Smarter Trades - Free Betfair Trading Tools

Free calculators for exchange bettors – no login, no cost.

Dutching, lay liability, hedging & staking – done properly.

Written by Alex Carter · Last reviewed:

Lay Liability Calculator (Featured Tool)

See exactly how much you stand to lose when laying a selection.

Lay side · Betfair / exchange

Laying a selection means you win if it loses, but your liability can be many times your stake. Use this calculator before you place a lay bet so you know exactly how much is at risk if the favourite or runner you oppose goes on to win.

How the calculation works

Core formula: Liability = (Lay Odds − 1) × Lay Stake

Worked example: Lay stake £10 at odds 4.5 with 2% commission.

  • Liability = (4.5 − 1) × £10 = £35.00.
  • Win profit (if selection loses) = £10 × (1 − 0.02) = £9.80.

For Betfair & exchange traders

Dutching, lay liability, hedging & staking – done properly.

Tools are informational only, not betting advice, and do not guarantee profit.

Use these free tools to size your stakes, balance your books and stress-test your edge before you place a trade. Everything runs in your browser – we never see your data.

What’s inside?

Nine quick calculators to help you trade smarter on Betfair, Matchbook, Smarkets and other exchanges.

About these tools

These free Betfair trading calculators are designed for exchange bettors who want to size stakes accurately and understand their edge before placing a trade. All calculations run locally in your browser – there is no login, no tracking of your inputs and no third-party API usage.

How to use these calculators

  1. Pick the tool that matches the decision you’re trying to make (dutching, lay, hedge, EV, staking or matched betting).
  2. Enter your odds, stakes and estimated win chances using decimal odds (e.g. 3.5 instead of 5/2).
  3. Review the profit, liability and expected value numbers shown in the result box.
  4. Use the output to adjust stakes or skip bets that don’t offer a clear edge.

The numbers are a guide, not a promise. Results in live markets will always vary and past performance is no guarantee of future returns.

Frequently asked questions

Do I need a Betfair account to use these tools?

No. These calculators work with decimal odds from any betting exchange or bookmaker. Just enter the odds and stakes you are using and the tools will calculate the figures for you.

Do you store my bets or track what I enter?

No. All calculations are performed in your browser only. We do not ask for an email address, do not require a login and do not store any of the values you type into the calculators.

Are these tools guaranteed to make me a profit?

Absolutely not. The calculators are designed to help you understand stakes, liability, expected value and bankroll management. They cannot predict results and do not guarantee that you will make money.

Can I use the tools for horse racing, football and other sports?

Yes. As long as your market uses decimal odds, you can use the dutching, lay, Fix-a-Bet, hedge, EV, Kelly, matched betting, acca and odds converter calculators on any sport, including horse racing, greyhounds, football, tennis and more.

Do I have to pay to use the calculators?

No. The tools on this page are free to use. In future there may be additional guides or resources linked from this site that are paid products, but the calculators themselves are free.

Guides & Resources

Learn the trading maths behind the tools

Use these deep-dive guides to sharpen your approach before you open a calculator.

Exchange trading glossary

New to exchange trading? Here are the key terms you will encounter across our calculators and guides.

Back bet
A bet that a selection will win. This is the traditional form of betting — you back something to happen and profit if it does.
Lay bet
A bet against a selection winning. On an exchange, laying means you take the role of the bookmaker and pay out if the selection wins.
Liability
The maximum amount you can lose on a lay bet. Calculated as (lay odds − 1) × lay stake. This amount is held by the exchange while the bet is open.
Green up
Placing an opposing bet to lock in a guaranteed profit regardless of the outcome. Also called "trading out" or "hedging."
Dutching
Spreading your total stake across multiple selections so that you receive the same profit whichever one wins. Useful when you rate several runners in a race.
Expected value (EV)
The average profit or loss per bet over the long run. Positive EV means the odds are in your favour; negative EV means they are not.
Implied probability
The probability of an outcome as suggested by the odds. Calculated as 1 ÷ decimal odds. Helps you compare the market's view with your own assessment.
Kelly criterion
A formula for calculating the optimal stake size based on your edge and the odds available. Maximises long-run bankroll growth while managing risk.
Commission
The fee charged by the exchange on net winnings in a market. Typically 2–5% on Betfair. Commission reduces your effective return on winning bets.
Overround
The margin built into a set of odds. If the implied probabilities of all outcomes sum to more than 100%, the excess is the overround — the bookmaker's or market's built-in edge.
Variance
The natural fluctuation in results over a series of bets. Even with a positive edge, short-term results can swing widely. Understanding variance helps you set realistic expectations.
Bankroll
The total amount of money you have set aside for trading. Proper bankroll management means never risking more than a small percentage on any single trade.
Matched betting
A technique that uses back and lay bets to extract value from bookmaker promotions. The maths ensures a guaranteed outcome regardless of the result.
Rule 4
A deduction applied to winning bets when a runner is withdrawn from a horse race after the market has formed. The deduction amount depends on the withdrawn runner's odds.
In-play trading
Placing bets while an event is live. Odds change rapidly during play, creating opportunities to back at higher odds and lay at lower odds (or vice versa).
Decimal odds
The odds format used by most exchanges. Represents the total return per unit staked, including the stake itself. Decimal 3.0 means a £1 bet returns £3 (£2 profit + £1 stake).

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