Sales Tax / VAT / GST Calculator
Add tax to a net price, divide it back out of a gross price, or split it into CGST and SGST — with the formula, your numbers in it, shown under every result.
Results are arithmetic on the rate you enter. This tool has no jurisdiction database — rates differ by country, state and product, and they change with legislation — so you enter your rate and it does the math. Nothing here is tax advice. See the Editorial Policy.
gross = $100.00 × (1 + 0.18) = $118.00
tax = gross − net = $118.00 − $100.00 = $18.00
Build the gross price from a net one — tax added on top, the way a quote becomes a bill.
Common GST slabs — enter your own rate for anything else; the field takes decimals like 12.5.
Results update as you type. Every amount is rounded half-up to the cent, and everything runs in your browser.
How it works
- 1
Pick the direction
Add builds a gross price from a net one. Remove works backwards from a price that already includes tax. Split does what Remove does and then halves the tax into CGST and SGST shares. Switching direction keeps your rate, so the same percentage can be checked both ways.
- 2
Enter the amount
Type the price as it reads on the tag, quote or receipt — 100.00 or 1,240.50 — and the tool reads it to the cent. In Add mode that figure is the net price before tax; in Remove and Split modes it is the gross price with the tax already inside it.
- 3
Enter the rate
The chips give 5, 12, 18 and 28 percent — common GST slabs, not a rate table for your jurisdiction — and the field accepts any rate from 0 to 1000, including decimals like 12.5. Rates above 100% are computed but flagged as unusual.
- 4
Read the operation, not just the answer
Below the result cards, the exact operation the tool ran is written out with your figures substituted: gross = net × (1 + 0.18), or net = gross ÷ (1 + 0.18). Every card value comes from that one line, so the arithmetic can be checked — or redone on paper — against it.
The same 18% forwards and backwards
Start with the pair of numbers this page opens on. A net price of $100.00 with 18% added becomes $118.00 — $18.00 of tax on top. Run that $118.00 back through the Remove mode at the same 18% and it comes apart into exactly $100.00 and $18.00 again. Add and remove are inverses at the same rate, which makes them a self-check: whatever gross the Add mode produces, the Remove mode should take back apart into the net you started with.
| Operation | Input | Rate | Net | Tax | Gross |
|---|---|---|---|---|---|
| Add (net → gross) | $100.00 | 18% | $100.00 | $18.00 | $118.00 |
| Remove (gross → net) | $118.00 | 18% | $100.00 | $18.00 | $118.00 |
The inverse property survives awkward amounts and odd rates too. Adding 5% to $9.99 gives a tax of $0.4995, which rounds half-up to $0.50 and a gross of $10.49. Removing 5% from $10.49 divides by 1.05 — $10.49 ÷ 1.05 is $9.9904… — and rounds to $9.99 with the same $0.50 of tax. The round trip lands back where it started to within the single half-cent rounding each direction is allowed, which is as exact as cent-denominated money can be.
The zero case behaves as it should: a $0.00 amount at any rate produces a $0.00 tax and a $0.00 gross, rather than an error or a negative surprise. And a 0% rate leaves any amount untouched — the tax column reads zero in every mode, which is a quick way to confirm the tool is reading your inputs as you intended.
The subtraction trap
The most common error with inclusive prices is treating the rate as if it applied to the gross. On the $118.00 receipt, eighteen percent of $118.00 is $21.24, and subtracting it leaves $96.76 — a net price that no transaction ever produced. The real split is $100.00 and $18.00, because the $18.00 was calculated on $100.00, not on $118.00. The tax was baked in before the total existed, so the only way to undo it is to divide by the factor it was baked in with.
| Method on $118.00 at 18% | Working | Net | Tax |
|---|---|---|---|
| Subtract the rate from the gross (wrong) | 118.00 − 18% × 118.00 | $96.76 | $21.24 |
| Divide by one plus the rate (correct) | 118.00 ÷ 1.18 | $100.00 | $18.00 |
The wrong method always overstates the tax, and the overstatement grows with the rate: at 5% it is off by pennies on small amounts, at 28% it misallocates dollars. Both wrong answers look entirely plausible on a spreadsheet, which is what makes the trap dangerous — there is no visual signal that the base was wrong. The Remove mode's formula line exists precisely to show which operation ran: net = gross ÷ (1 + 0.18), division, with your own figures in place.
Splitting GST into CGST and SGST
In regimes that collect one tax through two governments — India's GST is the pattern — a single intra-state sale is divided at the source between the central and the state administration. An $118.00 sale at 18% GST works out to a $100.00 net price and $18.00 of tax, which is filed as $9.00 CGST and $9.00 SGST. The buyer's total never changes; only the paperwork split does. The Split mode performs exactly that: it removes the tax as the Remove mode does, then halves it.
| Amount | Rate | Net | Total tax | CGST | SGST |
|---|---|---|---|---|---|
| $118.00 | 18% | $100.00 | $18.00 | $9.00 | $9.00 |
| $1.00 | 18% | $0.85 | $0.15 | $0.08 | $0.07 |
The second row shows the odd-cent rule. A $1.00 gross at 18% hides $0.15 of tax in a $0.85 net, and half of $0.15 is $0.075 — not an amount money can be. The half-up rounding gives the extra half-cent's worth to the CGST share, $0.08 against $0.07, so the two shares always add back to the full tax no matter what the amount is. Nothing is lost in the split; it is only assigned.
The same halving applies wherever a tax is divided between administrations — central and state, federal and provincial, however the regime names its halves. Where the split is not an even 50/50, or your regime does not split its tax at all, the net and total-tax figures still stand on their own and the two halves can be ignored or scaled on paper.
Rates, slabs, and what this tool does not know
The preset chips — 5, 12, 18 and 28 percent — are common GST slabs, offered as shortcuts rather than authority. VAT in Europe runs on different scales by country and by product class; US sales tax is set state by state and often county by county; GST rates elsewhere occupy their own schedules. Because rates also change with legislation, any table bundled into a calculator would eventually disagree with the law silently. The honest design is the one this tool uses: you supply the rate, the tool supplies the arithmetic, and the formula line shows both together.
| Rate on a $100.00 net price | Tax added | Gross |
|---|---|---|
| 5% | $5.00 | $105.00 |
| 12% | $12.00 | $112.00 |
| 18% | $18.00 | $118.00 |
| 28% | $28.00 | $128.00 |
The rate field accepts anything from 0 to 1000, including decimals like 12.5, and it will compute rates above 100% — special duties and luxury levies exist — but the tool flags them as unusual so a slipped decimal gets noticed before it reaches an invoice. And like every other figure on this page, the table above is what the calculator returns for those inputs: type 100.00, tap a slab, and the cards should read exactly the rows printed here.
Frequently asked questions
Is my price tax-inclusive or tax-exclusive?
Why does removing tax divide instead of subtract?
What are CGST and SGST?
Where do the tax rates come from?
How are the results rounded?
Can the rate go above 100%, and can I use any currency?
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Last updated: October 10, 2026