Whether it’s called sales tax, VAT or GST, the basic maths of consumption tax is the same everywhere — it’s the presentation and collection method that differs by country.
Adding tax to a price
Tax amount = Price × (Tax rate ÷ 100). Total = Price + Tax amount. A $100 item with 8% sales tax costs $108 at checkout.
Working backwards from a tax-included price
Pre-tax price = Total ÷ (1 + Tax rate ÷ 100). If a $108 receipt already includes 8% tax, the pre-tax price was $108 ÷ 1.08 = $100.
Why the systems feel different
US sales tax is typically added at checkout, so the shelf price excludes it. VAT and GST, common in many other countries, are usually already built into the displayed price — the retailer collects it but the customer doesn’t see it added separately at the register.
Whichever direction you need, the free Sales Tax Calculator handles both — adding tax to a price, or extracting the pre-tax amount from a total.