How do decimal betting odds work?

Decimal odds show your total return per unit staked, including the stake. Multiply your stake by the decimal odds to get the total payout: a $10 bet at 2.50 returns $25 ($15 profit plus your $10 stake). It's the easiest format for comparing prices.

What does +150 or -200 mean in American odds?

A plus figure is the profit on a $100 stake: +150 means you win $150 profit for every $100 staked. A minus figure is how much you must stake to win $100 profit: -200 means you stake $200 to win $100. Plus is an underdog, minus is a favourite.

How do I turn odds into a probability?

Implied probability equals 1 divided by the decimal odds. Odds of 2.50 imply a 40% chance (1 ÷ 2.50). Across a whole market these implied probabilities add up to more than 100% — the extra is the bookmaker's margin.

How betting odds work — decimal, fractional & American explained

Last updated: 2026-07-13 · Gamblerfy editorial team

Every set of betting odds says two things at once: how likely an outcome is, and how much you'd win. Three formats show the same information in different ways — once you can read one and convert to the others, no price can confuse you.

Decimal odds — the simplest

Decimal odds show your total return per $1 staked, stake included. Multiply your stake by the odds: a $10 bet at 2.50 returns $25 — $15 profit plus your $10 back. Anything above 2.00 is "odds against" (profit bigger than stake); below 2.00 is "odds on" (profit smaller than stake); 2.00 is evens.

Fractional odds — the traditional UK format

Fractional odds (like 3/2, said "three to two") show profit relative to stake: 3/2 means $3 profit for every $2 staked. Your stake comes back on top. To convert to decimal, divide and add one: 3 ÷ 2 = 1.5, + 1 = 2.50 — the same price as the decimal example.

American (moneyline) odds

Positive (+150): profit on a $100 stake. +150 wins $150 profit per $100 — an underdog.
Negative (−200): stake needed to win $100. −200 means risk $200 to win $100 — a favourite.

All three side by side

Decimal	Fractional	American	Implied probability
1.50	1/2	−200	66.7%
1.91	10/11	−110	52.4%
2.00	1/1 (evens)	+100	50.0%
2.50	3/2	+150	40.0%
3.00	2/1	+200	33.3%

Skip the mental math — the Odds Converter turns any price into all three formats plus implied probability and payout instantly.

Odds are a probability in disguise

The most useful trick: implied probability = 1 ÷ decimal odds. Odds of 2.50 imply a 40% chance (1 ÷ 2.50). This is what lets you judge whether a price is fair. Add up the implied probabilities of every outcome in a market and you'll get more than 100% — that overround is the bookmaker's margin, the built-in edge you're paying. Stripping it out gives the fair price, and comparing your own estimate to it is the whole idea behind value betting.

Understanding odds makes you a sharper reader of prices — it doesn't remove the house edge built into them. Bet within a fixed budget for entertainment. Read our responsible gambling guide.

Come across a term you don't know? Our betting & bonus glossary defines them all in plain English.