Margin Calculator
Enter the book's odds on every outcome of a market and see the margin — the overround the book builds in. A fair market sums to 100%; everything above that is the house edge.
HIDDEN MARKET TAX
This market is priced above fair value. The bookmaker has the edge.
4.71%
BOOKMAKER EDGE
Market type
Use decimal odds (e.g. 1.91). For 2-way markets only.
Fair market sum
100.00%
Perfectly balanced
This market sum
104.71%
Over fair value
Bookmaker edge
4.71%
Your hidden cost
| Outcome | Fair probability (no margin) | This market (book) | Overround added |
|---|---|---|---|
| 1 | 50.00% | 52.36% | +2.36% |
| 2 | 50.00% | 52.36% | +2.36% |
| TOTAL | 100.00% | 104.71% | +4.71% |
At 4.71% margin, the book keeps €4.71 for every €100 you bet — no matter which outcome wins. This is the hidden tax built into the prices.
-€4.71
Expected cost per €100 bet
0% – 2%
Sharp market
Very efficient
2% – 5%
Good market
Acceptable
5% – 7%
Expensive
Be selective
7%+
Dangerous
High hidden tax
Your market: 4.71%
(Good market)
Margin = hidden tax
The bookmaker adds margin to every outcome so the probabilities sum to more than 100%.
Sharp books = lower margin
The best books compete on price and take less from bettors.
Parlays multiply margin
Each extra leg compounds the margin, making long parlays very expensive.
Remove the margin or find better prices.
You bet
€100
Market margin
4.71%
Book keeps
€4.71
Winners get
€95.29
No matter who wins, the book's edge is locked in.
Like what you see? Log this bet in the Bet Tracker and watch your edge play out over time.
Keep going. These tools work well together.
100% Private
All calculations run on your device.
Instant Results
Advanced formulas. Zero waiting.
Trusted by Winners
Used by thousands of sharp bettors daily.
Learn & Improve
Turn numbers into knowledge and profit.
All calculations are private and performed on your device.