Free Bet Converter

How Free Bet Conversion Works

Free bet conversion is the process of turning a bookmaker's free bet into guaranteed cash profit. By placing a back bet with the free bet at a bookmaker and simultaneously laying the same outcome at a betting exchange, you extract a percentage of the free bet's face value as real money, regardless of the result. This guide explains the mechanics, the formulas, and how to maximise your conversion rate.

Stake Not Returned vs Stake Returned

The most important distinction in free bet conversion is whether the stake is returned on a winning bet. Stake Not Returned (SNR) is the standard type. If your $50 free bet wins at odds of 4.0, you receive $150 profit but the $50 stake is not returned. Stake Returned (SR) free bets return both the profit and the original stake, so the same winning bet would return $200. SR bets convert at close to 100% and are far more valuable, but most bookmaker promotions use SNR. Always check the terms before calculating your lay stake.

What Is Conversion Rate?

The conversion rate is the percentage of the free bet's face value that you extract as guaranteed profit after both bets settle. A $50 free bet with a 78% conversion rate yields $39 in guaranteed profit. The conversion rate depends on the odds you choose and the exchange commission. Higher back odds produce higher conversion rates because the unreturned stake represents a smaller fraction of the total payout.

Optimal Odds Selection

For SNR free bets, targeting back odds of 5.0 to 8.0 typically gives the best balance between high conversion rate and available liquidity at the exchange. Below 3.0, conversion rates drop below 65%, making the free bet less valuable. Above 10.0, conversion rates are excellent (85%+) but exchange liquidity can be thin, meaning your lay bet may not get matched. The sweet spot is usually 5.0-7.0 where you can reliably find close odds on both sides.

The Back-Lay Formulas

For an SNR (stake-not-returned) free bet, the correct lay stake is:

Lay Stake = Free Bet × (Back Odds − 1) / (Lay Odds − Commission)

Note the Back Odds − 1: because the stake isn't returned, you only hedge the winnings. Using full Back Odds in the numerator is the SR (stake-returned) formula (Lay Stake = Free Bet × Back Odds / (Lay Odds − Commission)), and mixing the two is the most common matched-betting mistake. The guaranteed SNR conversion rate is:

Conversion = (Back Odds − 1) × (1 − Commission) / (Lay Odds − Commission)

For example, a $50 SNR free bet at back odds of 6.0, lay odds of 6.2, and 5% commission: Lay stake = (50 × 5.0) / (6.2 − 0.05) = $40.65. If the back bet wins, you collect $250 from the bookmaker and lose $211.38 at the exchange ($40.65 × 5.2), netting $38.62. If the back bet loses, the free bet cost you nothing and you win $38.62 at the exchange ($40.65 × 0.95). The profit is identical either way, which is the point of the hedge, for a 77% conversion. A correct lay always locks the SAME profit on both outcomes; if your two scenarios differ, the stake is wrong.

The calculator above uses these formulas with Commission = 0 (a commission-free exchange), so when the lay wins you collect the full backer's stake. The table below shows the same math with 5% commission.

Conversion Rates at Different Odds

The table below shows typical conversion rates assuming 5% exchange commission and closely matched back/lay odds:

As shown, moving from odds of 3.0 to 10.0 increases conversion by over 20 percentage points. However, the marginal gain decreases at higher odds, and liquidity becomes a constraint. For most free bets under $100, odds in the 5.0-7.0 range offer the best real-world results.

To learn more about the full matched betting workflow, see our matched betting calculator and guide. For converting between odds formats, use the odds converter. And for more complex hedging scenarios involving multiple legs, check the hedge calculator.