Betfair Odds Comparison: No-Vig Workflow to Find Real Price Edge

The most common mistake when comparing odds across bookmakers and the exchange is comparing raw prices without normalizing for margin.

That creates fake edges.

Step 1: Build a clean comparison set

For the same market and same timestamp, capture:

1. Best bookmaker odds.
2. Betfair back odds.
3. Betfair lay odds.
4. Exchange commission assumption.

If timestamps differ, comparison quality drops immediately.

Step 2: Convert odds to implied probability (without manual math)

Use the calculator directly instead of doing manual formulas:

Quick example (bookmaker side):

• Home 2.10 -> 47.62%
• Draw 3.40 -> 29.41%
• Away 3.60 -> 27.78%

Total: 104.81% (bookmaker margin present)

Step 3: Remove vig (no-vig normalization)

For practical execution, use the dedicated margin workflow instead of spreadsheet formulas:

This gives fairer probabilities and avoids overrating apparent price differences.

Step 4: Compare with exchange context

On exchange, do not use back price alone.

Check:

• Back price (entry)
• Lay price (exit potential)
• Spread width (execution friction)
• Available liquidity

A "better" back odd with poor lay depth is often unusable in real trading.

Step 5: Reject false edges

Reject setup if any of these fail:

• Edge is smaller than your minimum threshold.
• Market depth is too thin for your stake.
• Commission turns gross edge into weak net edge.

This one filter removes most low-quality entries.

Worked mini example

• Bookmaker Home 2.10 (no-vig adjusted fair probability ~45.4%)
• Betfair Back Home 2.24
• Betfair Lay Home 2.26
• Commission 2%

If your model fair odd is below 2.20, the exchange back may still be value after costs. If your model fair odd is 2.30+, this is likely noise, not edge.

Related tools and pages

• Odds Converter Calculator
• Overround Calculator
• Betfair Liquidity Guide
• Reading Betfair Odds Price Movements