Dutching Software: How to Find Whole-Field Racing Dutches Under 100%

By the AUOdds team · Updated 23 Oct 2026 · 8 min read

Dutching software is usually sold as a staking tool, but the version worth paying attention to does something harder: it finds Australian races where backing every runner, each at its best price across different bookmakers, adds up to less than 100%. That is the difference between tidy staking on a guess and a lock at the prices shown. This guide separates the two kinds of dutching and walks through a real-looking eight-runner field book with per-runner stakes. It also sets out what software has to do to find these fields: scan many bookmakers, follow scratchings and keep prices fresh. You will also see where a dutching calculator app fits, and the risks that remain even when the numbers look right.

What does dutching software actually do?

Most products sold as dutching software do one simple job. You pick some runners, enter their odds and a total stake, and the program splits the money so each selection returns roughly the same amount. That is useful, but it is only arithmetic. It does not tell you whether the bet is any good.

There are really two different activities sharing one name.

• Selection dutching means backing two, three or four runners you fancy so that any of them winning pays about the same. The rest of the field is left uncovered.
• Whole-field dutching means backing every runner in the race, each at the best price available across several bookmakers, so whichever runner wins, you hold a winning ticket.

The first is a betting opinion with neat staking. The second only makes sense when the best prices combined add up to less than 100% implied probability. When they do, the race becomes a lock at the prices shown, much like a two-way arbitrage on a tennis match, just with more legs.

Much of what ranks for this topic is built for the first job: strike-rate systems, race-predictor tools and stand-alone calculators that have not changed in years. They assume you already have a view on the race and want help staking it.

Software for whole-field dutches needs a different engine. The staking maths is easy. The hard part is spotting the brief moment when the best price on every runner, often taken from four or five different bookmakers, prices the whole field under 100%. That search, and what it takes to do it properly, is the focus of the rest of this guide.

Why is selection dutching a gamble when a whole-field dutch is not?

Selection dutching evens out your outcomes across your chosen runners. It does not change the odds of being right.

Say you like three runners in a ten-horse race at 3.50, 5.00 and 8.00. Their implied probabilities are 28.6%, 20.0% and 12.5%, which is 61.1% combined. Split $100 so each pays the same:

• $46.78 at 3.50
• $32.75 at 5.00
• $20.47 at 8.00

If any of the three wins, you collect about $163.70, a profit of roughly $63.70. If any of the other seven runners wins, you lose the full $100. The calculator made the result even across your picks. It did not make the bet favourable. Whether it pays off over time depends entirely on whether your selections win more often than 61.1% of the time.

A whole-field dutch removes the opinion. Every runner is covered, so the only question is price. A single bookmaker's field almost always adds up to well over 100%, because that margin is how a bookmaker earns its living. But bookmakers price runners differently. One might be generous on the favourite, another on a roughie, a third on the second favourite.

Take the best price for each runner from wherever it sits, add up the implied probabilities, and every so often the total dips under 100%. Only then does a whole-field dutch lock in a return. Above 100%, backing the whole field simply guarantees a small loss, which is why good software discards those fields rather than showing them.

What does an under-100% field book look like?

Here is a worked example of an eight-runner race, using the best fixed-odds price for each runner across five licensed bookmakers, labelled A to E.

• Runner 1: 2.90 at Book A (34.48%)
• Runner 2: 4.20 at Book C (23.81%)
• Runner 3: 6.50 at Book B (15.38%)
• Runner 4: 10.00 at Book E (10.00%)
• Runner 5: 15.00 at Book A (6.67%)
• Runner 6: 26.00 at Book D (3.85%)
• Runner 7: 41.00 at Book C (2.44%)
• Runner 8: 67.00 at Book B (1.49%)

The implied probabilities total about 98.12%. Because that is under 100%, the field can be dutched for a return of roughly 1.9% at these prices.

To stake $500, divide 500 by 0.9812 to get a target return of about $509.57, then divide that by each runner's odds:

• Runner 1: $175.71
• Runner 2: $121.33
• Runner 3: $78.40
• Runner 4: $50.96
• Runner 5: $33.97
• Runner 6: $19.60
• Runner 7: $12.43
• Runner 8: $7.61

Total outlay is $500.01. Whichever runner wins, the return lands between about $509.55 and $509.87, so roughly $9.55 is locked in at the prices shown.

Two details matter. First, round to the cent where you can. Rounding Runner 7 down to a flat $12 would drop its return to $492, below your outlay. Second, notice the size of the small stakes. Runner 8 needs only $7.61, but if Book B has moved that price to 51.00 by the time you get there, the field may no longer be under 100%. This is why speed and live prices matter so much.

What should dutching software do to find these fields?

A calculator waits for you to bring the prices. Software that finds whole-field dutches has to go and get them, constantly. Here is a checklist worth holding any tool to.

• Scan many bookmakers. The more licensed Australian books it covers, the more chances of a soft price on each runner. Under 100% fields usually need the best price from several different books at once.
• Only use licensed operators. You can check any bookmaker against the ACMA's register of legal operators before you open an account.
• Match runners correctly. Different books format names, barrier numbers and saddlecloth details differently. A mismatch means a wrong book.
• Follow scratchings and emergencies. A late scratching changes the field. The software should recalculate immediately and drop the alert if the book no longer works.
• Update live. Prices shift right up to the jump. Old prices produce false locks.
• Show per-runner stakes and the book for each. You should see exactly how much to place on each runner and where, plus the worst-case return after rounding.
• Stick to pre-race fixed odds. Bets are placed online before the jump, not during the race.

Scale matters here. In AUOdds data, the service tracks about 15,000 prices at any moment across 9 bookmakers, with prices typically about 10 seconds old. Across all the markets it monitors, it flagged 2,666 locks in the last 30 days and 1,382 in the last 7 days, with a typical lock of about 1.5%.

That typical figure is a useful reality check. Most locks are small, so a tool that regularly shows 5% or 8% racing books is probably working from stale prices, or it has missed a scratching.

Is the best dutching calculator app enough on its own?

A good dutching calculator app is worth having, but it solves a different problem. It tells you how to stake a field once you know the prices. It cannot tell you which race, right now, has a combined book under 100%.

If you are comparing options for the best dutching calculator, look for:

• Entry for eight to twenty runners, not just two or three
• A running total of implied probability, shown clearly as a percentage
• Stakes to the cent, with a check that every outcome covers your outlay
• A choice between a fixed total stake and a fixed target return
• Clear handling when you remove a scratched runner

The best dutching calculator app with all of those features is still only as good as the prices you type in. Checking eight runners across nine bookmakers by hand means comparing 72 prices, and several will have moved by the time you finish. Fields under 100% tend to be brief, so manual searching mostly finds books that were under 100% a minute ago.

That is where scanning software and a calculator work together. The scanner, such as the alerts AUOdds sends members, flags a field and the stake for each runner. Your own dutching calculator app then gives you an independent check before you place anything. If the two disagree, stop and find out why. A one-digit typo on a 41.00 runner can quietly turn a lock into a loss.

In short, the calculator handles the maths and the software handles the search. For whole-field racing dutches, the search is the part that decides whether there is anything to stake at all.

What risks remain, and how do you stay in control?

A whole-field dutch locks in a return at the prices shown. It does not protect you from everything that can happen between the alert and the jump.

• Prices move. With eight or more bets to place, one price shortening can push the field back over 100%. Place the biggest stakes and the most volatile prices first, and recheck the total as you go.
• Stakes get limited. A bookmaker may accept only part of a bet, leaving one runner under-covered. Decide in advance what you will do if that happens.
• Bets can be voided. Palpable errors, late scratchings and each bookmaker's own rules can change or cancel a leg. Read the racing rules for every book you use.
• Mistakes happen. Wrong runner, wrong race, wrong stake. Slow down and double-check each slip.
• Capital is tied up. A $500 dutch for a $9 lock needs money spread across several accounts at once.

On tax, the ATO's Taxation Ruling IT 2655 sets out how gambling winnings are treated and when betting activity may amount to a business. Read it, keep simple records of every leg, and get professional advice if you are unsure about your situation.

Finally, a short reminder. Betting is for adults 18 and over. Keep a budget, never chase losses, and treat any locked return as a small, uncertain margin rather than income. If betting is causing stress, BetStop, the National Self-Exclusion Register, lets you block yourself from all licensed Australian online bookmakers, and Gambling Help Online offers free, confidential support around the clock.

Frequently asked questions

Sources

1. Check if a gambling operator is legal, Australian Communications and Media Authority
2. Taxation Ruling IT 2655: gambling and betting winnings, Australian Taxation Office
3. BetStop: the National Self-Exclusion Register, Australian Communications and Media Authority
4. BetStop, Australian Government

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• Horse Racing Dutch Betting Calculator: Scratchings Fixes

18+ only. Betting involves risk, and prices and limits can change before you place a bet. If gambling isn't fun any more, Gambling Help Online (1800 858 858) is free and confidential, and BetStop lets you exclude yourself from every licensed Australian bookmaker.