Nous utilisons des témoins (cookies) pour comprendre comment les visiteurs interagissent avec EdgeFox. Aucune donnée personnelle n'est collectée.

Sports Betting Variance Calculator

Run thousands of simulated betting sequences to see exactly what your profit and downside look like with your edge, bet size, and bet count. Free, instant, no signup required.

True win probability: 55.0%. Typical sharp bettors run 2–6% EV.

+$1,500
Median Profit
-$1,364
Worst Case (5%)
+$4,173
Best Case (95%)
21.4%
Loss Probability

20 Sample Bettors

EV
70% confidence interval
BEST
WORST

20 simulated bettors with identical 5% EV. Blue is the luckiest, red the unluckiest, and the green band is where 70% of bettors finish. Hover any line to see its profit at that point.

0618304254667890102120138156174192210228246264282300Bet #-$3.5k-$1.4k+$550+$2.5k+$3.5k

Variance in Numbers

The math broken down. Expected profit, the size of normal swings, the chance you finish in the red, and how big your bankroll needs to be to survive variance.

Expected Value per bet
Your 5% EV applied to your bet size.
+5.00% (+$5 per bet)
Average Odds
The American odds you entered, converted to decimal.
-110 (1.909 decimal)
True Win Probability
Derived from your EV and the odds you entered.
55.00%
Number of Bets
The sample size you're simulating.
300
Expected Profit
Mean profit if you placed 300 bets at 5% EV. This is your average outcome — but the variance below tells you how far you'll usually deviate from it.
+$1,500
Standard Deviation after 300 bets
The typical swing range. Roughly 68% of outcomes land within ±1 standard deviation of your expected profit.
±$1,645
(±$5.48 per bet avg)
70% Confidence Range
70% of bettors with these inputs will finish somewhere in this range. There's a 15% chance you finish below it and 15% chance above.
[-$211, +$3,211]
95% Confidence Range
The realistic worst-to-best case. Only 5% of bettors fall outside this range — split between the very lucky and the very unlucky.
[-$1,724, +$4,724]
Probability of Net Loss after 300 bets
The chance you finish in the red despite a positive EV. High over short samples, low over long ones.
18.09%
Recommended Bankroll for <5% Risk of Ruin
The minimum bankroll size that keeps your probability of going broke below 5% under continuous betting at this stake.
$2,702 (27 units)

Want EdgeFox to manage your bankroll automatically and surface +EV bets in real time?

Try EdgeFox Free →

Why variance matters more than your edge

Two sports bettors can have identical 3% edges and identical 1,000-bet samples, yet finish a year tens of thousands of dollars apart. That gap is variance. It's not skill, it's not bad luck, it's just math doing what math does over a finite sample.

Most bettors fail not because they pick wrong, but because they underestimate how rough the road gets even when they're picking right. The simulator above turns that abstract risk into concrete numbers: the size of your worst likely drawdown, the odds your bankroll busts before your edge compounds, and how many bets you actually need before your results mean something.

How to use this calculator

  1. Set the number of bets you plan to place over the period you're modeling.
  2. Enter your average odds. American odds. Most +EV signals fall between -130 and +140.
  3. Enter your EV %. Your expected return per dollar staked. 2-4% is typical for serious +EV bettors. The calculator derives the underlying win probability from your odds and EV.
  4. Enter your bet size in dollars. Use whatever you actually plan to risk per bet.
  5. Run the simulation and read the fan chart. Profit on the Y axis, bet number on the X. The dashed orange line is your expected value path. Blue is the luckiest of 20 bettors with the same edge, red is the unluckiest.

Understanding confidence intervals

The shaded bands on the chart show probability ranges. The middle 50% band tells you where your bankroll most likely lands. The outer 90% band shows the realistic worst and best cases. There's still a 5% chance you finish below the bottom band, which is exactly why bankroll management matters.

What is risk of ruin?

Risk of ruin is the probability that your bankroll drops below the level where you can no longer place even a single unit-sized bet. With proper sizing (1-2% units and a real edge), risk of ruin should be well under 5%. Increase your unit size or take negative-EV bets, and that number balloons fast.

The takeaway: a real edge plus disciplined sizing is the only thing that survives variance. Without both, you're gambling.

How many bets to confirm your real ROI?

Short answer: more than you think. With a 3% true EV and standard variance, you need roughly 5,000 to 10,000 bets to be 95% confident your observed ROI is within ±1% of your true EV. At fewer than 1,000 bets, your sample is mostly noise.

This is why short-term results, good or bad, are misleading. Run the simulator with your actual bet count to see how wide your true edge could be given your sample.

Flat betting vs Kelly Criterion

Flat betting means staking the same percentage of bankroll on every bet. It's simpler, less volatile, and recommended for beginners. The downside: you're not maximizing growth.

The Kelly Criterion sizes each bet proportional to your edge. Full Kelly maximizes long-term growth but produces wild swings. Most professional sports bettors use Quarter or Half Kelly, capturing most of the growth benefit with much smaller drawdowns.

Why sportsbook limits matter

This calculator assumes you can always bet your unit size. In reality, sharp +EV bettors get limited or banned at most sportsbooks within months. The practical solution is bet distribution: spreading your action across many books to stay under the radar at each. EdgeFox is built for exactly that, surfacing +EV opportunities across every major book in real time.

Frequently Asked Questions

What is variance in sports betting?+

Variance is the natural fluctuation around your expected return. Even with a real edge, your bankroll will go up and down because each individual bet outcome is random. Variance is what separates short-term luck from long-term skill.

Why does my ROI swing so much even when I bet +EV?+

Sports betting is a high-variance game. With odds around -110 to +110, even a great bettor with a 3% edge will see losing months. The math only converges over thousands of bets. This calculator shows you exactly what those swings look like.

How many bets do I need to confirm my real ROI?+

For a typical +EV bettor with a 3% EV and standard variance, you need around 5,000 to 10,000 bets to be 95% confident your true ROI is within ±1% of your observed results. Anything less is largely luck.

What is risk of ruin in sports betting?+

Risk of ruin is the probability that your bankroll drops below the level where you can no longer place a single unit-sized bet. A 5% risk of ruin means 1 in 20 bettors with your stats will go broke before their edge can compound. Reducing your unit size or fractional Kelly stake size lowers this risk.

How big should my sports betting bankroll be?+

A common rule for +EV bettors is 50 to 100 units, where each unit is 1-2% of bankroll. For Quarter Kelly with a 3% edge at -110 odds, you should hold at least 50 units. Run the calculator with your actual win rate and odds for a precise answer.

Should I use flat betting or Kelly Criterion?+

Flat betting is simpler and lower variance. Full Kelly maximizes long-term growth but with extreme swings. Most professional bettors use Quarter or Half Kelly as a compromise: meaningful growth with manageable variance.

What counts as a normal downswing?+

For a +EV bettor at 3% EV using 2% flat units, a 20-30% drawdown over 1,000 bets is completely normal. Drawdowns of 40%+ happen but are less common. Use the simulator to see how often each level of drawdown is expected to occur.

Is this calculator accurate for parlays and player props?+

The math is format-agnostic, but you must input the correct average odds and win rate. Parlays have different odds distributions and correlations, so accuracy depends on your inputs. The simulator assumes independent outcomes.