Set the stake, the price and the commission rate, then choose whether you are backing or laying. The calculator returns your profit if the bet lands, your loss if it does not, and the liability an exchange holds against a lay. Backing risks your stake. A lay risks the stake multiplied by the price minus one, which the exchange ring-fences before kickoff.
Backing and Laying on an Exchange
A back bet is the familiar one: you put up a stake, and if the outcome happens the exchange pays you at the price you took. A lay moves you to the other side of the counter, accepting someone else’s stake and paying them out if the outcome happens, so the bet wins when it fails to happen.
Exchanges match those two sides and charge commission on net winnings rather than shading the price. A bookmaker’s 1X2 market priced 2.50 / 3.40 / 2.90 carries an overround of 3.89%, taken before you bet. An exchange takes its cut after you win, which the Hold / Vig Calculator cannot show you because it is not in the odds.
A Worked Example
£100 at decimal odds of 2.50, exchange commission at 2%.
- Back £100 at 2.50, outcome happens: £150 profit × 0.98 = +£147 after commission.
- Back £100 at 2.50, outcome fails: -£100.
- Lay £100 at 2.50, liability: £100 × (2.50 – 1) = £150 held by the exchange.
- Lay wins, outcome fails: you keep the £100 stake, £100 × 0.98 = +£98.
- Lay loses, outcome happens: -£150.
- Effective odds of that lay: 1 + 100 ÷ 150 = 1.667 before commission.
The final line is the one most people skip past. Laying at 2.50 means risking £150 to win £100, a bet at 1.667 that the outcome does not occur. Read a lay price that way before deciding whether you want it.
Reading Liability and Effective Odds
Liability is the figure to watch: the money the exchange freezes in your account, and the amount that disappears if the bet goes wrong. At 2.50, a £100 lay ties up £150. At 6.00 the same £100 lay ties up £500, and one result takes all of it.
Commission lands on winnings and leaves losses untouched. The winning back gives up £3 of its £150; the winning lay gives up £2 of its £100. The drag falls on the side of the ledger you were counting on, and trading in and out of the same market pays it twice.
Effective odds let you price a lay against backing the opposite outcome somewhere else. A lay at 2.50 is 1.667 on the other side, so a bookmaker showing 1.75 pays more for the same opinion before commission is considered.
Commission Drag and Getting Matched
Two percent on every winner is a running cost that compounds against a thin edge. A back at 2.50 you rated a 5-point edge on returns £147 rather than £150 when it lands, while the losing version still costs the full £100. Across a season of small edges, that gap moves a marginal approach onto the wrong side of breakeven.
Liquidity is the harder problem. Exchange money concentrates on match odds in the big leagues and thins out in the markets and competitions where mispricing is most likely. An offer of 2.50 with £40 behind it is not a 2.50 market for a £100 stake; part of your bet gets matched and the rest sits there until the game starts. Check the money available at the price before you plan around it.
Unmatched money breaks hedging plans too. The Hedge Calculator assumes you can get on at the price you modelled, and an in-play market running away from you between clicks is why the arithmetic in your account differs from the arithmetic on the page.
What the Exchange Price Tells You
An exchange price is the cleanest read on market opinion available, because it carries commission instead of a built-in margin. What it cannot give you is a second opinion to test it against. Gecko Edge builds that for football from Poisson goal models with a Dixon-Coles correction, blended with market and league priors, then measures each price against the model’s own probability across 130+ leagues. The Expected Value Calculator runs the same comparison one bet at a time.
Further Reading
- All betting calculators: the full library of 34 free tools
- Orbit Exchange review: professional exchange betting through a broker
- Integrating in-play betting strategies with real-time EV calculations
What is the difference between backing and laying a bet?
Backing means staking money on an outcome happening, with the exchange paying you at the price if it does. Laying means taking the other side: you accept another bettor’s stake and pay them out if the outcome happens, so the lay wins when it does not. A back risks your stake, a lay risks the liability, and on a £100 bet at 2.50 those are £100 and £150.
How is lay liability calculated?
Liability is the lay stake multiplied by the price minus one. Laying £100 at decimal odds of 2.50 gives £100 × 1.50 = £150, held by the exchange until the market settles. Longer prices swallow more money for the same stake: a £100 lay at 6.00 requires £500 of available funds.
How much commission do betting exchanges charge?
Rates vary by exchange and by market, with 2% used throughout the example on this page. Commission applies to net winnings on a market, so losing bets attract none. A winning £100 back at 2.50 returns £147 of profit rather than £150 once 2% is taken.
Is laying at 2.50 the same as backing at 1.667?
Before commission, yes. Laying £100 at 2.50 means risking £150 to win £100, which matches decimal odds of 1 + 100 ÷ 150 = 1.667 on the outcome failing to happen. Commission shifts it a little, since 2% applies to the £100 you win but not to the £150 you risk.