← Blog · 📝 Article · 10 November 2026

Order Book Depth on Betfair: How to Read It for Horse Racing

Order Book Depth on Betfair: How to Read It for Horse Racing

Order book depth on the Betfair Exchange is the amount of unmatched money waiting at each price on a runner’s ladder, on both the back and lay sides. It tells you how much you can bet at a price right now, and how far your stake would push the price if it were larger than the money on offer. In horse racing it matters most in the last 30 minutes before the off, when most of the money arrives.

This guide explains what the order book shows, how to read it, how depth changes as a race approaches, what it can and cannot predict, and how we use the same thinking when we publish lay signals.

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TL;DR

Table of Contents

What an order book is on the Betfair Exchange

The Betfair Exchange lets customers bet against each other rather than against a traditional bookmaker. By matching customers instead of taking the risk itself, it offers the option to lay, which means betting on something not to happen. On one side are backers, who think a horse will win. On the other are layers, who think it will not.

A bookmaker quotes you a price and takes your bet. On an exchange, nobody quotes a price for you. Prices are set by the orders customers place, and the order book is the list of those orders that have not yet been matched.

The order book is also called the price ladder. It shows the money waiting to be matched at every price on both sides of the market. The back column (blue) shows prices you can back at, funded by layers waiting to be matched. The lay column (pink) shows prices you can lay at, funded by backers waiting to be matched.

For developers, the structure is the same. Each side is a list of price and size pairs representing unmatched orders, and the Streaming API delivers them as available-to-back and available-to-lay data, either as a full ladder or as updates to it.

Depth versus matched volume

People often mix these up. Depth is how much money sits at each price down the ladder at this moment. Matched volume is what has already left the shelf. A large matched total can sit beside a thin ladder at your price: the market has traded, but that does not mean money is waiting at the price you want.

A simple rule: matched volume tells you how busy the market has been. Depth tells you what you can do next.

How to read the ladder

In the standard Betfair view, the blue column and the two columns to its left show what is available to back, and the pink column and the two to its right show what is available to lay. The bold number is the odds. The number underneath is how much of your bet should be matched instantly at that price.

Each runner shows three levels on each side. Here is how to interpret them:

Ticks are not even

Betfair prices must be valid exchange ticks, and the increment changes at fixed price boundaries. Increments are narrow at short odds and wider at long odds. A one-tick spread at 2.0 is a very different gap in percentage terms from a one-tick spread at 20. Always read depth together with the tick size at that price.

What happens when your stake is bigger than the best price

If your stake exceeds the money at the best price, the rest of the bet fills at the next prices down the ladder. Your average price ends up worse than the one you first saw. This is why depth matters even if you never trade the ladder: it tells you how much a given stake will cost you in price.

A quick check before placing a bet: add up the money at the best price and the next two levels. If your stake is a large share of that total, expect to move the market, or split the bet and work it over time.

What depth tells you about a horse racing market

Horse racing is the market where depth habits matter most, because liquidity varies so much between races.

A UK Group 1 race with £2m matched two hours before the off is highly liquid, while a minor hurdle with £30,000 matched is thin. In high-volume markets, price movements are more meaningful. In low-volume markets, a single large bet can move the price without reflecting any real information.

What depth tells you about a horse racing market

Approximate matched volumes in the 30 minutes before the off range from over £18m on the Cheltenham Gold Cup win market to around £60k for a Wolverhampton Class 5 all-weather race. The same source notes that £500 will not move prices at Cheltenham, but at a Wolverhampton Class 5 the same bet can move the price four to eight ticks against you.

Festival weeks change the picture again. During Cheltenham, Aintree and Royal Ascot weeks, pre-race matched volume is three to five times normal, and spreads are consistently one tick from 30 minutes before the off.

Race type Typical depth in the final half hour What it means for you
Festival or Group 1 Millions matched Stakes of a few hundred pounds barely move the price
Saturday Class 1 hurdle Around £1.4m matched Comfortable for most stakes
Weekday Class 3 handicap Around £280k matched Fine for modest stakes, watch the second level
Class 5 all-weather Around £60k matched A few hundred pounds can shift the price several ticks

The figures in the table are approximate matched volumes from the source above, so treat them as a guide to scale rather than a guarantee for any single race.

How depth changes as the off approaches

Depth is not static. It builds on a predictable pattern.

An academic study of UK to-win markets using Betfair data from 2014 to 2016 found that from the tenth minute before the race to the official start, average trading volume rose about 4.2 times, average liquidity about 3.4 times and average volatility nearly 1.6 times. The same study describes the final ten minutes as a closed system where price moves follow supply and demand from internal trading data.

Pre-race increases in volume liquidity and volatility

Practitioners describe the same shape. Participation is thin until five to ten minutes before the scheduled off, then builds rapidly as larger players arrive. A signal generated early in a thin market has less predictive value than the same signal two minutes before the off, when a market may have £500,000 matched.

One practical framework splits the 30-minute window into three phases:

  1. Off minus 30 to minus 15 (build-up): spreads are sometimes two to three ticks and money is still arriving.
  2. Off minus 15 to minus 5 (sharp): the main window, with deeper books and tighter spreads.
  3. Off minus 5 to the off (late): volatile, so smaller stakes make sense.

The pre-race scalping guide that sets out these phases also advises being flat by two minutes before the off. For pre-race bettors the lesson is simple: the book at 30 minutes out and the book at five minutes out can look like two different markets.

When the race starts, the picture ends abruptly. At the start, remaining orders are withdrawn and the book collapses rapidly. Volume in the pre-race period concentrates in a tight band of three to five ticks around the last traded price.

Where in-play delay fits

If you bet before the off, you are not affected by the in-play delay, and it shapes how we think about timing. We cover that in more detail in our piece on the Betfair in-play delay and pre-race lay strategies.

Can depth predict price moves or winners?

The most common use of depth is weight of money (WoM). It compares unmatched back money with unmatched lay money near the current price. More unmatched lay money than back money suggests the price will shorten, and more unmatched back money suggests it will drift.

One developer-oriented write-up gives the calculation as total back available divided by total back plus total lay available. Above 0.5 means more money wants to back than lay. Below 0.5 is the reverse. It also notes that a naive WoM figure on its own is noisy and easily distorted by a single large order, but as part of a composite signal from the full ladder it can be a useful short-term indicator.

Look beyond the top three levels

Most implementations use only the top three levels of the book. The full ladder tells a more complete story: the shape of liquidity beyond the top three levels shows where traders are positioning and where large orders are waiting. A wall of lay money several ticks above the best lay price suggests the market expects the price to shorten.

Large volume at a price can also act as a barrier. If £50,000 is available to lay at 3.0, the price is unlikely to move through it quickly, because the market has to work through all of that money first.

Keep expectations realistic

Depth gives you information about price direction, not about the winner. Independent testing shows the same: in an illustrative example, an order-book imbalance predicted shortening in 57% of 400 cases, but the edge was only a few pence per £100 after 2% commission. The takeaway is to use depth as one input, alongside price history and a clear staking plan, and not as a standalone system.

That is also why we pair market data with historical strike rates. Our write-up on horse racing data analysis for lay bettors explains how we combine them.

Reading depth safely: what to watch for

Depth is useful when you treat it with care. These are the points that matter in practice.

A sensible checklist before you act on what the ladder shows:

  1. Check matched volume first. Is this a market with real money in it?
  2. Check the spread. One tick is healthy. Several ticks mean you pay to get in and out.
  3. Compare your stake to the money at the top three levels.
  4. Watch whether a big order stays put as the price moves towards it. If it vanishes, it was not support.
  5. Wait for the later phase of the window when the market is more reliable.

If you are new to exchanges, our guide to three pre-bet checks for betting exchange beginners walks through the basics before you place your first lay.

Depth and lay betting

Laying means you are the one offering odds. Your liability is the stake multiplied by the odds minus one, so a lay at 5.0 risks four times your stake. Depth matters here in two ways. First, you need enough back money waiting at your price to get matched. Second, your price should not drift so far from the signal price that the liability no longer fits your plan.

That is why we favour mid-range prices. Our article on the 2.0 to 6.0 odds band and liability caps explains the reasoning, and our piece on laying the field with liability caps shows how to size stakes.

The exchange and the market it creates also differ by sport. UK and Irish racing produces 35 to 90 races per day with strong pre-race liquidity, which is why it suits a daily lay routine better than most markets.

Our perspective

Depth is the part of the market that tells you whether a price is real. A signal that looks good on paper is worth little if the money is not there to take your lay at the price we published.

That is why our approach starts with data, not opinion. We combine historical strike rates with live market prices to identify the runner we think is most likely to lose, and we publish every signal before the race so the record can be checked afterwards. Results are tracked and made permanently available. We report wins and losses alike, because transparency is the whole point.

We also built the service around how exchange bettors actually work. The dashboard links straight to the Betfair Exchange, so you can check the ladder at the moment you place the bet. Staking tiers help you size a lay against your own liability limit, and real-time alerts by email and Telegram mean you see a signal while the market still has time to build. For those who use trading software, API access lets you pull signals straight into your own setup.

Our view is simple. Use depth to decide how and when to place a bet, and use data to decide which runner to oppose. The two work best together.

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Try the signals alongside your own ladder reading

DonkeyRadar has a free tier with daily lay signals, so you can compare what we publish with what you see on the ladder. Pro costs £29 per month and adds real-time alerts by email and Telegram, full results history and API access. The paid plan starts with a seven-day trial.

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You can see both plans and start on the DonkeyRadar home page. If alerts matter to you, our guides to Betfair trading alerts and horse racing tips on Telegram show how they work in practice. You must be over 18 to bet, and you should only stake money you can afford to lose.

FAQ

What is order book depth on Betfair?

It is the amount of unmatched money at each price on both sides of a runner’s market. The back side is funded by layers waiting to be matched, and the lay side by backers waiting to be matched. Depth shows what you could bet right now, while matched volume shows what has already traded.

How do I see depth on the Betfair Exchange?

Open a market and look at the three blue back prices and the three pink lay prices for each runner. The bold figure is the odds and the figure underneath is the money available, as Betfair’s help pages explain. The ladder view shows more levels in one column.

When is the order book deepest for horse racing?

In the last few minutes before the off. Trading volume and liquidity rise sharply from about ten minutes out, with volume up about 4.2 times and liquidity about 3.4 times in one academic study. Big festival races and busy Saturday cards are the deepest of all.

Can I trust the big numbers I see on the ladder?

Treat them with care. Orders can be pulled at any moment, so a large figure shows intent, not a guarantee. Look at whether it stays in place as the price approaches, and check matched volume as well.

What is a betting exchange and how does it differ from a bookmaker?

On an exchange, customers bet against each other and set the prices through their orders. A bookmaker takes the other side of your bet itself. The exchange makes it possible to lay, which means betting that something will not happen.

Sources