How to read the results
- Lay is the stake you enter at the exchange. Lay odds go in exactly as shown on the exchange.
- Liability is what you'd pay out at the exchange if the bookie bet wins. It has to be sitting in your exchange account first.
- Bookie / Exchange / Net shows what each side does in each outcome. In a balanced lay, the two Net figures match.
- The yellow line says it in plain English: the qualifying loss, or the profit you've locked in.
Qualifying bets vs free bets
Every sign-up offer has two halves. The qualifying bet is your own money. You back and lay it to unlock the offer, and it usually costs a few pence. The free bet is where the profit is. You back it with the bookie's money and lay it to lock in most of its value.
| Bet type | Lay stake formula | If the back bet loses |
|---|---|---|
| Qualifying | B × Ob ÷ (Ol − c) | You lose your stake B, the lay wins |
| Free bet (SNR) | B × (Ob − 1) ÷ (Ol − c) | Nothing lost: it wasn't your money |
| Free bet (SR) | B × Ob ÷ (Ol − c) | Nothing lost |
| Refund if loses | (B × Ob − R × r) ÷ (Ol − c) | You lose B but get refund R, worth about r of its value |
Worked example: a whole "bet £10, get £10" offer
- Work out the qualifying bet. Enter back stake £10, back odds 3.0, lay odds 3.1 and commission 2% with Qualifying bet selected.
- Lay at the exchange. Lay £9.74 at 3.1. Liability is £20.45. Your qualifying loss is 45p whatever happens.
- Collect the free bet. When the qualifying bet settles, the bookmaker credits the free bet, for example £10 stake not returned.
- Lay the free bet. Switch to Free bet (SNR). Back £10 free at 5.0, lay at 5.2 with 2% commission: lay £7.72, liability £32.43, locked-in profit £7.57.
- Add it up. £7.57 from the free bet minus 45p qualifying loss = £7.12 profit from the offer, whatever the results.
Underlay and overlay
The slider moves your lay up to 20% either side of balanced. Underlay the £10 qualifying bet at 3.0/3.1 (2% commission) by 10% and you get +£1.59 if the bookie bet wins, −£1.41 if it loses, instead of −45p either way. That's no longer matched betting. It's a small bet, so only do it when an offer gives you a reason to.
Commission, and why 0% deals matter
Commission is the exchange's cut of your winning lays, and it's the biggest thing you control. Same £10 qualifying bet at 3.0/3.1:
| Commission | Lay stake | Qualifying loss |
|---|---|---|
| 0% | £9.68 | 32p |
| 2% | £9.74 | 45p |
| 5% | £9.84 | 66p |
The commission box takes "2", "2%" or "0.02", and remembers what you used last time on this device.
Beginner mistakes the calculator catches
Three it checks for every time:
- Not enough in the exchange. Open "Exchange balance check" and it warns you before your lay half-matches.
- Mixing up SNR and qualifying. The bet type changes the formula. Lay a free bet as a qualifying bet and you'll over-lay it.
- Chasing a bad match. If the lay odds are more than 10% above the back odds, it tells you.
FAQs
What is the matched betting lay stake formula?
For a qualifying bet: lay stake = back stake × back odds ÷ (lay odds − commission). For a stake-not-returned free bet: lay stake = free bet × (back odds − 1) ÷ (lay odds − commission). Commission is a decimal, so 2% is 0.02.
What is a qualifying loss?
The small amount you lose on the bet that unlocks an offer, because the lay odds are usually a bit higher than the back odds and the exchange takes commission. £10 at 3.0 back and 3.1 lay with 5% commission costs 66p either way.
What is liability?
What you pay out at the exchange if your lay loses, which happens when the bookie bet wins. Liability = lay stake × (lay odds − 1). It must be in your exchange account before the lay will match.
Why does commission matter so much?
It comes off every winning lay. The same £10 qualifying bet at 3.0/3.1 costs 32p at 0% commission, 45p at 2% and 66p at 5%. Over hundreds of bets that adds up.
Should I ever underlay or overlay?
Only when you mean to. Underlaying a qualifying bet means you win a bit if the bookie bet wins and lose more if it loses. It’s a small bet on the outcome, which some offers (like ones that pay out early) make worthwhile.
How does the refund-if-loses option work?
If the bookie refunds your stake as a free bet when it loses, that refund is worth roughly 70–80% of its face value once you lock it in. The calculator lays a bit less so both outcomes come out equal, counting the refund at the retention you enter.
Is matched betting legal in the UK?
Yes. You are using offers exactly as bookmakers publish them. Bookmakers can and do restrict accounts that only take offers, which is known as gubbing.
Lewis's take
Between 2017 and 2020 I made about £50,000 from bookmaker offers, and it all started here: qualifying bets, free bets, lay, repeat. Bet365's 2-up promo was a tremendous earner before they gubbed me, and nearly every bookie did in the end. Matched betting is what builds your float. That float is what lets you ride the swings on the +EV stuff later.
Where next
- Free bet calculator: what a free bet returns, and how much you keep.
- OddsMonkey review: the paid tools, priced up honestly.
- Coming soon: dutching calculator, OddsMonkey vs Outplayed, and a guide to gubbing.
Update log
- Calculator launched with qualifying, SNR, SR and refund modes. Formulas unit-tested.