Is matched betting risk-free?

The maths is, as long as you place both sides at the prices you entered. The risks are human ones: a typo in the stake, odds moving before you lay, or a bookie restricting your account.

Stake not returned. When an SNR free bet wins you get only the winnings, not the free bet stake itself, which is why you lay less against it.

Why do I lose money on the qualifying bet?

The lay odds are almost always a bit higher than the back odds, and the exchange takes commission. A small loss there is what unlocks the free bet.

How much money do I need in the exchange?

At least the liability. It's shown above, and it grows fast at higher lay odds.

Matched Betting Calculator

Back and lay

Currency

Bet type

Back stake (£)

Back odds (bookie)

Lay odds (exchange)

Exchange commission (%)

What you'll make

Lay stake–

Liability (needed in the exchange)–

If the bookie bet wins–

If the exchange bet wins–

Result as % of back stake–

Back/lay rating–

Qualifying / stake returned: lay stake = back stake × back odds ÷ (lay odds − commission). Stake not returned: lay stake = back stake × (back odds − 1) ÷ (lay odds − commission).

A matched betting calculator answers one question: how much do I lay at the exchange so I come out the same whichever way it goes? Get that number wrong by a few quid and the “risk-free” part disappears.

Say a bookie offers a £10 free bet if you bet £10 first. You back a horse at 3.2 and lay it at 3.3 on an exchange charging 2%. The calculator says lay £9.76, with £22.44 liability. Win or lose, you’re down 44p. That’s the qualifying loss, and it’s the price of the free bet.

Then the free bet. £10 stake not returned, back at 5.0, lay at 5.2. Lay £7.72, liability £32.43, and you lock in £7.57 whatever happens. Seven quid for twenty minutes of clicking.

Using the matched betting calculator

Qualifying bet: your own money, both stakes count.
Free bet (stake not returned): the most common type, “SNR”. You only get the winnings.
Free bet (stake returned): rarer and better. Treat it like cash.

Back odds are the bookie’s price. Lay odds are the exchange price you’ll actually get, so check it’s still there. Commission is the exchange’s cut of your winnings there. Betfair’s standard UK rate is 5% and Smarkets is 2%, but check your own account.

What makes a good match

The back/lay rating is back odds divided by lay odds. The closer to 100%, the less you lose on qualifiers. With free bets, though, the price matters more than the rating. An SNR free bet at 2.0 keeps under half its value (£4.85 of £10). At 8.0 you keep about £8.19. Higher odds mean more liability, so you need the cash in the exchange to cover it.

Above 75% retention on an SNR free bet is a good conversion. Under 65% and it’s usually worth finding a bigger price.

The formulas

Qualifying / SR:  lay stake = back stake × back odds ÷ (lay odds − commission)
Free bet SNR:     lay stake = back stake × (back odds − 1) ÷ (lay odds − commission)
Liability       = lay stake × (lay odds − 1)

Commission goes in as a decimal (2% = 0.02). The lay calculator is handy when you only want the liability on a single lay bet.

One honest warning. Bookies don’t like matched bettors, and accounts that only take offers tend to get limited. Treat it as a side thing, not a salary.