A matched betting calculator tells you exactly how much to lay at a betting exchange to cover a back bet at a bookmaker, so your profit is the same regardless of the outcome. Enter your back stake, back odds, lay odds and commission rate, and the calculator does the rest.
The calculator handles four bet types: qualifying bets, SNR free bets (stake not returned), SR free bets (stake returned), and money back offers. Each type uses a different formula, which is why getting this right manually is error-prone.
How to Calculate Your Lay Stake
- 1Select bet type — Qualifying Bet, Free Bet SNR, Free Bet SR, or Money Back. Each type changes the formula.
- 2Enter back stake and back odds — the amount and odds at the bookmaker. Example: €20 at 3.50.
- 3Enter lay odds and commission — the exchange lay price and your commission rate. BFB247 charges 2.5%; Betfair charges 5%.
- 4Read the results — the calculator shows your lay stake, liability, and profit or qualifying loss across all outcomes.
The Lay Stake Formulas Explained
Each bet type uses a different formula. Here is the maths behind what the calculator computes:
Qualifying bet
Lay stake = (Back odds × Back stake) ÷ (Lay odds − Commission)
Example: Back €20 at 3.50, lay at 3.60 with 2.5% commission → Lay = (3.50 × 20) ÷ (3.60 − 0.025) = €19.58
SNR free bet (stake not returned)
Lay stake = ((Back odds − 1) × Free bet) ÷ (Lay odds − Commission)
A €20 SNR free bet at 3.50 back, 3.60 lay, 2.5% commission → €13.93 lay stake, ~€16.70 profit
SR free bet (stake returned)
Lay stake = (Back odds × Free bet) ÷ (Lay odds − Commission)
Money back offer
Lay stake = (Back odds × Stake − Cashback) ÷ (Lay odds − Commission)
Qualifying Loss vs Free Bet Profit: What the Numbers Mean
A qualifying bet will almost always show a small negative result, typically 2–4% of your stake. That is expected and intentional. You accept a small qualifying loss to unlock a free bet worth far more.
A €20 qualifying bet at odds of 3.50 with a 3.55 lay and 5% commission produces a qualifying loss of roughly €0.80. The €20 SNR free bet that follows converts to around €16 in cash. Net result: approximately €15.20 guaranteed profit from one offer.
Lower commission directly reduces qualifying loss on every bet. This is why BFB247 at 2.5% saves meaningfully over Betfair at 5% for high-volume matched bettors.
Common Mistakes When Using a Matched Betting Calculator
- ✕Using the wrong bet type. Selecting "qualifying bet" when you have an SNR free bet will give you a completely wrong lay stake. Always confirm which type the promotion is before entering values.
- ✕Ignoring commission. Entering 0% commission when your exchange charges 5% means the lay stake is too low and one outcome loses money. Always enter your actual rate.
- ✕Using back odds instead of lay odds from the exchange. The back price and lay price on an exchange are different. The lay price is always higher than the back price for the same selection.
- ✕Not checking exchange liquidity. If the exchange does not have enough money available to match your full lay stake at those odds, you cannot complete the trade at the calculated price.
Frequently Asked Questions
What is a matched betting calculator used for?
It calculates the exact lay stake needed to cover a back bet, so the profit from a bookmaker free bet or promotion is guaranteed regardless of which outcome wins or loses. Without it, you are guessing, and guessing costs money.
What is a qualifying loss and how do I minimise it?
A qualifying loss is the small deficit from the qualifying bet placed to unlock a free bet. Typically 2–5% of the back stake. Minimise it by finding back and lay odds as close together as possible, and by using a lower commission exchange like BFB247 at 2.5% instead of Betfair's 5%.
What is the difference between SNR and SR free bets?
SNR (Stake Not Returned) means only the winnings are paid, not the original stake. SR (Stake Returned) means you get the stake back as well. An SNR free bet is worth roughly 75–85% of face value when converted to cash; an SR bet is worth around 95%. The calculator handles both formulas automatically.
Can I use this calculator for any bookmaker?
Yes. The calculator works for any bookmaker and any exchange. Simply enter the odds and commission rate that apply to your specific accounts. For finding the best available lay odds across exchanges, use the Oddsmatcher.
What does underlay and overlay mean?
Underlay means laying less than the calculated optimal stake, so you profit more if the back bet wins but less if it loses. Overlay is the opposite. Both shift profit between outcomes. For most matched betting scenarios, the balanced calculation is correct.
Ready to put these calculations into practice? The matched betting guide walks through the full process from sign-up offer to ongoing profits, and the Oddsmatcher finds the best lay odds automatically.