# Positive EV

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Canonical: https://novigapi.com/learn/positive-ev

A positive EV bet is one whose price pays more than its fair odds, so it is expected to make money on average over many repetitions.

```
EV per $1 = p_fair x decimal_odds - 1; positive when p_fair > 1 / decimal_odds
```

Positive EV, often written +EV, describes a bet with a positive expected value. It means the price you are offered implies a lower probability than the outcome's fair probability, so over many bets the winners pay more than the losers cost. Positive EV betting is the practice of finding those prices, usually by comparing a soft sportsbook to a sharp or exchange-derived fair price, and betting only when the gap is large enough.

## How it works

1. Find a fair probability for the outcome, usually by devigging a sharp market or reading an exchange midpoint.
2. Convert the price you are offered to decimal odds.
3. Multiply the fair probability by the decimal odds and subtract 1. A result above zero is positive EV.
4. Size the bet, often with a fraction of the Kelly criterion, and record the closing line to check your fair prices were right.

## Worked example

Suppose Novig's book shows a Yes bid of 55% and a No bid of 42%, so the fair price is 56.5% for Yes and 43.5% for No. Compare it with prices at a sportsbook:

EV against a Novig fair price

| Side | Fair probability | Book price | Decimal | EV per $1 |
| --- | --- | --- | --- | --- |
| Yes | 56.5% | -110 | 1.909 | +7.86% |
| Yes | 56.5% | +100 | 2.000 | +13.00% |
| No | 43.5% | +150 | 2.500 | +8.75% |
| Coin flip | 50.0% | +105 | 2.050 | +2.50% |
| Coin flip | 50.0% | -110 | 1.909 | -4.55% |


For Yes at -110: 0.565 x 1.90909 - 1 = 0.0786, or 7.86 cents per dollar. The last row shows why a standard -110 coin flip is negative EV. The [EV calculator](https://novigapi.com/ev-calculator) handles any price format.

## On Novig

Two things make Novig useful for EV work. Its fair midpoint is a no-vig benchmark built from traders' own orders, published per market by our `/fair-price` endpoint. And you can buy at the implied ask on Novig itself, so a Novig price can be the +EV bet, not just the reference. Remember the live taker fee of 0.06 x P x (1 - P) per contract when buying in-game: at 40% it costs $0.0144 per $1 of payout, which [Novig trading fees](https://docs.novig.com/api/concepts/fees) (checked 12 Nov 2026) waives on pregame game-market fills.

## Common mistakes

- Trusting a fair price from a stale or wide market. The EV is only as good as the benchmark.
- Ignoring limits. Soft books cut stakes on accounts that consistently find +EV prices.
- Expecting quick profit. A 3% edge loses often in the short run; CLV is the faster signal.

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