Overround & Margin Calculator
Drop in every price from one market and see what the book really adds up to. Lower is better for you, and the fair odds show what each outcome would pay with the margin stripped out.
Market Margin Checker
Add each outcome's price to total the book and pull out the fair odds
Why markets add up to more than 100%
Home, draw or away: one of them always lands, so the true chances total exactly 100%. Bookmakers price them so the implied chances total more. That extra slice is their margin, and you pay it on every bet.
Book % = 100 ÷ price 1 + 100 ÷ price 2 + 100 ÷ price 3 …
Take 100 away from the book % and what's left is the margin.
Pricing up a Saturday 3pm
Home 1.72, draw 3.90, away 5.25. That's 58.14% + 25.64% + 19.05% = 102.83%. A margin under 3% is keen pricing. Divide each implied chance by 1.0283 and the fair prices come out at 1.77, 4.01 and 5.40.
Same game, another bookmaker: 1.66 / 3.75 / 5.00 totals 106.91%. You'd be paying well over double the margin for exactly the same match.
What the number tells you
- •Low book, sharp prices. The closer a market gets to 100%, the more its prices tell you about the real chances. Strip the margin and use those fair odds as your benchmark.
- •Two-way markets count too. Over/under 2.5 goals at 1.85 / 1.95 totals 105.34%, a 5.34% margin on a market with only two outcomes.
- •Check it live. Margins don't stay fixed once the ball is rolling. Run the in-play prices through and you'll see exactly what you're paying at that moment.
- •Under 100% is a gift. If the best prices from different bookmakers total less than 100%, you've found an arb. The arbitrage calculator does the staking.
Explore More Betting Tools
Odds Calculator
Flip any price between decimal, fractional and American.
Dutching Calculator
Back several selections and get the same return whichever wins.
Cash Out Calculator
Work out the hedge that locks in a profit or caps a loss.
Free Bet Calculator
Know what a free bet is really worth before you use it.
Arbitrage Calculator
Split your stake across bookmakers to lock in a sure return.
EV Calculator
Test whether a price beats your own probability.
Kelly Criterion
Size each bet to your edge and protect the bankroll.
Each Way Calculator
Get the win and place return on an each-way bet.
Acca Calculator
Stack up to 15 legs and see the payout in seconds.