Finance
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VAT / Sales Tax.
Calculate tax inclusive and exclusive prices
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Breakdown:
How to Use
Adding tax: Use this when you have a price before tax and want the final price.
Removing tax: Use this when the price already includes tax and you need the base price.
Common mistake: Don't subtract the tax rate percentage from the gross price. You must divide by (1 + tax rate).
FAQs
How do I add VAT or sales tax to a price?
To add tax, multiply the net price by the tax rate (as a decimal) and add it to the original price. For example, to add 20% VAT to $100: $100 × 0.20 = $20 tax, so gross price = $120.
How do I remove VAT or sales tax from a price?
To remove tax, divide the gross price by (1 + tax rate). For example, to remove 20% VAT from $120: $120 / 1.20 = $100 net price. This is NOT the same as subtracting 20%!
Why can't I just subtract the percentage to remove tax?
Because percentages work on different base amounts. If you add 20% to $100 you get $120, but 20% of $120 is $24, not $20. You must divide by (1 + rate) to correctly reverse the calculation.
What's the difference between VAT and sales tax?
VAT (Value Added Tax) is typically included in displayed prices in Europe and charged at each stage of production. Sales tax in the US is usually added at checkout and only charged once at the point of sale. Mathematically, they work the same way.
Cite this calculator
Canonical URL: https://mathify.one/en/finance/sales-tax
Cite as: Mathify. (2026). VAT / Sales Tax. https://mathify.one/en/finance/sales-tax
Use Cases
Budgeting for a purchase
Determine the total cost including sales tax before you go to the store or make an online purchase, so you can plan your spending accurately.
Example: You want to buy a $500 laptop and your local sales tax is 8%. The calculator shows you'll pay $540 in total.
Checking a receipt
Verify that the sales tax charged on a receipt is correct by entering the pre-tax price and the tax rate, or by entering the final price and tax amount to find the pre-tax price.
Example: Your receipt shows a final price of $107.50 with a 7.5% tax rate. The calculator confirms the pre-tax price was $100.
Frequently Asked Questions
- How do I use the sales tax calculator?
- Enter any two of the three values: pre-tax price, sales tax amount, or final price. The calculator will compute the missing value. For example, enter the pre-tax price and the sales tax rate to get the tax amount and final price.
- Can I calculate the pre-tax price from the final price?
- Yes. Enter the final price and the sales tax rate (or tax amount) to find the pre-tax price. The calculator will reverse the tax addition to give you the original amount before tax.
- What if I only know the sales tax rate and the final price?
- You can still use the calculator. Enter the final price and the tax rate (as a percentage) to find the pre-tax price and the tax amount. The calculator handles the math for you.
Tips & Common Mistakes
Tips
- Always enter the sales tax rate as a percentage (e.g., 8 for 8%), not as a decimal (0.08).
- If you know the tax amount but not the rate, you can enter the pre-tax price and the tax amount to find the rate.
- Double-check that you are using the correct tax rate for your location, as rates can vary by city, county, and state.
- Use the calculator to compare prices across different tax jurisdictions to see the true cost difference.
Common Mistakes to Avoid
- Entering the tax rate as a decimal instead of a percentage (e.g., 0.08 instead of 8) leads to incorrect results.
- Confusing the pre-tax price with the final price when entering values, especially when you have a receipt that shows the total.
- Forgetting that some items are tax-exempt; the calculator assumes a uniform tax rate, so adjust for exempt items manually.
Last updated: August 13, 2026