The Sales Tax Calculator does two pieces of visible, everyday arithmetic. Give it a price before tax and a stated tax rate to estimate the tax and tax-inclusive total. Or give it a price including tax and the same rate to estimate the pre-tax price and the tax portion already inside the total.
The calculator runs entirely in the browser. It does not collect an address, identify a taxing jurisdiction, look up current rates, decide whether an item is taxable, or prepare a tax return. Enter a rate you have already verified from a retailer, receipt, or relevant tax authority.
How to use the calculator
- Choose Price before tax if the amount shown does not yet include tax. Choose Price including tax if the receipt or advertised price already includes it.
- Enter the amount. The page formats the display as dollars, but the formula is currency-neutral as long as the amount and result use the same currency.
- Enter the applicable tax rate as a percentage. For example, enter
8.25for 8.25%. - Read the pre-tax amount, sales tax, tax-inclusive amount, and the share of the final total represented by tax.
The results update while you type. Use Reset example to restore an $85.00 pre-tax amount and an 8.25% rate.
Add tax to a pre-tax price
Let P be the price before tax and r be the tax rate as a decimal. Convert a percentage to a decimal by dividing by 100: 8.25% becomes 0.0825.
Tax = P × r
Price including tax = P + Tax
For an $85.00 item at 8.25%:
Tax = $85.00 × 0.0825 = $7.0125
Total = $85.00 + $7.0125 = $92.0125
Displayed to cents, the estimate is $7.01 tax and $92.01 total. A merchant may round tax at a different stage—for example, per line item rather than on the whole cart—so an actual checkout can differ by a cent.
For a percentage-only check such as "what is 8.25% of 85?", use the percentage calculator. If you are applying a sale or coupon before calculating tax, use the discount calculator, which makes its assumed order explicit.
Remove tax from a tax-inclusive price
Do not subtract the tax rate directly from a tax-inclusive total. A total that already includes 8.25% tax is 108.25% of the pre-tax price, not 100% minus 8.25% of the total. Instead, divide by one plus the decimal rate.
Price before tax = Tax-inclusive total ÷ (1 + r)
Tax = Tax-inclusive total − Price before tax
For a $92.01 total at 8.25%:
Price before tax = $92.01 ÷ 1.0825 ≈ $84.999
Tax ≈ $92.01 − $84.999 = $7.011
The displayed estimate rounds to $85.00 before tax and $7.01 tax. The tiny difference from the earlier unrounded example comes from starting with a total rounded to cents.
What “tax as part of total” means
The calculator also shows tax as a percentage of the tax-inclusive total:
Tax share of total = Tax ÷ Tax-inclusive total × 100
At an 8.25% tax rate, tax is about 7.62% of the final total—not 8.25%. This is expected because the stated rate applies to the smaller pre-tax base. That number can be useful when you are reverse-checking a receipt, but it does not replace the stated tax rate.
Worked shopping examples
A shelf price that excludes tax
Suppose a product is listed at $48.50 and the verified rate is 7.5%.
Tax = $48.50 × 0.075 = $3.6375
Total = $48.50 + $3.6375 = $52.1375
The calculator displays $3.64 tax and $52.14 total after cent rounding. If a store calculates several individual items separately, compare the store's line-item rounding policy before assuming an error.
A total that already includes tax
You have a tax-inclusive total of $120.00 at a verified 20% rate.
Pre-tax price = $120.00 ÷ 1.20 = $100.00
Tax = $120.00 − $100.00 = $20.00
Choose Price including tax, enter 120 and 20, and the page shows the $100.00 pre-tax estimate.
Sale price first, then tax
An $80.00 item is 15% off, then a 6% tax applies to the reduced price. First find the sale price: $80.00 × (1 − 0.15) = $68.00. Then calculate tax: $68.00 × 0.06 = $4.08. The estimated total is $72.08.
Enter the promotion into the discount calculator to see the same assumed order alongside coupon and quantity inputs. The actual order can differ when a retailer's terms say a coupon applies before a markdown, excludes a product, or has a different tax base.
Limits: a rate is not a tax determination
This tool deliberately does not claim that any particular rate is correct. Rates, taxable items, sourcing rules, exemptions, and rounding requirements can vary by place and transaction. For example, the California Department of Tax and Fee Administration explains that city and county district taxes can make total sales and use tax rates differ by location and provides a current rate-by-address resource. Its consumer guidance also notes that local district taxes can apply in addition to a statewide base rate. CDTFA: Know Your Sales and Use Tax Rate
So the calculator is appropriate for checking arithmetic after you know the inputs. It is not appropriate for deciding which jurisdiction governs an online order, determining whether food, clothing, shipping, digital goods, or a service is taxable, or calculating a business filing obligation. For a real purchase, invoice, return, or compliance decision, use the retailer's checkout and the applicable tax authority's current guidance.
The tool also does not estimate any federal deduction. The IRS states that people who elect to deduct state and local general sales taxes may use actual expenses or optional tables in the circumstances described in its guidance; that is a separate tax-filing calculation. IRS Topic No. 503: Deductible Taxes
Related calculations
The tip calculator is for restaurant gratuity and bill splitting, not general purchase-tax reversal. It applies its documented tip assumption after tax. The gas cost calculator estimates trip fuel cost from distance, fuel economy, and price per gallon; tax embedded in a pump price is outside that model.
For a loan payment or investment projection, use the loan calculator or compound interest calculator instead. Sales-tax arithmetic is a one-time percentage calculation and does not model interest, payment schedules, fees, or changing balances.