Guide · 6 min read
Rounding arbitrage stakes: what round numbers really cost
A stake calculator gives you amounts like €493.98 and €506.02. Most people would type €495 and €505. This guide shows what rounding does to a sure bet, how to choose a rounding step, and what rounding can and cannot do for you.
Updated 22 October 2026
Contents
Why exact stakes can stand out
A sure bet splits your total stake so that every outcome returns the same amount. The formula almost never produces a round number: a €1,000 sure bet at odds of 2.10 and 2.05 needs €493.98 on one side and €506.02 on the other.
Recreational bettors rarely type amounts like that. They bet €20, €50 or €500. Round stakes, mainstream markets and spreading bets across several bookmakers are normal betting habits, and ArbVantage supports all of them. They are also simply easier: a round number is faster to type on a phone and harder to mistype under time pressure.
What rounding does not do is make you invisible. Bookmakers look at far more than stake amounts, and accounts that win consistently get limited sooner or later. More on that below.
What rounding costs: the calculation
Once you round, the outcomes no longer return exactly the same amount. One side pays a little more, the other a little less. What you give up is the gap between the exact profit and the worst outcome after rounding.
1/2.10 + 1/2.05 = 0.47619 + 0.48780 = 0.96400, so the margin is about 3.7%. That is a generous margin, chosen to keep the numbers readable; most real sure bets are smaller.
Exact: €493.98 at 2.10 and €506.02 at 2.05. Either outcome returns about €1,037.35: +€37.35.
Rounded to €5: €495 at 2.10 and €505 at 2.05, still €1,000 in total. Outcome A returns 495 × 2.10 = €1,039.50 (+€39.50), outcome B returns 505 × 2.05 = €1,035.25 (+€35.25).
The worst case is now +€35.25 instead of +€37.35: rounding to €5 costs at most €2.10 here, and either outcome is still a profit.
| Stakes (A @ 2.10 / B @ 2.05) | Total | If A wins | If B wins |
|---|---|---|---|
| €493.98 / €506.02 (exact) | €1,000.00 | +€37.36 | +€37.34 |
| €495 / €505 (to €5) | €1,000 | +€39.50 | +€35.25 |
| €490 / €510 (to €10) | €1,000 | +€29.00 | +€45.50 |
| €500 / €500 (to €50) | €1,000 | +€50.00 | +€25.00 |
The coarser the step, the further the two outcomes drift apart. With a thin margin, the same rounding can push one side below zero. At odds of 2.02 and 2.00 (margin about 0.5%), the exact split of €1,000 is €497.51 / €502.49 and returns about +€4.97. Rounding to €500 / €500 gives +€10.00 if the first outcome wins and ±€0.00 if the second wins. Rounding to €490 / €510 gives −€10.20 if the first outcome wins: a loss. The thinner the margin, the finer you need to round.
Assumptions: decimal odds, both bets accepted in full at the stated odds and not voided, no betting fee, amounts rounded to the cent.
Why the average hardly moves
Rounding shifts profit from one outcome to the other, it doesn't destroy it. If the bookmakers' prices, with their margin removed, reflect the real chances, the average result of the rounded bet is the same as the exact one. In the €5 example: 0.494 × €39.50 + 0.506 × €35.25 ≈ €37.35, the same as the exact split.
That is an average over many bets, not a promise for one. On any single sure bet you get one of the two outcomes, so the number that matters for safety is the worst one. Keep the worst outcome positive and you keep the core idea of a sure bet intact.
The four rounding modes in the calculator
ArbVantage offers four rounding modes for every sure bet and in the manual calculator. The step grows with the stake, so small bets stay usable:
| Mode | Stake under €50 | €50 to €499 | €500 and more |
|---|---|---|---|
| Exact | €0.01 | €0.01 | €0.01 |
| Light | €0.50 | €1 | €5 |
| Natural | €1 | €5 | €10 |
| Heavy | €5 | €10 | €50 |
Each leg is rounded on its own, so in the example above "Natural" gives €495 (a €5 step, because the stake is under €500) and €510 (a €10 step). That is €1,005 in total, returning +€34.50 or +€40.50.
There is a safeguard: if your chosen mode would turn the sure bet into a loss, or cost more than about a third of its margin, the calculator falls back to the next finer mode and tells you it did. You can also choose to round only at bookmakers that limit, and keep exact stakes at exchanges and sharp books, where nobody cares about a stake of €506.02.
One-sided rounding: putting the profit on one side
Sometimes you want a round stake on one leg only. Fix that leg and solve the other to the cent. With €495 fixed at 2.10, outcome A returns €1,039.50; the other leg needs 1,039.50 / 2.05 = €507.07. Total €1,002.07, and both outcomes return about +€37.4.
You can also go further and place the whole profit on one outcome. Size leg B so that it only returns your total stake: B = 495 / (2.05 − 1) = €471.43. If B wins you get back exactly what you staked (±€0); if A wins you make +€73.07. Round B down to €470 and the B result becomes −€1.50, while A pays +€74.50.
This is a legitimate choice if you have a view on the match, but be clear what it is: one outcome now carries all the profit and the other carries none, or a small loss. It is no longer an equal sure bet. Small rounding of this kind is harmless; deliberately loading one side is closer to a value bet than to arbitrage.
Limits: rounding doesn't prevent them
Round stakes are a normal habit, and they make betting faster and less error-prone. They don't stop a bookmaker from limiting your account. Bookmakers judge accounts on many signals, above all whether you consistently take prices that turn out to be better than the market. Some of our own accounts have been limited, and yours may be too.
Our guide to bookmaker limits explains what a limit looks like, which habits are normal and what to do when it happens. For the stake maths behind every sure bet, see splitting your stakes, and if a price moves while you place your rounded stakes, what to do when one leg fails.
FAQ
What should I round my stakes to?
It depends on the stake and the margin. For stakes of a few hundred euros, €5 is a sensible step; above €500, €10 is common. The thinner the margin, the finer you should round, so the worst outcome stays positive.
Does rounding cost profit?
It moves profit from one outcome to the other. The worst outcome gets a little smaller and the best a little larger. In the example with €1,000 at 2.10 and 2.05, rounding to €5 costs at most €2.10.
Does rounding prevent bookmaker limits?
No. Round stakes are a normal betting habit and make placing bets easier, but nothing prevents limits. Bookmakers look at many signals, above all whether an account keeps winning against the market.
Sources
- Wikipedia: Arbitrage betting (stake split and margin)
- RIS: Gebührengesetz 1957, § 33 TP 17 (Austrian betting fee, which changes the effective odds)
As of October 2026. The calculations are illustrations under the stated assumptions. Not betting, legal or tax advice. 18+.
Betting involves risk, sure bets included: odds move, bets get voided and accounts get limited. Only stake money you can afford to lose. If betting stops being fun, our responsible gambling page lists free help in Austria and Germany.