Guides · last updated 2026-08-30

How to read betting odds: decimal, fractional and American

The three odds formats explained, how to convert between them in one step each, and why decimal is the only sensible format for comparing prices between bookmakers.

Written and maintained by Marek Ohanka, publisher, WhichBookmaker

Three formats describe the same thing in three different ways. Which one you see depends mostly on where the operator is from: fractional in British and Irish betting shops, decimal across Europe and most of the modern online market, American in the United States.

None is more accurate than another. But one of them makes comparison easy and two of them make it hard, which is worth knowing before you decide a price looks generous.

Decimal odds

Decimal odds tell you the total return on a one-unit stake, including the stake itself.

A price of 3.50 returns £3.50 for every £1 staked: £2.50 profit plus your £1 back.

  • Return = stake × odds
  • Profit = stake × (odds − 1)

Anything above 2.00 means the outcome is considered less likely than a coin flip. Anything below 2.00 means more likely. Exactly 2.00 is an even-money proposition.

Fractional odds

Fractional odds tell you the profit relative to the stake, ignoring the stake’s return.

A price of 5/2 (“five to two”) pays £5 profit for every £2 staked, plus your £2 back — £7 in total.

  • Profit = stake × (numerator ÷ denominator)
  • Return = profit + stake

The awkwardness is that the denominators vary. Comparing 5/2 against 12/5 requires arithmetic; comparing 3.50 against 3.40 does not. This is why British bookmakers have been quietly offering a decimal toggle for years, and why you should use it.

To convert: decimal = (numerator ÷ denominator) + 1. So 5/2 becomes (5 ÷ 2) + 1 = 3.50.

American odds

American odds — sometimes called moneyline — use a positive or negative number anchored to 100 units.

  • A positive figure is the profit on a 100-unit stake. +250 means stake 100, win 250 profit.
  • A negative figure is the stake needed to win 100 units of profit. −150 means stake 150 to win 100.

The sign carries the information: negative means favourite, positive means underdog, and the crossover point is even money.

To convert:

  • Positive: decimal = (American ÷ 100) + 1. So +250 → 3.50.
  • Negative: decimal = (100 ÷ |American|) + 1. So −150 → 1.667.

Implied probability

Every price is a probability wearing a costume. From decimal odds:

implied probability = 1 ÷ decimal odds

A price of 4.00 implies 25%. A price of 1.25 implies 80%.

This is the single most useful conversion in betting, because it lets you ask a concrete question: do I think this outcome is more likely than the price says? That is a harder question than “does 4.00 feel big?”, and a far more honest one.

It is also how you find the bookmaker’s fee. Add up the implied probabilities of every outcome in a market and the total will exceed 100%; the excess is the margin, and it is explained fully in our guide to bookmaker margins.

Conversion table

Decimal Fractional American Implied probability
1.20 1/5 −500 83.33%
1.50 1/2 −200 66.67%
1.91 10/11 −110 52.36%
2.00 1/1 (evens) +100 50.00%
2.50 3/2 +150 40.00%
3.00 2/1 +200 33.33%
4.33 10/3 +333 23.09%
5.00 4/1 +400 20.00%
11.00 10/1 +1000 9.09%
26.00 25/1 +2500 3.85%

Two rows are worth memorising. 2.00 = evens = +100 = 50% is the pivot the whole system turns on. And 1.91 = 10/11 = −110 is the standard price on a two-way market at a mainstream book — if you recognise it on sight, you will recognise when you are being offered worse.

Why decimal wins for comparison

Say two bookmakers price the same selection:

  • Book A: 11/8
  • Book B: 1.36

Which is better? In fractional you have to work it out. In decimal it is instant: 11/8 = (11 ÷ 8) + 1 = 2.375, against 1.36. Book A is dramatically better — but only once both prices are in the same units.

That example is deliberately extreme. The realistic case is worse, because the differences are small enough to shrug at:

Book A Book B
Fractional 5/6 4/5
Decimal 1.833 1.800
Implied probability 54.5% 55.6%

Three per cent better at Book A on that bet. Shrug at that difference on every bet for a season and it becomes the difference discussed in the margin guide.

Set every account you hold to decimal. It costs nothing and it makes the comparison automatic.

Fractional rounding, and why prices look odd

Fractional odds come from a fixed traditional ladder — 4/5, 5/6, 10/11, evens, 11/10, 6/5, 5/4 and so on. There is no neat fraction between many of those steps, so a book pricing in fractions has to round to the nearest rung.

Rounding is not neutral. It goes in the operator’s favour more often than yours, which is a second, quieter reason decimal pricing tends to be slightly better value — the price can sit exactly where the model puts it rather than at the nearest traditional fraction below.

Each-way betting, briefly

An each-way bet is two bets: one on the selection to win, one on it to place. A £10 each-way bet costs £20.

The place part pays at a fraction of the win odds — commonly 1/4 or 1/5, stated in the market terms — across a stated number of places. A 10.00 shot at 1/5 odds a place returns 2.80 on the place portion: (9 × 0.2) + 1.

The place terms vary by event and by operator, and they matter as much as the headline price on any big-field race. Check them before assuming two operators are offering the same bet.