Betting odds explained
Decimal odds, implied probability, and the margin that sits inside every price. Four calculations, all of which you can do on a phone, and which together explain most of what a betting site is doing to your money.
Updated · The Natybet Desk
Kenyan betting sites show decimal odds. Multiply your stake by the odds to get your total return, which includes your stake back: KES 100 at 2.50 returns KES 250. Divide 1 by the odds to get the probability the price implies: 1 ÷ 2.50 = 0.40, so that price is claiming a 40% chance. Those two sums are the whole of odds arithmetic, and doing the second one is what turns a price from a number into a claim you can argue with.
Add up the implied probabilities of every outcome in a match and you will get more than 100%. The excess — typically five to ten percentage points on a Kenyan football market — is the operator's margin. It is charged on every bet, win or lose, and it is the reason a bettor who picks outcomes exactly as well as the market still finishes the year down.
The four sums
- Total return
- Stake × odds
- Profit
- Stake × (odds − 1)
- Implied probability
- 1 ÷ odds
- Accumulator odds
- Odds₁ × odds₂ × odds₃ …
Reading a decimal price
A decimal price is a multiplier on your stake, and it already contains your stake. This trips up almost everyone once: at odds of 1.90, staking KES 500 returns KES 950, of which KES 450 is profit. The app will usually show both figures, labelled something like “potential win” and “total payout” — read which one you are looking at before you decide a bet is worth placing.
Anything below 2.00 is an odds-on price: you are risking more than you stand to profit. Anything above 2.00 is odds-against. Exactly 2.00 is an even-money bet, where profit equals stake.
Implied probability, and why it is the useful one
Dividing 1 by the odds converts the price into the market's stated opinion about how often that outcome happens. This is the number to argue with, because “1.65 feels short” is a vibe, while “that price says this team wins 61% of the time and I think it is closer to 50%” is a position you can be right or wrong about.
- 1.20 implies 83.3% — expect it to lose roughly one time in six.
- 1.50 implies 66.7% — one loss in three.
- 2.00 implies 50% — a coin flip.
- 3.50 implies 28.6% — expect it to lose about five times in seven.
- 10.00 implies 10% — nine losses for every win, if the price is right.
Notice what that last line does to a strategy built on big prices. A 10.00 shot losing eight times running is not bad luck and not a sign the book is rigged. It is the ordinary behaviour of a 10% event, and it is also the point at which most people start chasing.
Finding the margin
Take a match priced 2.10 / 3.40 / 3.60 for home, draw and away. The implied probabilities are 47.6%, 29.4% and 27.8%. They total 104.8%. That 4.8% is the operator's margin on this market — the amount by which the prices are collectively shorter than the real probabilities can be.
Two things follow. First, comparing that total across operators is the only genuinely objective way to say which one is offering better prices, and it is far more informative than any bonus. Second, the margin compounds across an accumulator: a five-leg multi built from markets with 5% margins is carrying roughly 25% of margin in total, which is why long accumulators are the most profitable product a bookmaker sells. We do that arithmetic in full on the multibet page.
Where margin is widest
Margins are not uniform. They are tightest on the biggest markets — the match result in a major league, where competition between operators is fiercest — and widest on the markets designed to look exciting: correct score, first goalscorer, half-time/full-time doubles, and anything involving a long list of possible outcomes. If you cannot see the margin, assume it is large.
The same logic applies to jackpots and to crash games. A 17-game jackpot is a market with 129 million outcomes, priced by a prize pool rather than by odds; the arithmetic is on its own page. Aviator's margin is built into the distribution of crash points rather than into a price, which we explain at Aviator RTP and house edge.
What this does not tell you
Implied probability is the market's opinion, not the truth. Markets are usually well calibrated on big European leagues and considerably less so on lower divisions and obscure competitions — which is precisely why those markets carry wider margins and lower maximum stakes. Knowing the maths does not give you an edge. It gives you an accurate picture of the size of the disadvantage you are accepting, which is a different and much more useful thing.
Frequently asked questions
How do I calculate my winnings from decimal odds?
Multiply your stake by the decimal odds. That figure is the total returned to you, not the profit — it already includes your stake back. KES 100 at odds of 2.50 returns KES 250, of which KES 150 is profit. Deductions applied by the operator or by law come off after that, so the figure on your bet slip is the one that matters.
What probability do odds of 2.00 represent?
Divide 1 by the decimal odds. 1 ÷ 2.00 = 0.50, so odds of 2.00 imply a 50% chance. Odds of 1.50 imply 66.7%, odds of 4.00 imply 25%, odds of 10.00 imply 10%. This is called implied probability and it is the single most useful calculation in betting, because it converts a price into a claim you can actually disagree with.
Why do the implied probabilities of a match add up to more than 100%?
Because the excess is the bookmaker's margin, sometimes called the overround or the vig. On a football match with three outcomes, the three implied probabilities might total 105% or 108%. That surplus is the operator's built-in edge, and it is charged on every bet whether you win or lose. A lower total means a better price for you.
Are shorter odds safer?
Shorter odds mean the market thinks the outcome is more likely, not that it is safe. A 1.20 favourite still loses roughly one time in six if the price is accurate, and because the return is small, a handful of those losses wipes out a long run of wins. Nothing at any price is safe — see our page on why there is no such thing as a sure bet.
What are fractional and American odds?
Different notations for the same information. Fractional odds like 3/1 state profit relative to stake, so 3/1 equals decimal 4.00. American odds use +300 for the same price, or −150 for an odds-on favourite. Kenyan operators display decimal odds almost universally, so you can generally ignore the other two.
Do odds change after I place a bet?
Your bet is settled at the price shown on your bet slip at the moment it was accepted, not at the price on screen later. Odds move constantly as money comes in and as team news lands. Some operators offer an explicit acceptance setting for price changes — check what yours does before you assume a shortened price was applied to you.