How Saturday handicap overrounds compare to midweek markets
The introduction to overrounds piece makes the case for why the total book percentage matters. This one takes the matter a step further and puts numbers against the pattern: how tight or loose are different types of UK racing markets, and what does the pattern say about where a betting bank is best deployed? The answer, as you might expect from an argument that has been made about markets since the Victorian era, is that the level of competition between bookmakers does most of the work.
What the arithmetic is doing
To recap briefly: the overround of a market is the sum of the implied probabilities of every runner. A fair book — one with no bookmaker margin — would sum to exactly 100%. In practice every book is priced above 100%, and the excess is the bookmaker's theoretical edge. A market at 110% is charging 10p in the pound of margin; a market at 130% is charging 30p. Running any set of prices through the overround calculator takes about ten seconds and produces the figure directly.
What we are interested in here is not a single book but the pattern across race types. If you know, before you place a bet, that a given race sits in a category where the overround typically runs at 108% rather than 125%, that is information worth having. It does not change the result of any particular bet, but it changes the long-run economics of the type of bet you are placing, in much the same way that choosing the right end-odds of an each-way bet matters more than picking the right horse within any single bet.
The pattern across race types
The table below summarises typical overround ranges across the main categories of British and Irish flat and jumps racing. The figures are representative of what you will see in a competitive high-street book, averaged across the early- and mid-market period (the last ten minutes or so before the off). They are not precise measurements of any particular race, and individual examples will fall a little either side of the ranges given.
| Market type | Typical overround | Margin per £1 |
|---|---|---|
| Grade 1 / Group 1 championship race | 103–108% | 3p – 8p |
| Saturday ITV-televised handicap (10+ runners) | 105–112% | 5p – 12p |
| Festival handicap (Cheltenham, Royal Ascot, Goodwood) | 106–115% | 6p – 15p |
| Weekday Class 2 handicap | 110–118% | 10p – 18p |
| Weekday Class 4-5 handicap (major track) | 115–122% | 15p – 22p |
| Weekday Class 5-6 handicap (minor track) | 118–130% | 18p – 30p |
| Small-field non-handicap (4-6 runners) | 108–118% | 8p – 18p |
| Ante-post championship market (>30 days out) | 130–200%+ | 30p – 100p+ |
A few patterns jump off the table. The spread between the tightest race (a genuine Group 1 championship, where multiple major firms are competing intensely for a handful of runners) and the loosest in-running market (a minor midweek handicap at a small track) is something like twenty percentage points. That is a twenty-pence-per-pound difference in the fundamental economics of the market. Same sport, same punter, same calculator; very different propositions.
Why the gap exists
The orthodox explanation, which is basically correct, is that overround scales inversely with the degree of competitive pressure between firms on that market. A Group 1 championship race attracts every major bookmaker's attention and traders fight over the prices; a Class 5 handicap at Wolverhampton on a Tuesday evening is priced-up by a junior or by an algorithm with a generous margin baked in, and no-one is particularly incentivised to sharpen it unless significant money starts to arrive on a particular runner. The shape of the book is a direct reflection of how much attention the book has had.
A related factor is the information-content of the race. Group 1 championship markets are priced by people who genuinely believe they have an edge on the race's outcome; they price more confidently, at tighter margins, because they are willing to take on the exposure. Class 5 markets are priced defensively because the information-quality is lower and the bookmaker's confidence in any given price is weaker. Punters sometimes imagine the overround is the firm's profit target; it is better thought of as the firm's uncertainty premium.
A third factor, worth flagging for the ante-post numbers in particular, is the option value of non-runners. An ante-post market taken 30 days before a Festival race necessarily includes many horses that will not go to post on the day, for reasons ranging from injury to change-of-plan to ground preference. The bookmaker's overround on such a market is high partly because it compensates for having to quote fixed odds on horses that may never run at all. This is why the Festival ante-post markets sit at 130% or more, while the equivalent declared market two days before the race is down at 108%.
What to do with this information
Three practical consequences for anyone deploying a betting bank systematically.
First, the choice of which races to bet on matters more than punters typically realise. A punter who backs only Saturday feature handicaps and Group-class championship races is, mathematically, playing a very different game from one who bets every race on the card at a midweek meeting. Even if both are equally good at picking horses, the first will lose less to bookmaker margin over a year than the second by an enormous margin — multiple percentage points of turnover, which compounds ruthlessly over thousands of bets.
Second, ante-post has a legitimate place, but the case for it has to clear a much higher bar than the same bet taken on the day. A horse at 12/1 ante-post in a 200%-overround market is, in fair-odds terms, considerably shorter than a horse at 12/1 in a 108%-overround declared market. The apparent price is the same; the actual value is wildly different. Ante-post specialists who beat the market do so by correctly identifying horses whose prices are systematically under-estimated in the face of enormous non-runner risk — not by finding big prices in generally soft markets.
Third, small-field races deserve a second look. A non-handicap with four or five runners might sit at a 112% overround — not dramatically tighter than a competitive handicap, and often tighter than a midweek handicap. The bookmaker's margin in a small-field race is structurally constrained by the fact that the favourite's true chance of winning is already a substantial fraction of 100%, so the available room for padding is less. That is worth knowing, even if the races themselves do not always make for compelling betting heats.
How to check for yourself
None of this is particularly difficult to verify on any given weekend. Before the racing starts, pick three races of different types: one Saturday feature handicap, one weekday-equivalent handicap, and one small-field non-handicap. Open the bookmaker of your choice, write down the prices for every runner in each race, and run them through the overround calculator one by one. The three overrounds will almost certainly pattern-match the table above, and the exercise of having done it for yourself — rather than taking the pattern on trust — makes the lesson stick in a way that reading about it cannot.
The habit of glancing at the overround before placing a bet is, in the final analysis, the most valuable piece of market-reading that a betting punter can cultivate. It takes about ten seconds and it tells you, with arithmetic certainty, what fraction of the stake the house is charging you before any horse has left the stalls. Most of the other edges in this game are small and contested and hard-won. This one is free.