Fractional odds express profit relative to stake — not total return. The number on the left is what you win; the number on the right is what you must stake to win it.
At 5/2: stake £2 to profit £5. Total return: £7. If you stake £10 (five times the right-hand number), profit is £25, total return £35.
At 1/2 (also written as "1/2 on"): stake £2 to profit £1. Total return: £3. These odds below evens represent heavy favourites where the implied probability exceeds 50%. Odds-on prices are common in horse racing, where strong favourites regularly price at 4/7 or shorter.
Evens — written as "Evs" or 1/1 — means stake £1 to profit £1. Total return: £2. This is the fractional equivalent of decimal 2.00.
Converting fractional to decimal is the most useful calculation to have automatic:
Decimal = (Numerator ÷ Denominator) + 1
To convert decimal back to fractional: subtract 1 from the decimal, then express as a simplified fraction. 2.50 − 1 = 1.50 = 3/2 = 6/4 (the latter being the traditional UK expression).
A working knowledge of the most frequently used fractions saves time and prevents errors:
Fractions like 11/4, 13/8, 85/40, and 100/30 are deliberately non-standard. Traditional bookmakers used them to make direct price comparison between shops more difficult — if two bookmakers were both "offering 11/4" on the same horse, the customer might not notice that 11/4 at one and 3/1 at another is actually a different price. In an era before odds comparison websites, this slowed down the information available to bettors and protected bookmaker margins.
In modern online betting, these fractions persist in horse racing markets but are increasingly replaced by decimal displays. When you encounter an unusual fraction, convert to decimal immediately for a clear picture.
Horse racing in the UK and Ireland uses a specific pricing tradition: the Starting Price (SP). The SP is the officially recorded odds at the time the race starts, based on the last available on-course prices. If you take the SP on a bet rather than a fixed price, your payout is determined by whatever price the horse starts at — which can be dramatically different from the morning price.
A horse might be priced at 8/1 the morning before a race and start at 3/1 if significant money arrives on it during the day. Understanding SP vs fixed price is essential for anyone betting on racing, and the gap between the two is a direct signal of where informed money has moved.
Fractional odds express profit, not total return — always add 1 (in decimal terms) to compare like-for-like. Convert to decimal immediately when you need to think clearly; the fractional format's complexity is a historical artefact, not a feature.
