Back and Lay Calculator: Master Betting Exchange Trading

Betting exchanges let you both back (bet for) and lay (bet against) outcomes. Our calculator shows exact liability, profit potential, and helps you trade positions for guaranteed profit through back-to-lay or lay-to-back strategies.

What Is Back and Lay Betting?

On exchanges like Betfair, you can back selections (traditional betting) or lay selections (act as the bookmaker, accepting others' bets against that outcome).

Quick Answer: Backing means betting FOR something to win; laying means betting AGAINST it (you pay out if it wins). Lay liability = Stake × (Odds - 1). A £10 lay at 3.0 means £20 liability—you pay £20 if it wins, keep £10 if it loses. Exchanges charge 2-5% commission on winning bets.

How to Use Our Back-Lay Calculator

Use the Back-Lay Calculator →

Enter back/lay odds to calculate liability, profit, and exchange commission.

Step-by-Step Instructions

1. Select Bet Type: Back or Lay

2. Enter Odds: Decimal format

3. Input Stake/Liability: Depending on bet type

4. Enter Commission: Typically 2-5%

5. View Results: Profit, liability, net return

Input Fields Explained

Field	Description	Example
Bet Type	Back or Lay	Lay
Odds	Decimal odds	3.50
Stake	Amount (back)	£100
Liability	Risk (lay)	£250
Commission	Exchange %	5%
Gross Profit	Pre-commission	£100
Net Profit	After commission	£95

Back vs Lay Explained

Backing (Traditional Bet)

Outcome	Result
Selection wins	Win (Stake × Odds - Stake)
Selection loses	Lose stake

Example: £10 back at 4.0

• If wins: £30 profit (£40 return - £10 stake)
• If loses: -£10

Laying (Acting as Bookmaker)

Outcome	Result
Selection wins	Lose liability
Selection loses	Win stake

Example: £10 lay at 4.0

• If wins: -£30 (you pay out)
• If loses: +£10 (you keep their stake)

Calculating Lay Liability

Liability Formula

Liability = Lay Stake × (Lay Odds - 1)

Liability Examples

Lay Stake	Odds	Liability	If Loses	If Wins
£10	2.0	£10	+£10	-£10
£10	3.0	£20	+£10	-£20
£10	5.0	£40	+£10	-£40
£10	10.0	£90	+£10	-£90

Liability Management

Odds	Liability Ratio	Risk Level
1.5-2.0	0.5-1.0× stake	Low
2.0-3.0	1-2× stake	Medium
3.0-5.0	2-4× stake	High
5.0+	4× stake+	Very High

Exchange Commission

How Commission Works

Exchanges charge commission on net winnings per market:

Net Profit = Gross Profit × (1 - Commission Rate)

Commission Comparison

Exchange	Standard Rate	Reduced Rate
Betfair	5%	2% (high volume)
Smarkets	2%	1% (loyalty)
Betdaq	2%	0% (promos)
Matchbook	1.5%	-

Commission Example

Gross Win: £100 Commission: 5% Net Profit: £100 × 0.95 = £95

Back-to-Lay Trading

What Is Back-to-Lay?

Back at higher odds, then lay at lower odds when price shortens to lock in profit.

Example Trade

Step 1: Back Horse at 6.0 with £50 Step 2: Price shortens to 4.0 Step 3: Lay Horse at 4.0

Calculations:

• Back profit (if wins): £250
• Lay stake needed for equal profit: £62.50
• Lay liability: £187.50

Outcomes:

• If wins: £250 (back) - £187.50 (lay liability) = £62.50
• If loses: -£50 (back) + £62.50 (lay win) = £12.50

Finding the Right Lay Stake

Lay Stake = (Back Stake × Back Odds) / Lay Odds
Equal Profit: Lay Stake = (Back Stake × (Back Odds - 1)) / (Lay Odds - 1)

Lay-to-Back Trading

What Is Lay-to-Back?

Lay at lower odds, then back at higher odds when price drifts to lock in profit.

Example Trade

Step 1: Lay Horse at 3.0 with £50 (liability £100) Step 2: Price drifts to 5.0 Step 3: Back Horse at 5.0

Calculations:

• If horse loses: +£50 (lay) - back stake
• If horse wins: -£100 (lay) + back winnings

For equal profit:

• Back stake = £25 at 5.0
• If wins: -£100 + £100 (5×25-25) = £0... wait, need to recalculate

Better formula:

• For profit whatever happens, hedge with back £33.33 at 5.0
• If wins: -£100 + £133.32 = £33.32
• If loses: +£50 - £33.33 = £16.67

Real-World Examples

Example 1: Simple Back

Bet: Back Man City at 2.0 with £100 Commission: 5%

Outcome	Gross	Commission	Net
City wins	+£100	-£5	+£95
City loses	-£100	£0	-£100

Example 2: Simple Lay

Bet: Lay Chelsea at 3.5 with £50 stake Liability: £50 × 2.5 = £125 Commission: 5%

Outcome	Gross	Commission	Net
Chelsea wins	-£125	£0	-£125
Chelsea loses	+£50	-£2.50	+£47.50

Example 3: Back-to-Lay Green-Up

Initial: Back Liverpool at 3.0 with £100 Liverpool price shortens to 2.0 Action: Lay at 2.0

Lay calculation for equal profit:

Lay Stake = (£100 × 3.0) / 2.0 = £150

Outcomes:

• Liverpool wins: £200 back - £150 lay = £50
• Liverpool loses: -£100 back + £150 lay = £50

Guaranteed £50 profit!

Common Exchange Strategies

Matched Betting

Step	Action
1	Back at bookmaker (with free bet)
2	Lay at exchange
3	Profit from free bet conversion

Trading Favorites

Scenario	Strategy
Backing drifters	Back if you expect price to shorten
Laying steamers	Lay if you expect price to drift
News trading	React to team news before odds adjust

In-Play Trading

Timing	Opportunity
Pre-kick	Position before match
Early goal	Prices shift dramatically
Half-time	Reassess and trade

Common Back-Lay Mistakes

1. Forgetting Commission

Mistake: Calculating profit without commission Problem: Actual profit 2-5% lower Fix: Always factor commission into calculations

2. Liability Confusion

Mistake: Thinking lay stake = total risk Problem: Liability is stake × (odds - 1) Fix: Use calculator for lay liability

3. Over-leveraging

Mistake: Laying at high odds with small bankroll Problem: Large liability from small stakes Fix: Match liability to bankroll management rules

4. Poor Timing

Mistake: Entering trades without price movement expectation Problem: Commission eats into marginal trades Fix: Trade when expecting significant movement

Frequently Asked Questions

What's the difference between back and lay?

Back = betting FOR something to win (traditional). Lay = betting AGAINST it (you act as bookmaker, accepting risk if it wins).

Why would I lay a bet?

To trade positions (back-to-lay), hedge existing bets, or if you believe something won't win.

What is liability?

The amount you risk when laying. If your lay loses (selection wins), you pay liability. Liability = Stake × (Odds - 1).

How do exchanges make money?

Commission on winning bets, typically 2-5%. Unlike bookmakers, they don't set odds—users set their own.

Can I lay on Betfair?

Yes, Betfair is the largest betting exchange. You can back or lay any market where there's liquidity.

What happens if no one matches my bet?

Unmatched bets remain open until cancelled or matched. In low-liquidity markets, you may need to take worse odds.

Advanced Concepts

Greening Up (Equal Profit)

Method	Formula
Green Back	Lay at shorter odds than backed
Green Lay	Back at longer odds than laid
Equal split	Calculate for identical P/L

Dutching vs Laying

Aspect	Dutching	Laying
Where	Traditional books	Exchanges
Action	Back multiple	Oppose one
Risk	Win if any hits	Lose if selection wins

Arbitrage with Exchanges

Use exchange odds against bookmaker odds:

Book A	Exchange Lay	Arbitrage?
3.0	2.8	Yes
3.0	3.1	No

Pro Tips

• Factor commission always: It affects every calculation

• Start with low liability: Learn with small lay stakes

• Watch liquidity: Unmatched bets tie up funds

• Trade in-play carefully: Odds move fast; mistakes are costly

• Compare exchanges: Lower commission = better margins

Related Calculators

• Lay Bet Calculator - Lay-specific
• Betfair Commission Calculator - Commission details
• Matched Betting Calculator - Free bet conversion
• Arbitrage Calculator - Cross-market arbs
• Hedge Calculator - Lock in profits

Conclusion

Back and lay betting on exchanges gives you bookmaker-like capabilities. Our calculator handles liability, commission, and trade calculations for any back-to-lay or lay-to-back scenario. Understanding both sides of exchange betting opens trading strategies impossible with traditional bookmakers.

Calculate Your Back-Lay Bets Now →

The exchange model—backing and laying—creates opportunities traditional betting can't match. Master the mechanics, factor commission, and start trading positions for locked-in profits.