolsWashington Department of Revenue - Washington, United StatesSupports the limitation that local rates may require official address-based or jurisdiction-specific tools.
- Local sales & use taxWashington Department of Revenue - Washington, United StatesSupports the limitation that local sales and use tax rates change and vary by city, county, and effective period.
Known limitations
- Automatic state, province, territory, county, city, ZIP, address, or place-of-supply lookup is not included.
- The calculator accepts one combined user-entered rate and does not separately compute GST, HST, PST, QST, state, county, or city components.
- Exemptions, tax holidays, product-specific taxability, coupons, discounts, tips, delivery sourcing, marketplace rules, lodging taxes, alcohol taxes, tobacco taxes, vehicle taxes, and digital-goods rules are outside V1.
- Business invoice, filing, registration, remittance, audit, and compliance requirements are not modeled.
- Currency labels affect display only; no currency conversion is performed.
Found a calculation issue, outdated source, accessibility problem, or unclear assumption? Contact us.
Enter tax details
Defaults are examples only, not official or recommended rates. Enter the rate that applies to your transaction.
Methodology
How Sales Tax Is Calculated
In add-tax mode, the entered amount is treated as the pre-tax price. The locked engine applies the entered single combined rate and rounds the tax amount to the nearest cent.
In remove-tax mode, the entered amount is treated as a tax-inclusive total. The engine estimates the pre-tax amount from the total and entered rate, rounds that pre-tax amount to cents, and derives included tax as final total minus rounded pre-tax amount.
Cent rounding
Money values are rounded to cents using the locked engine. Official or merchant calculations can differ by a cent.
Effective rounded rate
The effective rate reflects rounded cents. For tiny purchases it can differ visibly from the entered rate.
United States and Canada Scope
For United States use, enter the combined rate that applies to the transaction. State and local rates, taxable products and services, sourcing rules, and exemptions vary and are not determined by this calculator.
For Canada, GST is federal, HST combines federal and provincial tax in participating provinces, and PST or QST may apply under separate provincial systems. This calculator accepts one combined user-entered rate and does not model place-of-supply, product, registration, filing, or remittance rules.
Worked Examples
US add tax
- Pre-tax price
- $100.00
- Rate
- 8.25%
- Tax
- $8.25
- Final total
- $108.25
Canada add tax
- Pre-tax price
- C$100.00
- Rate
- 13%
- HST
- C$13.00
- Final total
- C$113.00
Remove included tax
- Tax-inclusive total
- $108.25
- Rate
- 8.25%
- Estimated pre-tax
- $100.00
- Included tax
- $8.25
Rounding case
- Pre-tax price
- $0.05
- Rate
- 10%
- Tax
- $0.01
- Final total
- $0.06
- Effective rounded rate
- 20%
Limitations
- No state, province, county, city, territory, or address-based rate lookup is included.
- Tax holidays, exemptions, product-specific taxability, coupons, discounts, tips, delivery sourcing, and marketplace rules are not modeled.
- Lodging, alcohol, tobacco, vehicle, digital-goods, and other special tax rules are outside V1.
- Business invoice, filing, registration, remittance, and compliance requirements are excluded.
- Multiple sequential tax components and currency conversion are not modeled.
Sales Tax Calculator FAQ
How do I add sales tax to a price?
Choose Add tax, enter the pre-tax amount, and enter the combined tax rate that applies to your transaction. The locked engine returns the tax amount and final total.
How do I remove included tax from a total?
Choose Remove included tax and enter the tax-inclusive total. The calculator estimates the pre-tax amount from the entered rate, then calculates included tax as final total minus rounded pre-tax amount.
Does this calculator automatically find my tax rate?
No. V1 does not look up state, local, provincial, territorial, product, or place-of-supply rates. You enter the rate yourself.
What is the difference between GST, HST, PST, and QST?
GST is Canada's federal goods and services tax. HST combines federal and provincial tax in participating provinces. PST and QST are separate provincial systems. This calculator accepts one combined user-entered rate.
Can I enter a combined tax rate?
Yes. The calculator is designed around one combined tax rate, such as a total US sales-tax rate or a Canadian combined GST/PST-style rate.
Why can reverse tax calculations differ by a cent?
Reverse mode rounds the estimated pre-tax amount to the nearest cent and then derives tax by subtraction. Merchant systems may use transaction-specific rounding or invoice rules.
How is tax rounded?
The locked engine rounds calculated tax to the nearest cent using half-up rounding for nonnegative money values.
Can I use this for US state and local sales tax?
Yes, if you supply the combined rate yourself. The calculator does not determine state, county, city, district, sourcing, or exemption rules.
Can I use this for Canada GST/HST?
Yes, as an estimate with a user-entered rate. It does not separately calculate GST, HST, PST, or QST components.
Are tax exemptions included?
No. Exemptions, tax holidays, product-specific taxability, and special industry rules are outside V1.
Does this calculate official invoice tax?
No. It is an estimate and does not model official invoice, filing, registration, remittance, or business compliance requirements.
Can the effective tax rate differ from the entered rate?
Yes. For very small amounts, cent rounding can make the rounded effective rate differ from the entered rate. For example, $0.05 at 10% rounds to $0.01 tax, or 20% of the pre-tax amount.
Does the calculator convert currencies?
No. Currency changes only the display label. The calculation does not convert between USD, CAD, or any other currency.
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This calculator provides estimates from a user-entered tax rate. It does not determine official rates, exemptions, filing obligations, tax advice, invoice compliance, or currency conversion. Read the full disclaimer.