Sales Tax Calculator: Adding Tax, Reverse Calculations, and Tax Across Borders
Sales tax math is straightforward — multiply by (1 + rate) — but the gotchas are in the conventions. Tax-included vs tax-excluded pricing, rounding rules, and varying state and country rates make tools like this unexpectedly useful.
If something costs $100 with 8% sales tax, the final price is $108. The math is one multiplication. The complication is everything around it: working backward from a tax-included price, comparing rates across regions, deciding what's taxable and what isn't, and dealing with multi-jurisdictional sales (state + city + special district taxes).
EllyTools' calculator handles forward (price + tax) and reverse (tax-included price → pre-tax) calculations, supports custom rates, and can break down combined rates into components.
Common sales tax rates (2026, approximate)
| Jurisdiction | Rate | Notes |
|---|---|---|
| US — California | 7.25% – 10.75% | Combined state + local |
| US — Texas | 6.25% – 8.25% | Combined |
| US — Florida | 6% – 8% | Combined |
| US — Oregon | 0% | No state sales tax |
| US — New Hampshire | 0% | No state sales tax |
| UK | 20% | VAT, called 'value added tax' |
| EU | 17–27% | VAT, varies by country |
| South Korea | 10% | Most goods and services |
| Japan | 10% | Consumption tax (8% on certain food) |
| Canada | 5–15% | GST (5%) + provincial PST/HST |
| Australia | 10% | GST |
Tax-inclusive vs tax-exclusive pricing
**US** typically displays prices excluding sales tax — the $9.99 menu price becomes $10.78 at the register with 7.9% tax. **EU and UK** typically display tax-inclusive prices — the £9.99 you see is what you pay, with 20% VAT already baked in.
If you have a tax-inclusive price and need to find the pre-tax amount, divide by (1 + rate). $108 ÷ 1.08 = $100 pre-tax with 8% tax. $120 inclusive of 20% VAT = $120 ÷ 1.20 = $100 pre-tax.
Common gotchas
- •Rounding direction. Sales tax is usually rounded to the nearest cent, but the rule varies — banker's rounding, regular rounding, or always-up.
- •Per-line vs total tax. Some POS systems calculate tax on each line and sum; others sum first then tax. Results can differ by a cent on multi-item orders.
- •Origin vs destination basis. US states differ in whether tax is calculated based on the seller's location or the buyer's location.
- •Tax holidays — back-to-school weekends in some US states exempt school supplies for a few days.
- •Tax exemptions on certain goods — groceries, prescription meds, period products are exempt in many places.
Extended FAQ
Why are US prices shown without tax?
Because US sales tax varies by state, county, and city, so the same retailer would have to display different prices in different stores. EU/UK use a uniform national VAT, so inclusive pricing is practical.
How do I work backward from a receipt?
Divide the post-tax total by (1 + rate). $54 with 8% tax = $54 ÷ 1.08 = $50 pre-tax.
Can I trust the rate the calculator suggests for my city?
We provide reference rates by region. For an actual transaction, always verify the current rate with your state department of revenue (US) or HMRC (UK) — rates change.
Are my entered amounts stored?
No — runs entirely in your browser.