Almost every free bet has to be earned by placing a real one first. That bet is made with your own money, so the stake comes back whether it wins or loses — which changes the arithmetic, and means the sensible goal is not profit but a small, known loss.
Use the calculator on the free bet calculator page and switch the type to stake returned. The formula changes to:
S = F × B ÷ (L − c)
and the result is your qualifying loss.
What a normal qualifying loss looks like
A well-matched qualifying bet at short odds usually costs somewhere in the region of a few percent of the stake. The closer the lay odds sit to the back odds, the smaller it is.
This is why qualifying bets are placed at short odds while free bets are placed at long ones. At short prices the gap between back and lay is naturally tighter in absolute terms, so the loss is small. On a stake-not-returned free bet the incentive runs the other way, because the proportion kept rises with the price.
The order of operations
- Read the terms first — minimum odds, minimum stake, qualifying window, and what actually triggers the free bet.
- Place the qualifying bet at odds that satisfy the terms, matched as tightly as you can.
- Lay it at the exchange for the stake the calculator gives.
- Wait for settlement. The free bet usually arrives after the qualifying bet settles, not after it is placed.
- Use the free bet at longer odds, with the calculator set to stake not returned.
Where this goes wrong
Placing at odds below the minimum. The bet qualifies for nothing and you have taken a loss for no reason.
Laying before the back bet is confirmed. If the bookmaker voids or rejects the bet you are left with an unmatched exchange position.
Assuming the free bet is one piece. Plenty are split — four £5 bets rather than one £20 — which changes the odds you would sensibly use and multiplies the work.
Forgetting the expiry. A free bet you never place is worth precisely nothing.