Market percentage calculator
Paste in every runner's price to see what the market adds up to, the bookmaker's margin, and each horse's fair odds once the margin is taken out.
Why the book matters
Add up every runner's implied chance and you'll almost always get more than 100%. That excess is how bookmakers make money whoever wins. For example, a five-runner market of 6/4, 2/1, 4/1, 6/1 and 10/1 adds up to 116.7%, a margin of 16.7%. The total tells you the margin across the whole race; it can't tell you whether any one price is good value.
How we use this at The Gallop
Every tip we've given since October 2025 is on our results page, settled with exactly these sums: each-way bets at standard place terms, Rule 4 where it applied, and the bigger of the advised price and the starting price, as bookmakers offering best odds guaranteed would pay. You can check any bet by putting it through the calculator.
Questions
What is the overround?
It's the total of every runner's implied chance. In a fair book it would be exactly 100%; bookmakers price above that, and the excess is their margin.
What is a fair price?
The odds a horse would be if the book added up to exactly 100%. The calculator scales each runner's chance down so the total is 100% and converts it back to odds.
What's a typical margin in horse racing?
It varies by race and bookmaker. Big fields and handicaps usually carry higher margins than small, competitive races. Comparing books shows you where the best value is.
More free betting tools
Each-way calculator
Win and place returns with place terms, Rule 4 and dead heats.
Bet calculator
Doubles to Goliaths, win or each way, with Rule 4 and dead heats.
Dutching calculator
Back several horses in one race for the same return whichever wins.
Lay bet calculator
Exchange liability, commission, and back-and-lay stakes.
Rule 4 calculator
The full Rule 4 deduction table and what a withdrawal costs your bet.
Each-way place terms
How many places are paid, and at what fraction, for any race.
Odds converter
Fractional, decimal, American and implied chance.
Staking calculator
Turn points into pounds for your betting bank.
Every tip, every race day
The Gallop Premium is £25 a month or £250 a year. Every tip goes to members' Telegram the moment it's posted, with a price and a stake, and every result goes on our public record, winners and losers. Cancel any time.