How to Calculate Expected Payout on Betfair

Expected payout tells you how much money you can expect to receive (or lose) from a bet on average, based on the odds and the probability of winning. Understanding this number helps you compare different bets, judge whether a price is fair, and evaluate value opportunities properly.

What Is Expected Payout?

Expected payout is the mathematical average of all possible outcomes weighted by their probability. It is a core concept behind expected value (EV) and is used by professional traders to estimate long-term returns.

In simple terms: expected payout tells you what a bet is “worth” over thousands of repetitions.

Expected Payout Formula

For a back bet:

expectedPayout = (p × profitIfWin) − (q × stake)

where:

p = your estimated probability of winning
q = 1 − p
profitIfWin = (odds − 1) × stake

Working Example

You back a selection at:

Odds: 3.50
Stake: £10
Your estimated win probability: 32%
Commission: 5%

Step 1: Calculate profit if the selection wins

Profit = (£10 × (3.50 − 1)) = £25 Commission of 5% = £1.25 → net win = £23.75

Step 2: Probability of losing

q = 1 − 0.32 = 0.68

Step 3: Expected payout


expectedPayout
= (0.32 × 23.75) − (0.68 × 10)
= 7.60 − 6.80
= +£0.80

This bet has a positive expected payout and is therefore a value bet.

Expected Payout vs Expected Value

Expected payout and expected value are closely related. EV is expected payout expressed as net profit per bet, while expected payout can include stake return depending on definition. Both measure long-term profitability.

How to Calculate Expected Payout for Lay Bets

For lay bets, payout is reversed. Instead of winning profit if your team wins, you win the backer’s stake if the selection loses.

Expected payout formula for lay bets is:

expectedPayout = (q × layStake) − (p × liability)

where:

q = probability the selection loses
p = probability it wins
liability = (layOdds − 1) × layStake

Lay payout becomes especially sensitive when lay odds are high, as liability grows quickly.

Using Expected Payout With the EV Calculator

The easiest way to measure whether your expected payout is positive is to use the EV calculator: Smarter Trades EV Calculator.

It handles:

commission
probabilities
liability
payout calculations

Why Expected Payout Matters

Measuring expected payout helps traders:

avoid negative value bets
compare different betting options properly
identify overlays and underpriced favourites
understand long-term profitability

Frequently Asked Questions

Is expected payout the same as EV?

Related but slightly different. EV is pure profit, expected payout can include stake return. Both are useful decision tools.

Does commission always reduce payout?

Yes. Commission reduces net profit, so expected payout should always include it.

Where can I calculate EV automatically?

Use the Smarter Trades EV Calculator: EV Calculator.