VAT Calculator
Value-added tax runs in two directions and only one of them is obvious. Adding VAT to a net price is a simple multiplication; pulling it back out of a VAT-inclusive price requires division, and getting that wrong quietly misprices invoices. Both modes below use your rate — rates differ by country and category, so you supply the one that applies.
Add VAT to a net price
Example: net 100 at 20% → gross 120 (VAT 20).
Remove VAT from a gross price
Example: gross 120 at 20% → net 100 (VAT 20).
For a worked walk-through of both directions — why adding VAT is a multiplication, why removing it is a division, and the reason the two are exact inverses — see the companion guide VAT added and removed, one of the full set of Sumvia guides. The notes on this page document what the calculator above does with whatever rate you type, step by step.
The two formulas
Adding: gross = net × (1 + rate ÷ 100), so VAT = gross − net. Removing: net = gross ÷ (1 + rate ÷ 100) — division, because the tax was a percentage of the net, which is the smaller number. Both worked examples above (100 → 120, and 120 → 100) were computed at build time by the same engine wired into the forms, and they round-trip exactly: add then remove at the same rate and you are back where you started.
The rate is the only assumption, and it is yours: the calculator ships no rate table and makes no claim about which figure applies to your transaction. It takes any rate of zero or more — a zero rate simply returns the price unchanged, since multiplying or dividing by one moves nothing — and rejects only a negative one, which has no meaning as a tax added to a price. Everything the two modes report follows mechanically from the single number you enter in the rate field.
Why removing VAT is a division, not a subtraction
The most common error with VAT runs in the remove direction: taking a gross price and subtracting the rate from it, as though adding and removing were mirror operations on the same base. They are not. VAT is charged as a percentage of the net — the smaller, pre-tax figure — so the percentage sitting inside a gross price is a percentage of a number you do not yet have. Dividing by the factor (1 + rate ÷ 100) recovers that net; subtracting the rate from the gross answers a different question and always lands low.
Put numbers on it. A gross of 120 at a fictional 20% rate backs out to a net of 100, carrying 20 of VAT — that is the engine's division. Subtracting 20% straight off the 120 instead gives 96, understating the net by 4. The gap is not fixed; it widens with the rate. Take a gross of 150 at a 50% rate: the correct net is 100 with 50 of VAT, while the subtract-the-rate shortcut returns 75 — now off by 25. The remove mode exists precisely so this division is done the same way every time, at any rate, without the shortcut creeping back in.
The round trip, and why it closes
Adding and removing VAT at the same rate are exact inverses, and the build proves it rather than asserting it. Start from a net of 100: adding 20% produces a gross of 120. Feed that 120 into the remove mode at the same 20% and the net returns to exactly 100, with the same 20 of VAT named both times. Multiplying by (1 + rate ÷ 100) and then dividing by the identical factor cancels cleanly; the only thing that can disturb the round trip is display rounding, covered below, and for everyday prices that stays well out of sight.
This is why the two modes are not redundant. Add mode answers "what will the customer pay?" from a price you set before tax; remove mode answers "what was the price before tax?" from a total that already includes it. The same three figures — net, VAT, gross — describe both, and each mode simply fills in the two you did not start with.
Reading the three figures
Every calculation reports the full trio — net, VAT amount, and gross — because an invoice line in many places is expected to show all three, and because the three together are self-checking. The VAT amount is defined as gross minus net, never rounded on its own, so the parts always reconcile to the whole: net 100 plus VAT 20 is gross 120, exactly. If you ever see a trio that does not add up, it is a display-rounding artifact on a repeating decimal, not an error in the arithmetic.
Decimal rates are handled exactly, not approximated. Adding a fictional 8.875% rate to a net of 250 gives a gross of 272.1875 and VAT of 22.1875 — the engine carries every place the multiplication produces and the display shows them, rather than snapping to the nearest round figure. That matters when a rate has several significant digits: rounding the rate first, or the VAT first, and only then summing is a common source of off-by-a-penny disputes, and defining VAT as the gap between two full-precision numbers sidesteps it.
Decimals, rounding, and what the screen shows
Division rarely lands on a round number, so the remove direction is where rounding becomes visible. Removing 20% from a gross of 100 gives a net of 83.333333 and VAT of 16.666667 — repeating decimals that have no exact finite form. Sumvia's documented policy, set out in full on the methodology page, keeps "the full precision of IEEE-754 double-precision arithmetic" internally, normalizes to twelve significant digits to strip binary artifacts, and on screen rounds "to at most six decimal places." What you read is a clean presentation of a more exact value the engine still holds.
The practical caution is the methodology's own: the figure on screen is the rounded one, so for chained work "prefer doing the whole calculation in one pass" rather than copying a six-decimal net back in as the start of the next step. For a price with two decimal places — the usual case — the rounding is invisible, and the net, VAT, and gross reconcile to the last shown digit.
Where this calculation stops
This page computes one general definition: a single tax charged as a flat percentage of a net price. That is deliberately all it does. It does not know your jurisdiction's rules, and the methodology page states the limit plainly — "tax rules, regulated interest calculations, jurisdiction-specific rounding of currency" are domains that "often impose their own conventions that a generic tool does not know." A real filing may require a particular rounding convention per line or per invoice, may involve reduced or zero rates on part of an order, or may layer taxes so that one is charged on a base that already includes another — none of which a single flat-rate step represents.
The inputs also carry the site-wide range: values are held within a documented ±1015 so results stay where double-precision arithmetic is dependable. And the methodology's broadest caveat applies here as everywhere — "a correct calculation can still be the wrong calculation for your situation." The tool computes the VAT implied by the rate and price you give it; whether that is the right rate, the right base, and the right rounding for your invoice is a judgment it cannot make for you.
Near this calculation
Backing tax out of a gross price is the same divide-by-the-factor move as recovering a price before a percentage increase — the general version lives in the price change calculator. Discounts stack with VAT in the order your invoice applies them; the discount calculator handles that side. And whether a price still clears your costs after tax is a question for the profit margin calculator.
Frequently asked questions
Which rate should I enter?
The one that actually applies to your transaction. VAT (and its relatives like GST) varies by country, by product category, and over time — many countries also run reduced and zero rates alongside the standard one. This calculator deliberately ships no rate table: check the current rate with your tax authority or invoice and type it in.
Why can't I just subtract 20% to remove VAT?
Because the 20% was charged on the net price, not the gross. A gross of 120 at 20% contains 20 of VAT: dividing by 1.2 recovers the true net of 100. Subtracting 20% of 120 would give 96 — an understatement that grows with the rate.
What is the difference between net and gross?
Net is the price before tax; gross is what the customer pays. At a 20% rate, net 100 becomes gross 120, and the 20 between them is the VAT. Invoices in many jurisdictions must show all three, which is why both modes report the full trio.
Does this work for GST and sales tax too?
The arithmetic is identical for any tax charged as a percentage of the net price, so GST amounts and additive sales taxes compute the same way. One caution: some jurisdictions layer multiple taxes or apply tax-on-tax rules, which a single-rate calculation cannot represent.
Can I enter a rate above 100% or with decimals?
Decimals, yes — a rate such as a fictional 8.875% is handled exactly, carried to every place the arithmetic produces. Rates above 100% are also accepted arithmetically (the math is well-defined) even though no VAT regime uses them; the only rejected rate is a negative one.
What exactly is the VAT amount the calculator reports?
It is the difference between gross and net — gross minus net — in both modes, never a separately rounded figure. Adding 100 at 20% gives gross 120, and the reported VAT is the 20 between them. Backing that same 120 out again recovers net 100 and the identical 20 of VAT. The three figures always reconcile because the tax portion is defined as the gap, not computed on its own.
Why do some results show a long row of decimals?
Because division rarely lands on a round number. Removing 20% from a gross of 100 gives a net of 83.333333 and VAT of 16.666667 — repeating decimals the display shows to at most six places, while the engine keeps full internal precision. The figures still reconcile to the gross you entered; what you see is a rounded presentation of a more exact value, as the methodology page documents.
If I apply a discount as well as VAT, does the order matter?
Arithmetically, yes: discounting a net price and then adding VAT is not the same operation as adding VAT and then discounting the gross, and the two routes can land on different totals. This calculator performs one VAT step on the figure you type, so decide which base the discount applies to first and feed this tool the appropriate price. The discount side of that sequence lives in the discount calculator.
Prices are computed locally and never leave your browser. This page performs arithmetic at the rate you supply — it does not know your jurisdiction's rules and is not tax advice; for filings, rely on official guidance. Engine details are on the methodology page.