期待値計算機

Free sports betting EV tool — see dollar EV, ROI % and +EV value in seconds

期待値（EV）とは？

Expected Value (EV) is the average profit or loss per bet if you could repeat the same wager thousands of times. In sports betting, positive EV means the price offered by the bookmaker is higher than your fair probability implies—often called a value bet. Negative EV means the line is against you even if you win occasionally.

Professional bettors separate luck from edge: they estimate true win probability from models, injuries, and market movement, then compare it to decimal odds. This free EV calculator instantly shows dollar EV and ROI so you can rank opportunities before staking.

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勝率をパーセンテージ（0-100）で入力してください

結果

Enter stake, odds and win probability — results update automatically.

この計算機の使い方

期待値（EV）計算機は、賭けが長期的に利益を生むかどうかを判断するのに役立ちます。

  • 賭け金額: 賭ける予定の金額
  • デシマルオッズ: ブックメーカーが提供するデシマル形式のオッズ
  • 勝率: 賭けに勝つと見積もった確率（0-100%）

正のEVは長期的に利益を生む賭けを示し、負のEVは利益を生まない賭けを示します。

ヒントとベストプラクティス
  • 徹底的な調査と分析に基づいて現実的な勝率を使用してください。
  • EV計算は完全な確率推定を前提としています。見積もりには慎重になりましょう。
  • 正のEVは短期的な利益を保証するものではありませんが、長期的な収益性を示します。
  • 資金管理を考慮し、失っても大丈夫な金額だけを賭けてください。

How Expected Value (EV) Works in Sports Betting

Every bet has a price (odds) and a true chance of winning. The bookmaker builds margin into the line so that, on average, bettors lose. Your job as a value hunter is to find spots where your estimated probability is higher than the implied probability from the odds. When that gap exists, EV turns positive and the bet is worth taking at the right stake size.

EV does not promise tonight’s result—it measures long-run economics. A +5% ROI bet can lose ten times in a row; over hundreds of similar wagers, profit should track the math if your probability model is calibrated. Combine EV with bankroll discipline and line shopping across books to compound small edges.

The core expected value formula for a single wager is:

\[ \text{EV} = (p \times \text{Profit}) - \bigl((1-p) \times \text{Stake}\bigr) \]

Where \(p\) is your win probability (0–1), Profit is stake × (decimal odds − 1), and Stake is the amount risked. ROI% ≈ EV ÷ Stake × 100.

\[ \text{Profit} = \text{Stake} \times (O - 1) \quad\text{where } O \text{ is decimal odds and } p \text{ is win probability as a decimal.} \]

Worked Example: Real Madrid vs Manchester United

Fixture: Real Madrid vs Manchester United — you back Madrid on the moneyline at a soft book.

Inputs for a +EV check (decimal odds)
Input Value A Value B / note
Stake / decimal odds$1002.50
Your win probability45%55% implied lose

Suppose stake $100, decimal odds 2.50, and you believe Madrid wins 45% of the time (not the 40% implied by 1/2.50).

Profit if win = \(100 \times (2.50 - 1) = \$150\). Then:

  1. EV = \(0.45 \times 150\) − \(0.55 \times 100\) = \(67.5 - 55\) = <strong>+\$12.50</strong>.
  2. ROI on stake ≈ 12.5% — a positive-EV bet if your 45% estimate is honest.
  3. If you had used the book’s implied 40% instead, EV would be zero—showing why your model matters.
  4. Enter the same numbers in the calculator above to verify and stress-test other odds formats.

Why Positive EV and Line Shopping Go Together

The same team can be +2.40 at one book and +2.55 at another. That 0.15 difference often flips EV from negative to positive without changing your analysis. Habitually comparing closing lines trains you to spot stale prices before limits tighten.

Track CLV (closing line value): if you consistently beat the closing number, your process is likely sound even during losing streaks. Pair EV screening with implied probability checks so you do not confuse big underdog prices with true value.

Build a Smarter Betting Workflow

After ranking +EV plays, size stakes with our Kelly criterion calculator so growth stays disciplined.

Convert any price into win probability using the implied probability calculator before you plug numbers here.

When books disagree sharply, also test arbitrage (surebet) scenarios—risk-free locks beat thin EV if execution is clean.

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Frequently Asked Questions

What is Expected Value (EV) in betting?

Expected Value is the average profit or loss per bet if you repeated the same wager many times. Positive EV means the odds are favorable relative to your true win chance; negative EV means the book has the edge. It is the foundation of professional value betting.

How do you calculate expected value in sports betting?

Multiply your win probability by profit if you win, then subtract lose probability times stake. With decimal odds O and stake S: Profit = S×(O−1), EV = p×Profit − (1−p)×S. Our calculator handles format conversion and ROI automatically.

What is a good expected value percentage?

There is no magic number—context matters. Many sharp bettors target +2% to +8% ROI per bet after realistic probability estimates. Tiny edges compound; chasing 20%+ EV often means overconfident models. Consistency and volume matter more than one flashy percentage.

Why is positive EV line shopping important?

Books set different prices on the same outcome. A line that is −EV at one shop can be +EV at another with identical analysis. Shopping lines is often the easiest way to increase EV without improving your model—just execution discipline.

Does positive EV guarantee short-term wins?

No. Variance is huge in sports betting—you can lose many +EV bets in a row. Positive EV only describes long-run expectation if your probabilities are accurate. Use proper bankroll management and track results over hundreds of wagers.