A Fix-a-Bet is a corrective back bet used to neutralise or reduce the loss from an already-placed exchange lay that you cannot or do not want to cash out.

How does exchange commission affect the fix?

Commission reduces your profit when the selection loses, so it changes the balance point for the corrective back stake.

Is this the same as cashing out?

No. This calculator assumes you are placing a new back bet in the market rather than using an exchange cash-out button.

What if the back odds move?

If the price changes, recalculate with the new odds to get an updated corrective stake.

Fix-a-Bet Calculator

Q: Can I use this for partial matches?

Yes. Add each matched lay as a separate row and the calculator will combine the exposure before solving for the corrective back stake.

Made an exchange mistake? This tool works out the corrective bet needed to neutralise a wrong lay or over-stake when you cannot cash out. It is designed to reduce losses, not generate profit.

Fix wrong lay, over-lay, or partial matches.
See liability and profit/loss for each outcome.
Get the corrective stake to level outcomes.

Tools are informational only, not betting advice, and do not guarantee profit.

Written by Alex Carter · Last reviewed: 16 March 2026

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This calculator is an educational tool for understanding how to correct misplaced exchange bets. It does not provide betting advice, tips, or predictions.

Fix-a-Bet Calculator

Correct a mistaken exchange lay without cashing out.

Exchange recovery

Mode

Bet type

Fix strength (%)

0% = no fix. 100% = level outcomes. Current: 100%

Exchange lay odds (decimal)

Lay stake matched so far (£)

Exchange commission (%)

Advanced: add each matched lay if you were partially matched at multiple odds. When rows are added, the single lay fields are ignored.

Back odds (decimal)

Back commission (%)

This calculator assumes a single selection market and a back bet placed now to offset an existing lay. Enter your exchange lay details, add any partial matches, then set the back price you can get at the moment.

How it works

How the Fix-a-Bet calculation works

Lay outcomes: Win exposure = −(O − 1) × L. Lose profit = L × (1 − c).

Back outcomes: Win profit = (O − 1) × B × (1 − c). Lose loss = −B.

Mode A (level outcomes): solve so win P/L equals lose P/L.

B = (lose_ex − win_ex) ÷ ((O_back − 1) × (1 − c_back) + 1)

Mode B (reduce loss): the stake is an adjustable percentage of the full level-out stake.

Multiple matched lays: sum the lay win/lose exposure for each row, then apply the same formula above.

Always gamble responsibly. This calculator is for information only and does not guarantee profit.

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FAQs

Is this tool meant to generate profit?

No. The goal is to repair an unwanted position and reduce the downside when you cannot cash out.

Why is there a reduce-loss mode?

Sometimes you only want to reduce exposure. The reduce-loss mode uses a smaller stake and shows the new outcomes.

What if my lay was at multiple prices?

Add each matched lay row and the calculator will combine the exposure before solving the fix.

Does back commission matter?

Yes. If your back bet is commissionable, add it so the levelled stake is accurate.

When to use the Fix-a-Bet calculator

Mistakes happen on betting exchanges. You might accidentally lay the wrong selection, enter the wrong stake, or match at the wrong price. The Fix-a-Bet calculator helps you work out the corrective bet needed to neutralise or reduce the impact of a misplaced lay bet. Instead of panicking, you can calculate exactly what opposing bet to place to level out your position.

The calculator offers two modes. "Level outcomes" finds the back stake that equalises your profit and loss across both outcomes, effectively closing the position with a small known cost. "Reduce loss" lets you choose what percentage of the original stake to use for the corrective bet, limiting your maximum downside while leaving some variance in the result.

Detailed worked example

You accidentally laid a selection at odds of 5.0 for a stake of £10 on Betfair (2% commission). Your liability is (5.0 − 1) × £10 = £40.

If the selection loses (lay wins): You profit £10 × (1 − 0.02) = £9.80
If the selection wins (lay loses): You lose £40.00

To level the outcomes, you need to place a corrective back bet on the same selection. The calculator determines the back stake that produces equal profit or loss regardless of the result. If the current back odds are 5.2, the corrective back stake would be approximately £7.55, resulting in a levelled loss of around £2.35 either way — far better than the £40 worst case.

Common mistakes when fixing bets

Waiting too long: The longer you wait, the more the price may move against you. Fix the error as soon as you notice it.
Placing the corrective bet on the wrong selection: The fix must be on the same selection as the original mistake. Double-check before confirming.
Expecting to profit from the fix: The purpose of fixing is damage control, not profit. Accept a small known loss rather than risking a much larger one.
Not checking the current odds: The corrective stake depends on the current market price. Enter the live odds, not the odds from your original bet.

Related guides

Betfair Trading for Beginners — covers the basics of exchange trading, including common errors and how to avoid them.
Back/Lay Hedging Explained — the principles behind hedging apply directly to fixing misplaced bets.
Lay Liability Guide — understand how lay liability works so you can assess the damage from a misplaced lay.