Methodology
How Footylab Reads Overround and Margin
This page explains the plain-English logic behind H2H overround, bookmaker margin, ATS margin proxy, and why lower margin usually means cleaner prices.
Step 1
Convert each odd into implied probability
Step 2
Add the listed probabilities together
Step 3
Measure how far above 100% the market sits
1. What overround means
Overround is the bookmaker's built-in margin for a market.
If the implied probabilities of all listed outcomes add up to exactly 100%, the market is perfectly fair before margin.
If those implied probabilities add up to more than 100%, the difference above 100% is the overround.
2. The H2H formula
For H2H, Footylab calculates implied probability as 1 divided by the decimal price for each team.
Those implied probabilities are summed across the two listed outcomes inside the same bookmaker market.
True overround is total implied probability minus 1. Overround percent is that result multiplied by 100.
3. H2H example
Team A at 1.50 implies 66.7%. Team B at 2.50 implies 40.0%.
The total implied probability is 106.7%, so the overround is 6.7%.
That means the bookmaker has baked roughly 6.7% of margin into the market.
4. How to interpret it
Lower H2H overround or a lower ATS margin proxy usually means cleaner, more competitive prices for punters.
Higher values mean more bookmaker margin or more expensive ATS pricing, so any value signal deserves more caution.
Margin context supports the pricing read. It does not replace Footylab fair price, value score, market edge, or the headline verdict.
5. Why H2H is cleaner
H2H overround is usually reliable because the bookmaker market normally has two outcomes from the same board.
That makes the bookmaker margin easier to interpret as a clean market-quality signal.
Footylab keeps the calculation bookmaker-specific, so it does not mix odds from different books into a synthetic margin number.
6. ATS caveat
ATS does not have mutually exclusive outcomes, so summing every listed player price from one bookmaker does not produce a meaningful true overround.
Footylab therefore uses an ATS margin proxy instead. For each comparable listed player, it builds a median implied-probability baseline across bookmakers.
Each bookmaker is then compared against that baseline only across the subset of players where a fair cross-bookmaker comparison exists.
Negative ATS proxy values mean the book looks generous versus the comparable market baseline. Positive values mean the board looks more expensive.