Shopping · 5 minute read

How to calculate sales tax and the final price

Calculate the tax amount and checkout total from a price and sales-tax rate, including discounted purchases.

Quick answer: Convert the tax rate to a decimal and multiply it by the taxable price. Add that tax to the price. At a 7.5% rate, a taxable $80 purchase has $6 in tax and a $86 final total.

Find the tax amount

Convert the percentage rate to a decimal by dividing it by 100. A 7.5% rate becomes 0.075. Multiply the taxable price by that decimal to find the tax charge.

Keep enough decimal places during the calculation and round the final currency amount to the nearest cent. A register can differ by a cent when local rules require tax to be rounded item by item instead of on the full subtotal.

Sales tax = taxable price × (tax rate ÷ 100)

Calculate the final price in one step

Add 1 to the decimal tax rate and multiply once. For a 6% rate, multiply the taxable price by 1.06. A $45 purchase becomes $47.70.

Final price = taxable price × (1 + tax rate ÷ 100)

Apply a discount before calculating tax

For a typical store discount, calculate the reduced taxable subtotal first and then apply the tax rate. A $100 item with 20% off becomes $80. At 7.5% tax, the final charge is $86.

Coupon and tax rules vary by location and promotion type. Manufacturer coupons, trade-ins, delivery charges, and tax holidays may be handled differently, so the checkout total is the authority for an exact transaction.

Why the displayed price may not match the taxable amount

For planning, use the combined rate that applies where the purchase is delivered or completed. For a receipt dispute or business filing, use the official rules for that jurisdiction.

Some products or services are exempt from tax.
Different items can have different tax rates.
Shipping or service fees may be taxable in some locations.
Local taxes can be added to a wider regional rate.
Rounding rules can create a one-cent difference.

Frequently asked questions

How much is 8% tax on $50?

The tax is $4, making the final price $54.

Is sales tax calculated before or after a discount?

Ordinary store discounts usually reduce the taxable price first, but exact coupon rules vary by jurisdiction and promotion type.

How do I work backward from a tax-inclusive total?

Divide the final total by 1 plus the decimal tax rate. At 5% tax, divide by 1.05.

Want help with the calculation?

Use the discount calculator →

Published August 3, 2026 · Reviewed for clarity and source accuracy.