Implied Probability Explained

The formula, step by step

Every decimal price on the AFL, NRL, Big Bash, A-League or a Saturday race meeting can be turned into a percentage the same way.

• Take the decimal odds.
• Divide 1 by that number.
• Multiply by 100 to get a percentage.

Worked examples:

• $1.50 → 1 ÷ 1.50 = 0.667 → 66.7%
• $2.50 → 1 ÷ 2.50 = 0.400 → 40.0%
• $3.20 → 1 ÷ 3.20 = 0.313 → 31.3%
• $6.00 → 1 ÷ 6.00 = 0.167 → 16.7%
• $11.00 → 1 ÷ 11.00 = 0.091 → 9.1%

Shorter odds = higher implied probability (bigger favourite). Longer odds = lower implied probability (bigger roughie). The number you get is the break-even win rate: a $2.50 shot needs to win 40% of the time just for you to come out level over the long run.

Why the percentages add up to more than 100%

Add the implied probabilities for every runner or team in a market and you won't get 100% — you'll get more. That extra chunk is the bookmaker's margin (also called the overround or the vig). It's how the operator builds a profit into the price.

Take a two-way market like an NRL head-to-head:

• Team A at $1.80 → 55.6%
• Team B at $2.00 → 50.0%
• Total = 105.6%

The 5.6% above 100% is the margin. A true 50/50 game with no margin would be priced $2.00 each side (50% + 50% = 100%). The tighter the total is to 100%, the sharper the odds and the better value for you.

To get the 'true' chance the bookie is implying, divide each outcome's implied probability by the market total. For Team A: 55.6 ÷ 105.6 = 52.7%. That's the margin-adjusted, fair estimate.

Margins vary by bookmaker — and the data shows it

The size of the margin is the practical reason implied probability matters. Two bookies can price the same match differently, and the one with the lower margin is quietly handing you a better implied probability on the same selection.

Across BETAURO's sampled price data, average margins ranged noticeably between operators:

• Sportsbet — ~4.9% average margin (44 markets sampled), the tightest in the sample
• PointsBet — ~5.6% (51 sampled)
• Ladbrokes — ~5.8% (258 sampled)
• Unibet — ~5.8% (243 sampled)
• Neds — ~5.9% (59 sampled)
• PlayUp — ~5.9% (44 sampled)
• TAB — ~6.0% (59 sampled)
• betr — ~6.2% (56 sampled)
• bet365 — ~7.4% (30 sampled)

Lower margin means the totalled implied probabilities sit closer to 100%, so more of the true price is passed back to you. This is editorial judgement based on the sampled data — margins move constantly by sport, market and event, and a 30-market sample (bet365) is smaller than a 258-market one (Ladbrokes), so treat these as directional, not fixed. Compare live prices before you bet using our betting odds pages.

Using implied probability to find value

Value betting means backing a price whose implied probability is lower than the real chance of the outcome. If you think a team wins 50% of the time but the bookie prices it at $2.50 (40% implied), the price is generous — you're getting paid as if it's less likely than you believe.

A quick decision rule:

• Convert the odds to implied probability.
• Compare it to your own honest estimate of the chance.
• If your estimate is higher than the implied figure, there's value. If it's lower, walk away.

Worked value example: Sydney to beat Melbourne in an AFL clash is priced at $3.00. Implied probability = 1 ÷ 3.00 = 33.3%. Suppose your form read, ground advantage and injury news suggest Sydney win closer to 40% of the time. Since 40% > 33.3%, the price offers value on your read.

Expected value on a $50 stake: at $3.00, a win returns $150 ($100 profit). Over 100 identical bets at a true 40% win rate you'd win 40 times: 40 × $100 profit = $4,000, minus 60 losses × $50 = $3,000. Net +$1,000, or +$10 per bet. The edge exists only if your 40% estimate is right — implied probability tells you the break-even, but your own judgement decides whether there's value above it.

Converting odds fast at the track and on the app

You don't need a calculator for a rough read. Handy anchors to memorise:

• Even money ($2.00) = 50%
• $1.50 ≈ 67%
• $1.33 ≈ 75%
• $3.00 ≈ 33%
• $4.00 = 25%
• $5.00 = 20%
• $10.00 = 10%
• $21.00 ≈ 4.8%

For multi-runner markets like a horse race field, add up the implied probabilities of the runners you're weighing. If the favourite at $2.20 (45.5%) and second-pick at $4.50 (22.2%) already total 67.7%, the rest of the field is sharing roughly a third of the market once you subtract, with the margin baked in on top. This is where longer fields carry fatter overrounds — more runners, more margin.

Most Australian betting apps display decimal odds by default, so the 1 ÷ odds conversion works everywhere. If you switch to fractional or American formats, convert back to decimal first, then apply the same formula.

Where implied probability doesn't tell the whole story

Implied probability is a snapshot of the price, not a guarantee. Keep three limits in mind:

• It includes the margin, so the raw figure overstates the bookie's true belief. Always adjust by the market total for a fair estimate.
• Prices move. A market mover shortening from $3.00 to $2.40 has lifted its implied probability from 33% to 42% as money and information arrive. Track shifts on our market movers page.
• It's only as good as your counter-estimate. Converting odds is arithmetic; judging whether the true chance is higher is the hard part, and that's where research, form and discipline earn their keep.

Use implied probability as a filter, not an oracle: it stops you backing prices that can't be profitable long-term and highlights where your own read disagrees with the market.