AUOdds

Surebet Calculator: How to Fix a Lock When a Stake Gets Limited

By the AUOdds team · Updated 9 Nov 2026 · 8 min read

Key takeaways
  • When one leg is limited, the accepted stake times its odds becomes the new target return, and every other stake is that target divided by its own odds.
  • If you've already placed the other legs, a top-up at a second bookmaker only keeps the lock if its price clears a break-even figure you can calculate before betting.
  • The same target-return method works for markets with four or more outcomes, and the lowest capped return sets the target.
  • Round stakes to whole dollars, then check the worst-case return still covers your total outlay, because coarse rounding can quietly break a lock.
  • Prices move, stakes get limited, bets can be voided and mistakes happen, so recheck every number before you place anything.

A surebet calculator is easy to use when every stake is accepted in full, but that isn't how betting with Australian bookmakers always goes. You request $500 on one leg and the bookmaker takes $300, or it offers a smaller amount than you asked for. Most calculators that rank for this search are built for overseas markets and assume full acceptance, so they leave you guessing at the exact point where you need help. This guide shows how to re-size the other legs so the lock still returns the same amount at the prices shown. It covers legs you've already placed, markets with four or more outcomes, and rounding stakes to whole dollars without breaking the maths. Every example uses decimal odds and Australian dollars.

In this guide
  1. Why does a surebet calculator break when a stake gets limited?
  2. How do you re-size the other legs after a part-accepted stake?
  3. What if you've already placed the other leg?
  4. How does a sure bets calculator handle four or more outcomes and caps?
  5. How should you round stakes without breaking the lock?
  6. What should the best arbitrage calculator do when a stake is capped?

Why does a surebet calculator break when a stake gets limited?

Most surebet calculators ask for the odds and a total bankroll, then split that bankroll so each outcome returns roughly the same amount. The split assumes every stake you type in will be accepted in full.

In practice, Australian bookmakers can cap how much they'll take on a market, and some may accept only part of the amount you request. When that happens, the planned split is wrong. One leg is now smaller than it should be, so if that outcome wins you collect less than the other legs cost you. A lock that looked like a 1.4% return can turn into a losing position on one outcome.

The global calculators that dominate search results generally don't model this. They also tend to list overseas bookmakers rather than licensed Australian ones.

The fix needs one change in thinking: stop working from total bankroll and start working from target return.

That's the whole method. The sections below apply it to two-way markets, to legs you've already placed, to four-outcome markets and to rounding.

Before any of it, confirm you're dealing with licensed operators. ACMA explains how to check whether a gambling operator is legal to offer services to Australians (ACMA-LEGAL). A rebalancing calculation is only as reliable as the bookmaker paying out on it.

How do you re-size the other legs after a part-accepted stake?

Here's a worked example on a two-way, pre-match market.

Add the implied probabilities: 1 ÷ 2.08 = 0.48077 and 1 ÷ 1.98 = 0.50505. The total is 0.98582, which is under 1, so a lock exists at these prices. The return is 1 ÷ 0.98582 − 1, or about 1.44%.

The original plan with $1,000 total:

What actually happens: Bookmaker A accepts only $300 on Team 1.

Don't place Leg B at $512.32. Rebuild the lock from the accepted stake instead:

The percentage hasn't changed. Only the size of the lock has. That's the key point: a limit shrinks the dollar return, but it doesn't have to break the lock, provided you haven't placed the other leg yet.

This is why order matters. Place the leg most likely to be limited first. That's usually the sharper price, or the bookmaker where your account has been capped before. Once you know what was accepted, size the remaining legs from that figure.

If the price on the remaining leg has moved by the time you get to it, recalculate with the new odds before betting. A lock exists only at the prices shown.

What if you've already placed the other leg?

Sometimes the order goes wrong. You placed Leg B in full at $512.32, then Bookmaker A accepted only $300 on Leg A. Now the position is unbalanced:

If Team 1 wins, you're down $188.32. The fix is a top-up on Team 1 at another licensed bookmaker.

Step 1: work out the return still needed. $1,014.39 − $624.00 = $390.39.

Step 2: find the break-even top-up price. The most you can add while keeping a lock is $1,014.39 − $812.32 = $202.07. The lowest acceptable price is 390.39 ÷ 202.07 = 1.932.

That gives a simple rule:

Minimum top-up odds = return still needed ÷ (target return − total already staked)

Step 3: compare it with what's on offer.

If no price clears 1.932, you're holding an unbalanced position, and you need to recognise that before deciding anything else. Don't chase the gap with larger stakes, and don't look for in-play options: online in-play sports betting isn't offered to Australians. Treat it as a lesson about leg order.

How does a sure bets calculator handle four or more outcomes and caps?

A sure bets calculator for multi-outcome markets uses exactly the same target-return idea. Each stake is the target return divided by that outcome's odds.

Take a four-outcome market spread across four bookmakers:

The implied probabilities are 0.28571 + 0.25000 + 0.23810 + 0.21739 = 0.99120. That's under 1, so the market locks at about 0.89%.

Plan with a $600 target return:

Now Outcome 2 is limited to $100. The new target is 100 × 4.00 = $400:

When more than one leg is capped, multiply each cap by its odds and use the smallest result as the target. Say Outcome 2 is capped at $100 (400 return) and Outcome 4 at $80 (80 × 4.60 = $368 return). The target becomes $368, because you can't lift Outcome 4 above its cap.

With four or more legs, the ordering advice matters even more. Place the legs at bookmakers most likely to limit you first, then size the rest. Each extra leg is another chance for a price to move or a stake to be cut, so keep the calculation open until the last bet is confirmed.

How should you round stakes without breaking the lock?

Stakes like $86.96 can look unusual on a betting account, and some punters prefer round figures. Rounding is fine, but it changes the returns, so you have to check the result.

Using the capped four-outcome example above, round to the nearest dollar:

The lock survives. Now round to the nearest $5 instead:

If Outcome 4 wins, you lose $4. Coarser rounding pulled that leg too far from its ideal stake.

A practical rounding checklist:

Thin margins leave little room. On a 1% lock with a $400 target, the whole buffer is about $4, so rounding a single leg by $5 can wipe it out. For more on whole-dollar staking, see the existing guide on rounded A$ stakes.

What should the best arbitrage calculator do when a stake is capped?

If you're comparing tools, the best arbitrage calculator for Australian conditions is the one that handles what really happens at the bookmaker. Use this checklist:

A calculator works with whatever odds you type in. Lock alerts approach the problem from the other end. AUOdds alerts list the exact stake for each outcome at the prices shown, so you start from a balanced plan. If a bookmaker then limits a leg, you apply the target-return method above to re-size the rest. If any price has changed by the time you bet, the original stakes no longer apply, so recalculate first.

For context, AUOdds data shows 188 locks over the last 30 days across Australian bookmakers covered, with a typical lock of about 1.4%. Margins that thin explain why careful rebalancing and rounding matter so much.

Be honest about the risks. Prices move. Stakes get limited. Bets can be voided under bookmaker terms. Typing 1.89 instead of 1.98 can turn a lock into a loss. No calculator removes those risks. It only makes the maths clearer.

Betting is for adults 18+ only. If it stops feeling like a controlled hobby, BetStop lets you self-exclude from licensed online bookmakers (BETSTOP, ACMA-BETSTOP), and Gambling Help Online offers free, confidential support. The Department of Social Services also lists gambling support information (DSS-GAMBLING).

Frequently asked questions

What is a surebet calculator?

It's a tool that takes the odds for every outcome in a market and works out how much to stake on each so that every result returns about the same amount. If the implied probabilities add up to less than 1, the stakes lock in a return at the prices shown. Most basic versions assume each stake is accepted in full.

How do I re-size stakes when a bookmaker limits one leg?

Multiply the accepted stake on the limited leg by its odds. That's your new target return. Divide the target by the odds on each other leg to get its stake. The percentage margin stays the same, but the dollar return shrinks. This works best when you place the leg most likely to be limited first.

What if I've already placed the other leg in full?

Work out the return still needed on the short leg, then find the break-even top-up price: return still needed divided by (target return minus total already staked). If another licensed Australian bookmaker offers that price or better, a top-up keeps the lock. If not, you're holding an unbalanced position.

Does rounding stakes really matter on a lock?

Yes. Typical margins are thin, so rounding a stake by $5 can push one outcome's return below your total outlay. Round to whole dollars, never round a capped leg up, then multiply each stake by its odds and confirm the lowest return still covers everything you've staked before placing the bets.

Sources

  1. Check if a gambling operator is legal, Australian Communications and Media Authority
  2. BetStop, Australian Government
  3. BetStop: the National Self-Exclusion Register, Australian Communications and Media Authority
  4. Gambling, Department of Social Services

More guides

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.