What Is +EV Betting?
A developer's guide to expected value in sports betting — the math behind finding bets with a genuine edge, with formulas and code examples.
+EV betting means placing bets where the sportsbook's odds imply a lower probability than the true likelihood of the outcome. The formula is: EV% = (fair_probability x decimal_odds - 1) x 100. If the result is positive, the bet has positive expected value — meaning it will be profitable over a large sample of bets. Fair probability is typically derived from Pinnacle's sharp lines with vig removed.
The Concept: Why Expected Value Matters
Every bet you place has an expected value — the average amount you'd win (or lose) if you made the same bet thousands of times. Casinos have a positive expected value on every game they offer; that's their business model. +EV betting flips this: you become the casino.
The key insight is that sportsbooks don't all agree on the correct odds. When DraftKings offers +150 on an outcome whose true probability is 42% (fair odds: +138), you're getting better value than you should. Each individual bet might win or lose, but across hundreds of +EV bets, the math guarantees a profit.
The challenge is determining "true probability." This is where sharp sportsbooks come in. Pinnacle's lines, with their 1-3% vig removed, serve as the market's best estimate of true probability. Any other sportsbook offering significantly different odds is either mispriced or slow to update — and that's your edge.
The EV Formula
EV% = (fair_probability × decimal_odds - 1) × 100
fair_probability — The true probability of the outcome, derived from a sharp line (e.g., Pinnacle) with vig removed. Expressed as a decimal (0.523, not 52.3%).
decimal_odds — The odds at the sportsbook you're evaluating, in decimal format. American -105 = 1.952 decimal. American +150 = 2.500 decimal.
Result interpretation — Positive = the bet has edge (you should bet it). Negative = the house has edge (you should skip it). Zero = break-even.
Vig Removal: Finding True Probability
Before you can calculate EV, you need the fair probability without the sportsbook's margin. Here's how to strip the vig from Pinnacle's line:
Pinnacle offers: Lakers -115 | Celtics +105
Step 1: Convert American odds to implied probability
Lakers: 115 / (115 + 100) = 0.535 (53.5%)
Celtics: 100 / (105 + 100) = 0.488 (48.8%)
Step 2: Sum the implied probabilities
Total = 0.535 + 0.488 = 1.023
The 2.3% above 100% is Pinnacle's vig
Step 3: Divide each by total to remove vig
Lakers fair: 0.535 / 1.023 = 0.523 (52.3%)
Celtics fair: 0.488 / 1.023 = 0.477 (47.7%)
Total = 100% ← vig is removedFull Worked Example
SCENARIO: Lakers vs Celtics
Pinnacle fair probability for Lakers: 52.3% (from vig removal above)
DraftKings offers Lakers at -105 (decimal: 1.952)
EV% = (fair_probability x decimal_odds - 1) x 100
EV% = (0.523 x 1.952 - 1) x 100
EV% = (1.021 - 1) x 100
EV% = +2.1%
INTERPRETATION: This Lakers bet at DraftKings has +2.1% EV.
Over 1,000 similar bets at $100 each, your expected profit
is approximately $2,100 (2.1% x $100,000 total wagered).EV Thresholds: How Much Edge Is Enough?
| EV Range | Quality | Notes |
|---|---|---|
| < 0% | Negative EV | House has the edge. Don't bet. |
| 0-2% | Marginal | Thin edge. Common on popular markets. High volume needed to see results. |
| 2-5% | Good | Solid value. This is the sweet spot for most +EV bettors. |
| 5-10% | Excellent | Strong edge, often from books slow to update. Act fast — these close quickly. |
| 10%+ | Rare | Possible line error. Book may void the bet. Bet cautiously. |
+EV Betting vs. Arbitrage
| Aspect | +EV Betting | Arbitrage |
|---|---|---|
| Risk per bet | You can lose individual bets | Guaranteed profit per event |
| Long-term edge | Higher expected returns | Lower but guaranteed returns |
| Capital needed | Moderate (bet one side) | High (bet both sides simultaneously) |
| Detection risk | Lower (looks like normal betting) | Higher (correlated bets across books) |
| Opportunity frequency | Many opportunities daily | Fewer, often brief windows |
| Variance | High (short-term swings) | Low (guaranteed per event) |
Most professional bettors combine both strategies: +EV for the bulk of their volume (higher returns, more sustainable) and arbitrage for guaranteed-profit situations when they appear.
Building a +EV Detection Tool
To detect +EV opportunities programmatically, you need two things: a sharp reference line (Pinnacle) and odds from the sportsbooks you want to compare against. SharpAPI provides both in a single API call.
Example: Find +EV Bets (TypeScript)
import SharpAPI from '@sharp-api/sdk'
const client = new SharpAPI({ apiKey: process.env.SHARPAPI_KEY })
// Get +EV opportunities across all sportsbooks
const ev = await client.ev.list({
sport: 'basketball_nba',
min_ev: 2.0, // Only show bets with 2%+ edge
})
for (const opportunity of ev.data) {
console.log(
`${opportunity.event}: ${opportunity.outcome}`,
`@ ${opportunity.bookmaker} ${opportunity.odds}`,
`EV: +${opportunity.ev_percent.toFixed(1)}%`,
`(Fair: ${opportunity.fair_odds})`
)
}SharpAPI computes EV server-side using Pinnacle fair lines, so you don't need to implement vig removal or EV calculation yourself. The +EV API returns pre-calculated opportunities, or you can stream them in real-time via SSE.