Betting margin calculator
Enter every price in a market and see the bookmaker's cut — plus the fair line hiding underneath it.
The market
Add an outcome for three-way markets, or more for outright markets.
What the book is charging
Fair line, margin removed
The margin is what you pay for the right to have an opinion. Two books, the same match, and the difference is money.
The margin is the price of the bet
A fair two-way market prices both sides at 2.00. The implied probabilities are 50% and 50%, they add to exactly 100%, and neither side has an edge. Real markets are priced 1.90 and 1.90: those implied probabilities are 52.63% each, they add to 105.26%, and the excess 5.26 points are the bookmaker's margin — the overround. Whichever side you back, you are paying it. Margins swing hard by market: main lines at sharp books can sit under 2%, while outrights and player props routinely carry 8% or more, because that is where books know their prices are least tested.
Removing the margin gives the fair line, the no-vig line. This calculator does it proportionally — each implied probability divided by their sum, so they add back to exactly 100% — and that fair line is the reference point for every +EV decision: a bet is only positive expected value if your probability beats the fair one, not merely the priced one. One honest limit: real books load more margin onto long shots, so on a market with a heavy favourite this method understates the favourite slightly. On balanced main lines the distortion is small; on lottery-ticket outrights, treat the fair line as an estimate.
The same match at two books
- Recreational book
- 1.90 / 1.90 · margin 5.26%
- Sharp book
- 1.98 / 1.98 · margin 1.01%
- Fair line, both
- 2.00 / 2.00 · 50% each
- Your EV on a true 50% shot
- −5% vs −1% per bet
Identical opinion, identical match. Staking 100 two hundred times costs 1,000 at the first book and 200 at the second: the eight cents of price difference is 800 across a season. This is the cheapest edge in betting and it requires no model at all.
Questions
What margin should I accept?
For main football and tennis lines, under 3% is sharp, 4–5% is normal at a recreational book, and above 7% means you are paying a lot for the privilege of having an opinion. Compare the same market across books before you decide.
Is payout percentage the same as margin?
They are two views of the same number. A 5.26% margin corresponds to a 95% payout: the book expects to return 95 of every 100 staked across the whole market. Payout is the friendlier number to compare between books.
Why do the fair probabilities add up to exactly 100%?
Because that is the definition of removing the margin. The priced probabilities add to more than 100%; dividing each one by that total rescales them so they sum to one, which is what a coherent set of probabilities must do.
Can I use this on a three-way or outright market?
Yes — add as many outcomes as the market has. The maths is identical for any number of outcomes, as long as you enter every one of them. Leaving one out understates the margin.
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