Sales Tax Calculator
Sales tax sits on top of a price rather than inside it, which makes two calculations necessary: adding tax to a net price, and stripping tax out of a gross one. This calculator does both, which is what you need when reconciling receipts, pricing goods, or filing a return.
Inputs
Result
271.25
Net 250 · Tax 21.25
How the sales tax calculator works
Adding tax: total = net × (1 + rate). Tax amount = net × rate.
Removing tax: net = total ÷ (1 + rate). Tax amount = total − net. Multiplying a gross figure by the rate overstates the tax.
Combined jurisdictional rates add before application: a 6% state and 2.5% local rate is a single 8.5% applied once, not 6% then 2.5%.
Worked example: 8.5% combined rate
- Net price 1,200: tax = 1,200 × 0.085 = 102. Total = 1,302.
- Reversing from a 1,302 receipt: net = 1,302 ÷ 1.085 = 1,200. Tax = 102.
- The wrong method: 1,302 × 0.085 = 110.67, overstating tax by 8.67.
- On monthly gross sales of 260,000 that error misstates the return by about 1,730.
- For a discounted item, apply the discount first: 1,200 × 0.9 = 1,080, then tax 91.80, total 1,171.80.
Common mistakes to avoid
Applying the rate to a tax-inclusive total
The classic reverse-calculation error. Always divide by 1 plus the rate when extracting tax from a gross amount.
Using one rate across all locations
Rates vary by state, county and city, and destination-based rules mean the buyer's address often governs.
Taxing exempt categories
Groceries, prescriptions and some services are exempt or reduced-rate in many jurisdictions. Check the category before charging.
Frequently asked questions
How do I remove sales tax from a total?
Divide the total by 1 plus the rate. At 7%, a 428 total has a net of 428 ÷ 1.07 = 400 and tax of 28.
Is sales tax charged on shipping?
It depends on the jurisdiction — many tax shipping when the goods are taxable, some do not. Check local rules.
What is the difference between sales tax and VAT or GST?
Sales tax is levied once at final sale; VAT and GST are collected at each stage with credit for tax already paid.
Is tax applied before or after a discount?
After. Tax applies to the actual amount charged, so discounts reduce tax too.
Do I charge tax based on my location or the customer's?
Most modern regimes are destination-based, meaning the customer's location sets the rate once you have nexus there.
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