Step-by-step guide to entering stake, odds, and projected win probability so you can interpret EV, ROI, edge, and break-even correctly.
New to this? Start with:What Does -110 Mean?
You found Lakers +105 on DraftKings for tonight's game against the Celtics. It looks like a decent line — but is it actually worth your money? The +EV Calculator answers that question in about 30 seconds. Here is exactly how to use it.
A bet is +EV (positive expected value) when the sportsbook's price is better than the true probability of winning. You are getting paid more than the risk is worth.
Tip: +EV does not guarantee this one bet wins. It means the decision is profitable over many similar bets — like a casino that does not win every hand but always wins over time.
Set the amount you would actually risk. Start with $100 to keep the math easy, then adjust to your real stake size later.
Enter the sportsbook's price in any format — American, decimal, fractional, or implied probability. The calculator converts all formats automatically.
For our Lakers example: enter +105 in the American odds field.
The calculator instantly shows:
That 48.78% is the minimum win rate you need at these odds to break even.
This is the key input — your honest assessment of how likely the Lakers are to win.
Where do you get this number? Here is a practical workflow:
1. Start with a market baseline. Check a sharp sportsbook like Pinnacle. If Pinnacle has this game at -110 / -110, the no-vig probability is 50% for each side. That is your starting point.
2. Build your adjustment list. Factor in:
3. Adjust in small increments. If you see 2-3 percentage points of evidence favoring the Lakers, bump your estimate from 50% to 52-53%. Keep adjustments modest unless the signal is very strong.
4. Sanity check. If your number is far from the market consensus, double-check your assumptions. Markets are not always right, but they are a strong baseline.
For this example, let's say your analysis puts the Lakers at 53%. Enter that in the win probability field.
With Lakers +105, a $100 stake, and your 53% estimate:
| Output | Value | What It Means |
|---|---|---|
| EV Amount | +$8.65 | You expect to make $8.65 per bet on average |
| EV % | +8.65% | Expected return on every dollar wagered |
| Break-Even % | 48.78% | Minimum win rate to break even at +105 |
| Edge % | +4.22% | Your estimate (53%) minus break-even (48.78%) |
A positive EV amount confirms this is a +EV bet. The 4.22% edge means you have a meaningful advantage over the book's price.
Many bettors use a threshold to filter out thin edges:
Our Lakers example at +8.65% EV clears even a strict threshold. This is a bet worth taking.
Tip: The most common mistake is overestimating your win probability. If your 53% estimate is actually 50%, the EV flips to roughly +$2.50 — still positive but much thinner. Be conservative with your estimates, especially early on.
Same game, but now you are looking at Celtics -125 on a different book. Your model says Celtics win 55% of the time.
The EV is negative. Even though you think the Celtics are likely to win, the price does not offer enough value. Pass.
The +EV Calculator is only as good as your probability estimates. Track every bet:
Open the +EV Calculator and enter tonight's lines. Compare the edge across different sportsbooks to find the best price.
For the math behind each output, read Positive EV Betting Formula Explained. Use the Odds Converter to standardize price formats before evaluating edge.
You need stake, market odds, and your own estimated win probability. The tool calculates EV amount, EV percent, break-even rate, and edge.
EV percent is expected value divided by stake. It shows the expected return per dollar wagered in percentage terms.
Start with the market implied probability, then adjust for injuries, matchup style, schedule, and your model inputs. Keep notes and compare your projections to real results to calibrate over time.