Formula
Discount amount = subtotal × discount percent ÷ 100. Taxable amount = subtotal − discount amount. Sales tax = taxable amount × tax rate ÷ 100. Final total = taxable amount + sales tax + shipping or fixed fee.
Sales Tax Calculator
Calculate sales tax, discount, shipping and final checkout total from a subtotal and tax rate, with the tax amount kept separate for receipts, quotes and classroom examples.
Worked example
Subtotal 100 with a 10% discount gives 10.00 off and a taxable amount of 90.00. At 8.25%, sales tax is 90.00 × 0.0825 = 7.425, rounded to 7.43 for money display. Final total = 90.00 + 7.43 + 0.00 = 97.43.
Professional note
Master’s Tip: keep the taxable subtotal visible. If a receipt looks wrong, the first check is usually whether the discount, exempt items, delivery charge or local-rate combination was included in the taxable base.
Regional and unit assumptions
Standard or basis: general percentage arithmetic using the user-entered combined sales tax rate. No single jurisdiction is assumed; sales tax rules vary by place, item type, exemption and invoice treatment.
Checkout proof
Discount, taxable amount, tax
Sales tax calculations go wrong when discounts and tax are blended together. The page shows discount first, tax on the taxable amount second, then shipping or fixed fees in the final total.
Visible checks
What the page now proves
- Discount line
- Taxable subtotal
- Final total audit
Assumptions and limitations
- The discount is applied before sales tax because that is common checkout arithmetic; local rules and invoices can differ.
- The entered tax rate should be the combined rate you actually want to test, including any state, city, county or special local rate where relevant.
- Shipping or fixed fees are added after the tax calculation on this page. Some jurisdictions tax delivery charges differently, so formal invoices should follow the applicable rule.
- This is arithmetic for estimates, quotes and receipt checks, not tax, legal or accounting advice.
Methodology & Accuracy
How this calculator is checked
CalculationTime pages are built around visible arithmetic: the formula, assumptions, worked example and practical limitations are shown so the result can be checked rather than simply trusted.
Formula used
Discount amount = subtotal × discount percent ÷ 100. Taxable amount = subtotal − discount amount. Sales tax = taxable amount × tax rate ÷ 100. Final total = taxable amount + sales tax + shipping or fixed fee.
Standard or basis
Standard or basis: general percentage arithmetic using the user-entered combined sales tax rate. No single jurisdiction is assumed; sales tax rules vary by place, item type, exemption and invoice treatment.
Where a calculator follows a named legal, trade or industry standard, that standard is cited visibly. Otherwise the page uses transparent general arithmetic and states its limits.Master's Tip
Master’s Tip: keep the taxable subtotal visible. If a receipt looks wrong, the first check is usually whether the discount, exempt items, delivery charge or local-rate combination was included in the taxable base.
Related calculators
Questions
How do I calculate sales tax?
Multiply the taxable amount by the sales tax rate divided by 100. For example, 90 at 8.25% gives 90 × 0.0825 = 7.425, displayed as 7.43.
Is the discount applied before sales tax?
This calculator applies the discount before tax, which is common checkout arithmetic. Check the local rule or invoice basis when the order contains exempt items, rebates or special charges.
Can I use this for any currency?
Yes. Enter all amounts in the same currency. The formula is percentage arithmetic and does not depend on dollars, euros or pounds.
Why is my receipt different from the calculator?
Real receipts can differ because of local rates, exempt products, taxable shipping, rounding per line item, marketplace fees or included tax. Use the printout as an arithmetic check, not a tax ruling.
What should I print this for?
Print it as a quote note, receipt check, purchase approval record or classroom worksheet showing subtotal, discount, taxable amount, tax rate, tax and final total.
Calculation note
Sales tax is practical percentage arithmetic attached to a legal and local rule. The formula is simple, but the taxable base is the part people often need to document: subtotal, discount, exempt items, delivery charges and local rate all affect the number printed on a receipt.
The calculation has two separate jobs
First, find the taxable amount. Second, apply the rate. Keeping those two steps separate makes the result easier to audit than a one-line total, especially when a quote, purchase order or classroom worksheet needs to show how the number was built.
The rate is local, but the arithmetic is transparent
Sales tax rates and rules vary by jurisdiction and product category. This page does not choose the legal rate for the user. It lets the user enter the rate they need to test, then shows the exact percentage calculation and final total.
Receipts can round differently
Some systems round tax per line item, while others calculate against the order subtotal. That can create small differences of a cent or two. A printable calculation record helps identify whether the difference comes from rate choice, taxable base, shipping treatment or rounding.
Sources and further readingStreamlined Sales Tax Governing Board: sales tax simplification contextTax Foundation: sales tax overview