Reverse Sales Tax Calculator
Work backwards from a total that includes tax to the price before tax. Sales tax, GST (with CGST and SGST) and VAT, with the formula shown for every answer.
Built by Toolsque Team · last updated October 14, 2026 · checked against our testing process
How to remove tax from a total
- Choose Remove tax, or Add tax if you have a price before tax and want the total.
- Enter the total from your receipt or invoice. Commas are fine.
- Pick the tax type: sales tax, GST or VAT. Each sets a sensible default rate.
- Set the rate by typing it or tapping one of the common rates.
- Read the price before tax and the tax amount. For GST, choose the CGST and SGST split or IGST.
Why you cannot just take the tax rate off the total
The most common mistake with a tax-inclusive price is subtracting the rate from the total. A $108 receipt at 8% sales tax looks like it should be $108 minus 8%, which is $99.36. It is not. The tax was added to the price before tax, so the price before tax was $100 and the tax was $8.
The rate is a percentage of the price before tax, not of the total. That is why a reverse sales tax calculator divides instead of subtracting, and why every backwards calculation done in your head comes out a little too low.
The reverse sales tax formula
To find the price before tax from a total that includes tax:
- Price before tax = total ÷ (1 + tax rate)
- Tax amount = total − price before tax
- Tax rate, if you only know the two amounts = tax ÷ price before tax
Write the rate as a decimal: 8% is 0.08, so you divide by 1.08. A $54 total at 8% was $50 before tax, with $4 of tax. The calculator above shows the exact division it used under every answer, so you can check it on paper.
Shortcut table: what to divide by
For the common rates, this is the number to divide the total by, and how much of the total is tax:
| Tax rate | Divide the total by | Tax as a share of the total |
|---|---|---|
| 5% | 1.05 | 4.76% |
| 6% | 1.06 | 5.66% |
| 7% | 1.07 | 6.54% |
| 8% | 1.08 | 7.41% |
| 10% | 1.10 | 9.09% |
| 13% | 1.13 | 11.50% |
| 18% | 1.18 | 15.25% |
| 20% | 1.20 | 16.67% |
| 28% | 1.28 | 21.88% |
| 40% | 1.40 | 28.57% |
The last column is useful on its own. At 18%, the tax is 15.25% of the total, so on a total of 1,180 the tax is 180 and the price before tax is 1,000.
How to remove GST from a total amount (India)
GST works the same way. To remove 18% GST from a total, divide by 1.18. An invoice total of 11,800 is 10,000 before GST, with 1,800 of GST. For 5% GST divide by 1.05, and for 40% divide by 1.40.
On a sale within one state the GST is split in half: CGST to the central government and SGST to the state. At 18%, that is 9% CGST and 9% SGST, so the 1,800 above is 900 CGST and 900 SGST. On a sale from one state to another, the full 18% is charged as IGST. Pick the split under the GST option to see both.
Since 22 September 2025 most goods and services fall in the 5% or 18% slab, with 40% for a short list of luxury and sin goods. The older 12% and 28% rates still appear on invoices dated before then, which is why those buttons are kept.
Removing VAT from a gross price
VAT prices are usually shown with VAT included, so the reverse calculation comes up often. At the UK standard rate of 20%, divide by 1.20, or use the shortcut that VAT is one sixth of the gross price: on 120, the VAT is 20 and the net price is 100. At 5%, divide by 1.05. Rates differ by country across Europe, so set the rate printed on your receipt.
Finding your sales tax rate in the US
US sales tax is a combined rate: the state rate plus any county and city rates. Two shops a few miles apart can charge different totals for the same item. The quickest way to get the right rate is from a receipt from the same place: divide the tax shown by the subtotal. A tax of $6.30 on a subtotal of $75 is 6.30 ÷ 75 = 0.084, an 8.4% rate.
If a backwards calculation is a cent off a real receipt, that is rounding. Shops round the tax on each item or on the whole bill, and both are allowed, so a one cent difference is normal.
When a reverse tax calculation is useful
- Expense reports that ask for the amount before tax and the tax separately, when the receipt only shows the total.
- Bookkeeping, where sales tax collected is owed to the state and has to come out of your takings.
- Pricing to a round number: if you want a menu item to cost $10.00 with tax included at 8%, the price before tax has to be $9.26.
- Checking an invoice, to confirm the GST or VAT on it matches the rate it claims.
For other pricing math, the discount percentage calculator works out a sale price or the percentage taken off, and the 40% markup calculator shows how a markup turns into a selling price and margin.
Frequently Asked Questions
How do I calculate sales tax backwards from a total?
Divide the total by 1 plus the tax rate as a decimal. At 7%, divide by 1.07: a $53.50 total was $50 before tax, and the tax was $3.50.
Why is the tax not just the rate times the total?
Because the rate was applied to the price before tax, which is smaller than the total. At 10%, the tax is 9.09% of the total, not 10%.
How do I remove 18% GST from a total amount?
Divide the total by 1.18. On 1,180 that gives 1,000 before GST and 180 of GST, which is 90 CGST and 90 SGST on a sale within one state.
How do I work out VAT from a gross amount?
At 20%, divide the gross amount by 1.2 for the net price, or divide it by 6 for the VAT itself. On 240, the VAT is 40 and the net price is 200.
How do I find the tax rate if I know the total and the tax?
Subtract the tax from the total to get the price before tax, then divide the tax by that price. A $5 tax on a $105 total is 5 divided by 100, a 5% rate.
Is anything I type saved or sent anywhere?
No. The calculation runs in your browser and nothing is sent to a server.