How to Calculate Betfair Break-Even Odds (With and Without Commission)

Understanding your break-even odds is one of the simplest ways to avoid negative-EV betting on Betfair. This guide walks you through the exact formula, explains how commission changes the numbers, and shows how to check profitability properly using the EV calculator on Smarter Trades.

What Are Break-Even Odds?

Break-even odds tell you the minimum price you need for a bet to be “mathematically fair.” At this price, your expected long-term profit is exactly zero.

If you take odds shorter than your break-even number, the bet is negative EV. If you take higher odds, the bet is positive EV.

The Simple Break-Even Formula (No Commission)

If you know your estimated win probability, break-even odds are calculated as:

breakEvenOdds = 1 / winProbability

Examples:

50% win probability → break-even odds = 2.00
40% win probability → break-even odds = 2.50
25% win probability → break-even odds = 4.00

If the market offers higher odds than your break-even point, the bet is theoretically profitable.

How Betfair Commission Changes Break-Even Odds

Betfair charges commission on winnings, which raises your real break-even odds because your net win is smaller.

A simple adjusted formula is:

breakEvenOdds = 1 / (winProbability × (1 − commissionRate))

Example with 5% commission:

Win probability: 50%
Adjusted break-even odds = 1 ÷ (0.50 × 0.95) = 1 ÷ 0.475 = 2.105

This means that at 2.00, the bet is actually negative EV once commission is included. You would need odds of at least 2.10 to break even.

Using the Smarter Trades EV Calculator

The fastest way to confirm real profitability (including commission) is to use the free EV calculator: Open EV Calculator.

Simply enter:

The odds you are being offered
Your estimated win probability
Your stake
Your commission rate

You’ll instantly see:

Your expected value per bet
Your break-even win probability
Your break-even odds
Net profit after commission

Example: Market Odds vs Break-Even Odds

Let’s say you estimate a horse wins 35% of the time (0.35 probability). Without commission:

Break-even odds = 1 ÷ 0.35 = 2.86

With 5% commission:

Adjusted break-even odds = 1 ÷ (0.35 × 0.95) ≈ 3.01

If the market offers 3.20, that is above both break-even values → a positive-EV opportunity.

Break-Even for Lay Betting

When laying, the concept flips. Instead of calculating odds you need, you calculate the minimum win probability the runner must have for the lay to be profitable.

You can plug lay odds into the Smarter Trades EV calculator, which handles the maths for both sides.

Why Break-Even Odds Are So Useful

Calculating break-even odds helps you:

Avoid negative-EV bets
Spot overpriced runners quickly
Compare your tissue prices to the market
Determine whether odds are truly “value” or just tempting
Build consistent, data-driven betting habits

Frequently Asked Questions

Are break-even odds enough to decide a bet?

No. Break-even odds show whether the price is fair, but EV shows how profitable the bet is. Use break-even odds as a filter, not the final decision.

Do I include commission every time?

Yes — always include commission for Betfair. Without commission, your calculations are not realistic.

Can break-even odds help with lay betting?

Absolutely. Lay betting also relies on win probabilities and implied probabilities, which you can convert into break-even thresholds.

Where can I calculate EV and break-even odds automatically?

Use the Smarter Trades EV calculator here: Smarter Trades EV Tool.