Free Betting Tools: Calculate Exchange Commission, Odds and Access
You back a 2.50, the bet wins, and the balance moves by less than the figure in your head. Nobody hid anything: the sums just came after the bet instead of before it.
This page has two live tools and four sums to do by hand. The first tool is the access route finder: five questions in, then the routes into Betfair Exchange that may still be open to you, each with the limit it carries. The second is an overround and fair-odds calculator for the cut inside a set of prices. The sums are commission on a winning exchange bet, back stake against lay liability, the overround of a two-way market and odds turned into probability, each worked with numbers you can check on paper. Rates shown are examples: your own rate depends on your account and region, so check the current terms.
A live tool for access: the route finder
A calculator prices a bet but cannot say whether your account may place it, and a price you cannot reach is only a number. The route finder works on that access side.
It asks five questions, each with a Not sure answer: does Betfair take accounts where you live, what you want within reach from one login, what you bet on most, how often you bet, and whether you bet by hand or with software. It answers with a verdict on the direct route, a count of the brokers that reach every venue you asked for and the three routes (direct, through a broker, not for you). Under each of four brokers, in a fixed order, sit a limit line and a money line. It never rules on your country, and every result closes with the same reminder: check the broker's own country list and the current terms.
It needs no account or email and stores nothing. Use it if you are not sure which route is worth trying, and skip it if you already bet on the exchange and only want the sums. Open the route finder, and when it points you to a direct account, the step-by-step access guide covers the rest.
Every sum on this page fits on the back of a slip.
Sum one: what exchange commission takes from a win
Start with the sum that surprises people most. On an exchange you back at a price, the bet wins, and a percentage of your net winnings on that market goes to the exchange. Losing markets pay nothing. Betfair's terms tie the charge to the market, not the bet, and say your stakes are not relevant.
A worked example
Now add a second bet in the same match odds market: £10 on the draw at 4.00. If your team wins, the draw bet loses £10, so your net winnings on the market are £60 minus £10 = £50, and 5% of £50 is £2.50 rather than £3.00. If the match is drawn instead, the draw bet wins £30, the team bet loses £40, the market nets minus £10, and the exchange takes no commission.
The rate is not one number
The 5% is an example, and so is every rate in these worked examples. Your own rate depends on your account and region, so check the current terms. Betfair's own example for its Basic package is 2%, which turns £100 of net profit into £2.00 of exchange commission; in other regions the rate starts from a market base rate and a discount comes off it.
| Example rate | Where a figure like it appears | Exchange commission | You keep | Effective odds |
|---|---|---|---|---|
| 2% | Betfair's Basic package example | £1.20 | £58.80 | 2.470 |
| 5% | A default market base rate in some countries | £3.00 | £57.00 | 2.425 |
| 6.5% | The default market base rate for all other countries, before any discount | £3.90 | £56.10 | 2.403 |
What a calculator automates: the same steps for any stake, price and rate, netted across every bet in the market. Do it by hand once anyway, because the effective odds decide whether a price is worth taking.
Sum two: back stake against lay liability
Deep breath. The rest is easier.
Backing and laying are mirror images, and the mirror is where money goes missing in your head. When you back, you risk your stake. When you lay, you act as the bookmaker for that bet, so you risk the liability: (odds minus 1) × stake.
Take the same £40 at 2.50 from the other side. Backing wins £60 while risking £40, whereas laying £40 at 2.50 risks (2.50 minus 1) × £40 = £60 to win £40 if the selection loses. At the example 5%, exchange commission on that £40 is £2.00, so you keep £38.00.
The hedge, by hand
Back £40 at 2.50, wait until the price falls to 2.00, then lay £50 at 2.00, and the position locks: if the team wins you collect £60 on the back bet and pay £50 on the lay, if it loses you drop £40 on the back bet and collect £50 on the lay, and either way you finish £10 up before exchange commission.
The £50 comes from back stake × back odds ÷ lay odds, so £40 × 2.50 ÷ 2.00. Both outcomes net £10 on the market, so the example 5% takes £0.50 either way and leaves £9.50.
What a calculator automates: it finds the £50, applies your rate to the result and lays every outcome side by side.
Sum three: the overround of a two-way market
Every set of prices carries a margin, and you can measure it in one line. Turn each decimal price into a probability by dividing 1 by the price, add the results, and compare the total with 100%. A perfectly fair two-way market adds up to exactly 100%, and anything above that is margin.
Illustrative prices: two teams, both at 1.91. Each is 1 ÷ 1.91 = 52.36%, so the pair adds up to about 104.7%, an overround of roughly 4.7 points.
On an exchange the price comes from other customers rather than from a trader protecting a margin, so the same sum on the best back prices can land closer to 100%. Try 1.98 and 2.02, illustrative again: 50.51% + 49.50% = 100.01%. Your cost shows up elsewhere, in the gap between the best price to back and the best price to lay, and in exchange commission on winnings.
What a calculator automates: a whole market at once, as in the overround and fair-odds tool, where by hand you would stop at three or four runners.
Sum four: odds into probability, and what exchange commission does to break-even
Implied probability is 1 ÷ decimal odds, so a 4.00 is 25%, a 2.50 is 40% and a 1.80 is 55.6%. If your screen shows fractions, convert first: 3/2 is 1 + 3 ÷ 2 = 2.50.
Here the earlier sums meet: at 2.50 a bet has to win 40% of the time to break even before charges. After 5% exchange commission the effective odds are 2.425, and 1 ÷ 2.425 = 41.24%. The exchange has raised the bar by about 1.2 percentage points, and no calculator can tell you whether your own estimate clears it.
What a calculator automates: a whole list of prices in one go, in decimal, fractional or American.
Where the sums stop
A calculator assumes your whole bet is matched at the price you typed. On an exchange only the part another customer takes is, and the rest waits unmatched. It also knows neither your available balance nor your exposure limit, and Betfair's maximum bet is the lesser of the two.
Small differences sit outside the formulas too. Betfair's minimum stake is £1 or €1 (check the current terms), broker tools set their own, and amounts round to two decimals, so your statement and your pencil can disagree by a penny.
When the sums say yes and the account says no
Sums are the easy half. Suppose your arithmetic says the exchange is cheaper and your account cannot reach it: the route finder sorts the routes that may still be open, and the access section maps every route into the exchange.
Picture a bettor whose sums say the exchange is cheaper, whose account cannot reach it, and who signs up to a broker's exchange tool on the strength of a headline rate, only to find that the withdrawal fee, the minimum stake and the turnover rule they skimmed past now matter more than the percentage they compared.
That is why the broker's terms come before its rate: the rate becomes the broker's own, and so do the fees around it. Rates, country lists and ID checks all change, so check the current terms before you register anywhere.
Questions people ask
How do I work out Betfair Exchange commission by hand?
Multiply your net winnings on the market by your rate. Betfair's own example for its Basic package is £100 of net profit at 2%, which gives £2.00. Your own rate depends on your account and region, so check the current terms.
What is my liability on a lay bet?
Odds minus 1, multiplied by your stake. Lay £25 at 3.20 and you risk (3.20 minus 1) × £25 = £55.
Which betting calculators do I need, and are they free?
Four jobs cover most exchange bettors: commission on a win, back and lay stakes (including a hedge), the overround, and odds to probability. Those are the four sums on this page, and a calculator only makes them faster. The access route finder is free to use and answers a different question: which route into the exchange fits you.
Where to go next
If the sums convince you and the account is what you need, how sign-up works, from form to first bet is the place to start.