Sports
Betting Odds Explained: Decimal and Probability
Quick Summary
- Decimal odds multiply your stake to give the total return.
- Implied probability is one divided by the odds.
- Add the implied probabilities of every outcome and the excess is the margin.
- This page uses invented example prices to show the sums.
- 18+ only
- Independent guide
- Checked 7 Nov 2026
- Know your limit
Odds are a price, and you cannot judge a price without a little arithmetic. The good news is that it takes one division and one addition. Below we work three examples with made-up numbers, so you can see what the maths does. These are teaching figures, not BDBAJEE prices, and we have not recorded any of its odds.
Decimal odds in one line
A decimal price shows the total return per unit staked, including the stake. At odds of 2.00, a stake of ৳100 returns ৳200 if it wins, which is ৳100 of profit. At 1.50, a ৳100 stake returns ৳150. At 4.00, it returns ৳400.
Many books let you change the display format between decimal, fractional and others. Check that you are reading the format you think you are, since a fraction like 3/1 and a decimal 3.00 are not the same.
From odds to probability
Divide one by the decimal odds. At 2.00 the implied probability is 50 per cent. At 4.00 it is 25 per cent. At 1.25 it is 80 per cent. This is the chance the book is pricing in, margin included. If you think the real chance is higher, the bet may be good value; if lower, it is not.
| Decimal odds | Implied probability | Return on ৳100 stake |
|---|---|---|
| 1.25 | 80% | ৳125 |
| 2.00 | 50% | ৳200 |
| 4.00 | 25% | ৳400 |
Finding the margin
Take a two-way match priced at 1.90 each. One divided by 1.90 is about 52.6 per cent. Add both sides and you get roughly 105.3 per cent. The extra 5.3 per cent over 100 is the book's margin. A fair coin would pay 2.00 each. Margins are higher on props, scorer markets and accumulators, where they stack up leg by leg.
This is why accumulators look generous and lose more than they should. Each leg carries a margin, and the margin compounds. See football betting for how legs stack and cricket odds for cricket examples.
Using the sums honestly
Odds maths does not tell you who wins. It tells you what the price implies, which helps you avoid bad prices. It also shows why no one can promise a profit from betting.
Back to the sports betting hub for market types, and read responsible gaming before you stake.
In three steps
Convert odds in 3 steps
- 1Take the decimal odds
Write down the price shown on the slip, for example 2.50.
- 2Divide one by it
One divided by 2.50 is 0.40, which is 40 per cent.
- 3Compare with your view
If you think the true chance is below 40 per cent, skip the bet.