Betting Odds Formats: Decimal, Fractional and American Explained
A bettor in Poland sees only decimal odds — the sole format used by every licensed, Ministry-of-Finance-permitted bookmaker in the country. But watch one foreign sports broadcast, visit a UK betting site, or read an American pre-match analysis, and you’ll run into completely different notations for the exact same information: “3/2” or “+150”. This guide explains all three formats — decimal, fractional (UK) and American (moneyline, US) — how to read them, how to convert between them, and why, despite the different notation, they all carry exactly the same information about the price and the bookmaker’s margin. Updated: September 2026.
Decimal odds — the standard in Poland and most of Europe
Decimal odds are the simplest of the three formats: they show directly how much you receive for every unit staked, including your returned stake. Odds of 2.50 mean that staking 100 zl returns 250 zl if you win — 150 zl profit plus your 100 zl stake back. Odds of 1.50 mean a 150 zl payout on the same stake, i.e. 50 zl profit. The formula is always the same: payout = stake x odds. That simplicity — one number, one multiplication — is exactly why decimal odds dominate the European market, including the whole of Poland’s regulated betting market.
Fractional odds — how to read them
The British format, still standard in the UK and in British horse-racing and football coverage. The notation a/b (e.g. 3/2, 4/5, 1/1) shows only your profit relative to the stake — the returned stake isn’t part of the number itself. Odds of 3/2 mean: for every 2 zl staked, you profit 3 zl (plus your stake back separately). Odds of 1/2 mean: for every 2 zl staked, you profit just 1 zl — typical for a clear favourite. Odds of 1/1 (“evens”) mean profit equal to the stake — exactly the same as decimal odds of 2.00.
American odds (moneyline) — how to read them
Used in the US, mainly for the NBA, NFL and MLB. It comes in two forms, distinguished by sign. Positive odds (e.g. +150) show how much you’d win on a 100-unit stake — this applies to “long” odds, i.e. decimal 2.00 and above (underdogs). Negative odds (e.g. −200) show how much you need to stake to win 100 units — this applies to favourites, i.e. decimal odds below 2.00. The boundary between positive and negative notation always falls exactly at decimal odds of 2.00, which the American format writes as +100.
Converting decimal to fractional — formula and examples
Formula: fraction = (decimal odds − 1), written as the simplest possible fraction. Step by step for 2.50: 2.50 − 1 = 1.50, and 1.50 as a fraction is 3/2 (since 3 ÷ 2 = 1.50). For 2.75: 2.75 − 1 = 1.75, which as a fraction is 7/4 (7 ÷ 4 = 1.75). For 1.50: 1.50 − 1 = 0.50, i.e. 1/2. For 1.80: 1.80 − 1 = 0.80, i.e. 4/5 (4 ÷ 5 = 0.80). The reverse direction works identically: to get back to decimal from a fraction, divide the numerator by the denominator and add 1 — for 3/2, 3 ÷ 2 = 1.50, plus 1 = 2.50, exactly the odds we started with.
Converting decimal to American — formula and examples
For decimal odds of 2.00 and above (positive American notation): American = (decimal odds − 1) x 100. For odds of 2.50: (2.50 − 1) x 100 = 1.50 x 100 = +150. For odds of 2.75: (2.75 − 1) x 100 = 1.75 x 100 = +175. For odds of 3.00: (3.00 − 1) x 100 = 2.00 x 100 = +200.
For decimal odds below 2.00 (negative American notation): American = −100 ÷ (decimal odds − 1). For odds of 1.50: −100 ÷ (1.50 − 1) = −100 ÷ 0.50 = −200. For odds of 1.80: −100 ÷ (1.80 − 1) = −100 ÷ 0.80 = −125. Checking −200 the other way: 100 ÷ 200 = 0.50, plus 1 = 1.50 — the same decimal odds we started with, so the formulas agree.
Conversion table — the most common odds in three formats
| Decimal odds (PL) | Fractional odds (UK) | American odds (US) |
|---|---|---|
| 1.50 | 1/2 | −200 |
| 1.80 | 4/5 | −125 |
| 2.00 | 1/1 (evens) | +100 |
| 2.50 | 3/2 | +150 |
| 2.75 | 7/4 | +175 |
| 3.00 | 2/1 | +200 |
| 4.00 | 3/1 | +300 |
Every column in this table describes the same price — only the notation differs. Decimal odds of 2.00 are simultaneously 1/1 in fractional and +100 in American: three different symbols, one and the same payout.
Odds format and implied probability
Whatever the format, any price converts to an approximate probability of winning — just reduce it to decimal form first, then divide 1 by that number. Odds of 2.50 (i.e. 3/2, i.e. +150) correspond to an implied probability of 1 ÷ 2.50 = 40%. Odds of 1.50 (i.e. 1/2, i.e. −200) give 1 ÷ 1.50 ≈ 66.7%. The full formula, more examples and an explanation of why the total for a whole market always exceeds 100% are in our guide to implied probability.
Why this matters at all for a bettor in Poland
With any of the 17 licensed Polish bookmakers, you never need to know the fractional or American format to place a bet — the slip always shows decimal odds. This knowledge is useful in three specific situations: when you’re following a foreign broadcast and a price appears in a different format, when you’re reading a pre-match analysis published by foreign media, or when you’re comparing your own pick with what you see on the social profiles of foreign tipsters — without conversion skills it’s easy to misjudge whether a given price is actually attractive.
Common mistakes reading foreign odds
- Confusing fractional odds with probability — 1/2 is NOT 50%; it’s profit equal to half your stake, which corresponds to decimal odds of 1.50 and an implied probability of about 66.7%.
- Treating the American number as decimal odds — a price of +150 is NOT 150.0 in decimal format; it’s equivalent to decimal odds of 2.50.
- Ignoring the sign on American odds — mixing up +150 with −150 flips the meaning from a clear underdog to a clear favourite.
- Rounding fractions “by eye” — 8/13 is not the same as 2/3; for unusual fractions, always do the full division rather than estimating.
Odds format and choosing a bookmaker
Since format is purely notation, not the actual value of the odds, choosing a licensed bookmaker should rest on something else entirely — above all on how much margin is baked into the decimal price itself. Among Ministry-of-Finance-licensed operators, AdmiralBet and Betclic stand out for a lower margin (i.e. statistically better prices). See the full margin mechanism in bookmaker overround, and the complete line-up of all 17 licensed operators in our ranking of licensed bookmakers.
Does either format give the bookmaker a higher margin?
No — that’s one of the more common myths. Margin is a property of the whole market (the relationship between every possible outcome’s odds), not of how a single price is written. Decimal odds of 1.90, fractional 9/10 and American −111 are three notations for exactly the same number and exactly the same margin — switching format doesn’t change a single grosz of your potential payout.
Fractional odds outside the UK — where else it turns up
The fractional format didn’t disappear as decimal odds expanded across Europe — it’s still the standard at British horse-racing tracks and in related broadcasts, and it turns up occasionally in boxing and combat-sports analysis published by British media. If you’re watching a foreign broadcast of the Grand National or a similar event, odds of “5/1” or “11/4” aren’t a random notation — they’re exactly the same mechanism this guide explains, so just apply the conversion formula from earlier.
American odds exactly at the boundary — why 2.00 is a special case
Decimal odds of 2.00 are the one point where both American conversion formulas give the same result. The formula for 2.00 and above: (2.00 − 1) x 100 = +100. The formula for below 2.00, applied hypothetically at exactly this point: −100 ÷ (2.00 − 1) = −100. American convention adopts the positive notation here (+100), not the negative one — that’s a purely formal convention, not a second, contradictory value. Every decimal price above 2.00 (e.g. 2.01) is always written with a positive sign, and every price below 2.00 (e.g. 1.99) with a negative one.
Exercise — recognise the same price in three notations
A short, fully worked example to check whether the formulas above actually agree. Starting point: fractional odds of 2/3. Step 1 — convert to decimal: 2 ÷ 3 = 0.6667, plus 1 = 1.6667, shown by a bookmaker in practice as 1.67. Step 2 — convert to American: since the odds are below 2.00, we use −100 ÷ (odds − 1) = −100 ÷ 0.6667 ≈ −150. Step 3 — check the other way: for −150, 100 ÷ 150 = 0.6667, plus 1 = 1.6667 — exactly the decimal odds we started with. Three different notations (2/3, 1.67, −150), one and the same number.
The other direction — from American back to decimal and fractional
To practise conversion starting from the American format, take odds of −175, a typical notation for a clear favourite in an American broadcast. Step 1 — convert to decimal: the odds are negative, so decimal = 1 + 100 ÷ 175 = 1 + 0.571429 = 1.571429, shown as 1.57. Step 2 — convert to fractional: 1.571429 − 1 = 0.571429, which as a fraction is exactly 4/7 (4 ÷ 7 = 0.571429). Step 3 — full check: from 4/7 back to decimal — 4 ÷ 7 = 0.571429, plus 1 = 1.571429; from 1.571429 back to American — since the odds are below 2.00, −100 ÷ 0.571429 = −175, exactly the American odds we started with. All three formats agree again.
What this means for you in practice
If you never watch foreign broadcasts or read foreign-language analysis, this knowledge is purely trivia — with a licensed Polish bookmaker you’ll always see decimal odds and never need to convert anything. It’s useful in three specific situations: (1) you’re following a match on a foreign broadcast and the commentator or on-screen graphic quotes fractional or American odds; (2) you’re reading a pre-match analysis from a foreign site and want to judge whether the “value” it claims actually matches what you see with your own licensed bookmaker; (3) you’re comparing prices from different markets (e.g. US and Europe) on the same international event, such as a major tennis tournament or a competition involving Polish athletes abroad. In each case, first convert the foreign price to decimal using the formulas in this guide, then compare it with the licensed operators in our ranking of licensed bookmakers — comparing odds across two different formats “by eye” is a quick route to misjudging which price is actually better.
Odds format and implied margin — why eyeballing it fails
Imagine comparing two sources: a licensed Polish bookmaker shows odds of 1.91, while a foreign site quotes the fraction 10/11 for the same outcome. At first glance it’s hard to tell which is better — until you convert both to a common format. 10/11 as decimal: 10 ÷ 11 = 0.9091, plus 1 = 1.9091, i.e. 1.91 rounded — exactly the same price, just written differently, not two different offers. Comparing them without conversion, “10/11” might look less attractive than “1.91”, even though they’re identical values. Only converting to a common decimal format allows a fair comparison — exactly as when comparing prices between two licensed bookmakers, covered in implied probability.
Frequently Asked Questions
Which odds format do Polish bookmakers use?
Decimal odds — the standard used by all 15 MF-licensed bookmakers operating legally in Poland. You will mostly meet fractional and American odds in foreign broadcasts, on screenshots from UK or US betting sites, or in international pre-match analysis — not on a licensed Polish operator’s site.
How do I convert fractional odds to decimal in my head?
Divide the numerator by the denominator and add 1. For 3/2: 3 ÷ 2 = 1.50, plus 1 = 2.50. For 4/5: 4 ÷ 5 = 0.80, plus 1 = 1.80. The full conversion table with ready-made examples is above in this article.
Why is American odds sometimes positive and sometimes negative?
Positive (e.g. +150) shows how much you would win on a 100 stake — it applies to decimal odds of 2.00 and higher. Negative (e.g. −200) shows how much you need to stake to win 100 — it applies to decimal odds below 2.00, i.e. favourites. The boundary between the two is always decimal odds of 2.00.
Does switching the odds format change the bookmaker’s margin?
No. The format is purely a way of writing the same number — the margin comes from the relationship between the odds of every outcome on a given market, not from how you choose to display one of them. We explain the margin mechanism and walk through a full numerical example in bookmaker overround.
Is it worth using a calculator to convert odds?
For checking a single price occasionally, the formulas in this guide are enough — but for an accumulator with several legs it is faster and safer to use a ready-made tool. See our betting calculators.