Matched Betting Calculator

This calculator turns an NFL, NBA, MLB, or NHL sportsbook free bet into locked cash by laying it off on a betting exchange, working out the lay stake, the liability, and the guaranteed profit in dollars from American odds like +250 and +260.

What Is Matched Betting?

Matched betting extracts the cash value out of a sportsbook’s free or bonus bet by covering it on a betting exchange. You place the free bet on a selection at one book, then lay the same selection — bet on it to lose — on an exchange, sizing the lay so you end up with roughly the same amount either way.

The sportsbook’s promotion is what makes the whole thing profitable. Lay off a normal, cash bet and all you get back is your own stake minus the exchange’s commission — no value created, just moved around. A free bet is different: there is no stake of your own at risk, so the lay locks in real, withdrawable money that came from the book’s promotion rather than your pocket.

Matched betting is less common in the United States than in the United Kingdom, mainly because betting exchanges are still limited across US markets. Where an exchange is available, the mechanics are identical: back the free bet at one price, lay it at another, and size the lay so the outcome is locked in either way. This calculator does that sizing, showing the lay stake, liability, and locked profit before you place a cent on the exchange.

How Matched Betting Is Calculated

For a stake-not-returned free bet, the lay stake equals the back stake multiplied by the back decimal odds minus 1, divided by the lay decimal odds minus the commission: lay stake = back stake × (back decimal − 1) / (lay decimal − commission). The liability — what you would owe the exchange if the laid bet wins — equals the lay stake multiplied by the lay decimal odds minus 1.

American odds convert to decimal by dividing the plus odds by 100 and adding 1. Odds of +250 become 250 / 100 + 1, or 3.50 in decimal; odds of +260 become 260 / 100 + 1, or 3.60 in decimal.

Once both prices are in decimal form, the commission is folded into the lay side of the equation, since that is the side where real cash is staked and takes the exchange’s cut; the back side needs no such adjustment, because a free bet’s winnings are the book’s money, not yours.

The formula sizes the lay stake so the locked profit comes out the same regardless of which way the game goes: if the back bet wins, profit is the free bet’s winnings minus the liability paid to the exchange; if it loses, profit is the lay bet’s winnings after commission is deducted. Both outcomes converge on the same locked profit — the whole point of matching a free bet.

What the Calculator Shows You

Enter the free-bet amount, the back odds at the sportsbook, and the lay odds and commission at the exchange, and the calculator returns four figures. The lay stake is how much to bet on the exchange to cover the free bet. The liability is what you would owe the exchange if that lay bet wins — money you need available before placing it. The locked profit is what you end up with either way, once the free bet’s winnings or the exchange payout are netted against the liability or commission. Alongside the dollar profit, the calculator shows the retention percentage: how much of the original free-bet amount you converted into cash. Together, these four numbers let you check the trade before committing any money to the exchange side of the bet.

Worked Example

Take a $40 free bet, stake not returned, placed at +250 at the sportsbook. You lay the same selection at +260 on an exchange that charges 2% commission.

Converting to decimal odds, +250 is 3.50 and +260 is 3.60. Plugging those into the formula gives a lay stake of $27.93 — how much you bet on the exchange against the same selection winning. The liability on that lay bet is $72.63, what you would owe the exchange if the selection you backed for free actually wins.

Now check both outcomes. If the back bet wins, the free bet pays out at +250 on a $40 stake, and that amount minus the $72.63 liability leaves a profit of $27.37. If the back bet loses, the lay bet wins on the exchange, and after 2% commission is taken out, the profit is also $27.37. Either way, you clear $27.37.

That $27.37 is roughly 68% of the original $40 free bet — the retention percentage the calculator reports for this trade. The gap between backing at +250 and laying at +260, plus the 2% commission on the exchange side, is what stops you keeping the entire $40; a free bet with no gap and no commission would convert closer to the full amount. Running the numbers first tells you the lay stake and liability you need ready on the exchange before any money moves.

Free-Bet Retention by Odds Gap

The gap between the back price and the lay price changes how much of a free bet you keep, even with the stake and commission held fixed. The table below holds a $40 stake-not-returned free bet backed at +250 and shows what happens as the lay price drifts from +250 out to +280, with commission fixed at 2%. As the gap widens, the lay stake shrinks slightly, the liability climbs, and the locked profit falls.

Back and Lay Odds in Each Format

The back and lay prices from the worked example look different depending on which odds format you read them in. The table below lines up the American price, the decimal price, and the implied probability for both the sportsbook’s back price and the exchange’s lay price, so you can see how a few points of American odds translate into decimal terms.

What Affects Your Locked Profit

Two things move the profit you actually lock in on a free bet: the gap between the back and lay prices, and the exchange’s commission rate. The closer the lay price sits to the back price, the more of the free bet’s value survives the trade, which is why matched betting works best on short-priced, liquid markets rather than long-shot selections with thin exchange volume — a wide gap on an illiquid selection quietly eats into the value before commission is even factored in. Commission works the same way in the background: a 2% exchange leaves more locked profit on the table than a 5% exchange would, for an otherwise identical back and lay price, so the rate is worth checking before choosing where to lay.

It also matters what kind of promotion you are working with: a stake-returned free bet uses a different lay formula than a stake-not-returned one and retains a noticeably higher share of its value, so applying the wrong formula to the wrong promotion type misstates both the lay stake and the liability. The 68% figure in the worked example above assumes the common stake-not-returned kind.

The practical snag in US markets is liquidity. Betting exchanges here carry thinner order books than in markets like the UK, which can mean the full lay stake is not available to match, leaving part of the free bet’s value uncovered simply because nobody was on the other side to take it.

When Matched Betting Makes Sense

Matched betting makes the most sense when a sportsbook offers a free or bonus bet and a betting exchange is actually available to lay it off on. Without an exchange, there is nothing to lay against, and the free bet becomes an ordinary bet with ordinary risk. Where an exchange exists, the appeal is that the outcome is locked in before either leg settles — you are not betting on the game, you are converting a promotion into cash.

Bankroll matters more than it looks like it should, because the liability on the lay side is real money you need available, not free-bet money. In the worked example, laying $27.93 at +260 carries a $72.63 liability that has to sit in your exchange account regardless of how the free bet resolves. Sizing free bets against what you can actually cover on the exchange side keeps the trade from becoming a cash-flow problem even when the profit is guaranteed.

It also makes more sense on liquid, closely matched prices than on long-shot or thin markets, since a wide gap between the back and lay price — or a market where the full lay stake cannot be matched — erodes the value being extracted. If the odds gap or commission on offer would leave only a small share of the free bet retained, it may be worth weighing that against simply using the free bet without laying it off.

Common Mistakes

Laying at odds much higher than the back price bleeds value out of the free bet before commission even applies. Ignoring the exchange’s commission rate overstates the locked profit you walk away with. Using the free-bet lay formula on an ordinary qualifying bet, or vice versa, produces the wrong lay stake and liability. Assuming the full lay stake will be matched in a thin exchange market can leave part of the free bet’s value uncovered.

Matched Betting vs Qualifying Bets

A qualifying bet risks your own cash to unlock a promotion, so the best realistic outcome is close to break-even once laid off. A free bet risks the book’s money instead, which turns the same laying process into locked profit rather than a wash.