Horse Racing Odds Converter
Convert between UK fractional, decimal, and American odds for horse racing
Formula:Decimal = (Num / Denom) + 1
Enter Odds
Input odds in any format
Converted Odds
Against odds
Fractional (UK/Irish)
5/1
Decimal
6.00
American
+500
Implied Probability
16.67%
Example Payout on $10 Stake:
Profit: $50.00
Total Return: $60.00
Common Odds Examples
Quick-start with common scenarios
Key Facts: UK/Irish Odds
Important information for horse racing bettors
- UK/Irish racing primarily uses fractional odds (5/1, 11/4)
- "Evens" (1/1) means you win equal to your stake
- Odds-on favorites have fractional odds below 1/1
- Decimal odds include your stake in the return
- American odds use +/- format based on $100
- All formats represent the same implied probability
- SP (Starting Price) is determined at race start
- Board prices update as betting progresses
Frequently Asked Questions
Common questions about horse racing odds
How do UK fractional odds work?
Fractional odds like 5/1 show profit relative to stake. At 5/1, you win $5 profit for every $1 staked. "Evens" or 1/1 means equal profit to stake. Odds like 4/6 (less than 1/1) indicate a favorite where you risk more than you win.
How do I convert fractional to decimal?
Divide the first number by the second and add 1. For 5/1: (5 / 1) + 1 = 6.00 decimal. For 4/6: (4 / 6) + 1 = 1.67 decimal. The +1 accounts for getting your stake back.
What are American odds?
American odds use +/- format. Positive odds (+200) show profit on $100 stake. Negative odds (-150) show stake needed to win $100. +200 means bet $100 to win $200 profit. -150 means bet $150 to win $100 profit.
Why do UK bookmakers use fractional odds?
Fractional odds are traditional in UK and Irish horse racing, dating back centuries. They clearly show the profit-to-stake ratio and are easy to calculate mentally. Many regular punters find them more intuitive than decimal format.
What does "odds-on" mean?
Odds-on refers to odds where the first number is smaller than the second (like 4/6, 1/2, or 1/3). These represent favorites where you risk more than your potential profit. At 1/2, you bet $2 to win $1 profit.
How this works
Calculations follow the published mathematics of the game — combinatorics for cards, probability theory for dice, and expected-value accounting for wagers. Results are verified against independent references (primarily Wizard of Odds). No calculation here is an opinion or recommendation; it is arithmetic applied to the rules of the game.
What this tool can’t do
When to consult a professional
This tool computes probability and expected value. It is not a betting system and cannot predict the outcome of any individual wager. If gambling is causing problems for you or someone you know, call the National Problem Gambling Helpline at 1-800-GAMBLER.
Sources
- [1]Wizard of Odds — Michael Shackleford, ASAIndustrywizardofodds.comAccessed Apr 21, 2026
Actuary; widely cited casino-game probability reference. Used for house-edge and EV verification.
- [2]National Council on Problem GamblingOfficial sourcencpgambling.orgAccessed Apr 21, 2026
Responsible-gambling guidance and 1-800-GAMBLER helpline.
Joseph OrdunaFounder & Software Engineer
Full-stack software engineer specializing in embedded systems, web architecture, and AI/ML. Founder of Practical Web Tools. Built the gesture-controlled drone IP acquired by KD Interactive (Aura Drone, sold on Amazon).