VAT Calculator
Split 10% value-added tax out of a supply amount or a gross total automatically.
Reference only, based on the standard 10% rate. Follow a tax professional for accurate handling.
How the split actually works
Every VAT figure is built from three numbers: the supply value (the price before tax), the VAT itself, and the total (supply value plus VAT). At the standard 10% rate they lock together in a fixed ratio of 100 to 10 to 110. Going forward, you take a supply value and multiply by 1.1 to reach the total, with the VAT being 10% of the supply value. Going backward from a VAT-inclusive total, you divide by 1.1 to recover the supply value, and the remainder is the VAT. The single most useful thing to remember is that the VAT hidden inside a gross total is the total divided by 11, not 10% of the total, because that total already contains the tax.
A worked example both directions
Forward: you quote a service at a supply value of 500,000. VAT is 500,000 times 10%, which is 50,000, so the total you bill is 550,000. Backward: a client paid you 11,000 and you need to break it out for your books. Dividing 11,000 by 1.1 gives a supply value of 10,000, and the difference of 1,000 is the VAT. Notice that 11,000 divided by 11 also gives exactly 1,000, which is the shortcut for pulling VAT straight out of a gross figure. The same logic scales to any amount: a 33,000 receipt splits into 30,000 supply value and 3,000 VAT.
Which mode to choose
- If the number in front of you does not yet include tax, use the forward (by supply value) mode. This is the case when you are pricing a service or writing a line item on a quote before tax is added.
- If the number already includes tax, use the reverse (by total) mode. This is the case for a receipt, a card payment, or a lump sum a client agreed to pay that you now need to break down.
- When in doubt, ask whether adding 10% would be double-taxing. If the figure is what the customer actually pays, it is a gross total, so you divide rather than multiply.
Where it saves time
- Writing a quote: enter the supply value and read the VAT and the final billed amount in one step, so the number on the quote matches the number on the invoice.
- Reversing a receipt or card slip: turn a single VAT-inclusive payment into supply value and VAT for expense records or bookkeeping.
- Freelance and contractor settlement: pre-calculate supply value and tax before issuing a tax invoice, so withholding and net pay are easy to reconcile.
- Sanity-checking a vendor bill: confirm that the tax line on an invoice you received really is the total divided by 11.
Common mistakes
- Taking 10% of a gross total to find the VAT. On an 11,000 total that wrongly gives 1,100, but the real VAT is 1,000, because 10% belongs to the supply value, not to the tax-inclusive total. Use divide-by-1.1 or divide-by-11 instead.
- Adding 10% to a figure that already includes VAT, which taxes the amount twice and inflates the total.
- Rounding each line item first and then summing, versus rounding the grand total once. The two paths can land a won apart, so match whichever rule your invoicing system uses.
- Assuming every transaction is 10%. Tax-exempt and zero-rated supplies, and simplified taxpayers, do not follow the plain 10% split, so the standard formula will not describe them.
Limits and cautions
- This is a reference tool built on the standard 10% rate. It does not model tax-exempt items, zero-rated exports, or simplified taxation, and it does not decide whether a given supply is taxable.
- Won-unit rounding differs by counterparty and by accounting software, so a result here can differ from a real tax invoice by about 1 won. Treat the final issuing system as the source of truth.
- The rate field is adjustable so you can model a different percentage, but changing it does not change what the law requires for a particular transaction.
- For anything that affects a real filing, confirm the exact figures and treatment with a licensed tax accountant or the national tax authority rather than relying on this estimate.
The amounts you enter are calculated only in your browser and are never sent to or stored on a server. You can enter quote and settlement figures safely.
Read the Privacy Policy →Frequently asked questions
What is the VAT rate this uses?
Korea's standard VAT rate is 10%, and the calculator defaults to 10%. The rate field is adjustable if you need to model a different percentage, but the default reflects the ordinary case. It does not apply to tax-exempt or zero-rated items, which follow different rules.
How do I extract just the VAT from a total?
Choose the by-total mode and enter the VAT-inclusive amount. The total divided by 1.1 is the supply value, and the remainder is the VAT. For example, 11,000 gives a supply value of 10,000 and VAT of 1,000. As a shortcut, VAT inside a gross total is simply the total divided by 11.
Why isn't the VAT just 10% of the price I paid?
Because the price you paid is a gross total that already contains the tax, so 10% of it overstates the VAT. On an 11,000 total, 10% would be 1,100, but the actual VAT is 1,000. The 10% applies to the supply value of 10,000, which is why you divide the total by 1.1 rather than multiply it by 0.1.
My result differs from the tax invoice by 1 won.
That comes from won-unit rounding. Depending on the counterparty or accounting software's rounding rules, and on whether line items or the grand total are rounded, the figure can differ by about 1 won. Confirm the final numbers against the actual issuing system.
Does this handle tax-exempt, zero-rated, or simplified taxpayers?
No. This tool only performs the standard 10% split and does not model tax-exempt supplies, zero-rated exports, or the simplified taxation regime. If your transaction falls into one of those categories, the plain 10% formula will not describe it and you should follow the specific rules for that case.
Are the amounts I enter stored anywhere?
No. All calculation happens only in your browser, and the amounts are never sent to or stored on a server. Nothing you type here is retained after you leave the page.