Market Depth on Betfair Exchange: How Much Can You Really Bet?

What a £600 back meets on the way down

Picture a bettor backing £600 at 3.50, their only bet in the market, with every price and amount invented. The ladder shows £180 waiting at 3.50, £140 at 3.45 and £280 at 3.40: £600 in all, so the stake fills, but only if the worst price they accept is 3.40.

If it wins: £180 × 3.50 = £630.00, £140 × 3.45 = £483.00 and £280 × 3.40 = £952.00. That is £2,065.00 on £600, an average price of 2,065 ÷ 600 = 3.4417. A flat 3.50 would return £2,100.00, so the walk down the ladder costs £35.00 before exchange commission.

A stake filled down three prices is not new (the limits guide works one, and covers what else caps a bet besides the market). The new number is the average: the further it sits below your price, the less was waiting there.

The alternative is to take the £180 at 3.50 and leave £420 waiting at that price. Only the part that matches can ever attract exchange commission, and the calculator lets you price only the part that matched.

How to read a ladder before you size a bet

A ladder is the column of prices with the money waiting beside each. Read it before you touch the stake box, in this order.

1. The size at your price.

   Compare it with your stake. Enough, and you fill at once; not enough, and the rest is a choice.

2. The prices beside it.

   For a back, the lower ones; for a lay, the higher. Your stake reaches them only if you accept them, and the bigger it is against the queue, the further down it goes; their average is the price you really get.

3. The gap.

   No offer sits between the best price to back and the best price to lay; taking at once means paying across it.

4. The limits.

   A lay's liability, stake × (odds - 1), is what has to fit inside your limits, and the liability side of laying has the sums. Then work the liability out in a calculator.

What changes whether a bet fills

From Betfair's rules and newsletters, some archived copies: check the current terms for each.

Your settings. Best Price Execution is on by default, so a bet matches at improved odds if they appear after you place it. MatchMe is off by default; Betfair says it makes a bet easier to match within a pre-determined range, so check the range before you switch it on.

Matching across markets. Cross-selection and cross-market matching can fill you at a better price from offers on other selections or equivalent markets (Match Odds, Asian Handicap, Over/Under, Total Goals), provided the price sits on the ladder, and Betfair says it may generate a small amount of additional revenue from them. An older Betfair post describes football "liquidity pooling" into Draw No Bet and Double Chance.

Betfair itself. Its terms let it add liquidity occasionally on less liquid markets (clause 18.2.3), a stated exception and no promise that your market will fill. Cash Out may be unavailable when liquidity is low, so the exit you plan is a bet that needs an offer too.

The clock. In-play markets usually carry a delay of 1 to 12 seconds. Older archived newsletters put 90% of football matches at five seconds, and describe no delay on passive bets (those not taken immediately) rolling out sport by sport.

Betfair SP. Starting Price has its own minimum liability: £10 for a lay and £1 for a back at Betfair SP, or the currency equivalent. (Side note: Betfair Starting Price is calculated to six decimal places at the off; before then you see only a projection.)