# Betting EV calculator (expected value)

> Independent. Not affiliated with, endorsed by or sponsored by Novig.

Canonical: https://novigapi.com/ev-calculator
Method checked: 2026-11-12
Interactive tool: https://novigapi.com/ev-calculator (prefill with ?a=&b=)

Expected value per $1 is p x (decimal - 1) - (1 - p). A bet at +100 that is fair at 52% has EV of +4.00%, so $100 is worth $4.00 on average. Fair probabilities often come from an exchange: the Novig two-sided mid has no vig (Novig docs, checked 12 Nov 2026).

## Worked example

Worked examples, $100 stake

| Fair probability | Price | EV per $1 | EV on $100 |
| --- | --- | --- | --- |
| 52% | +100 | 4.00% | $4.00 |
| 50% | -110 | -4.55% | -$4.55 |
| 40% | +160 | 4.00% | $4.00 |
| 60% | -130 | 6.15% | $6.15 |

```
EV = p x (D - 1) - (1 - p)
edge = p - 1/D
```

The result is only as good as the fair probability. The usual sources are a devigged sharp market or an exchange mid. In the first example, EV of 4.00% per $1 means a $100 bet earns $4.00 on average over many repeats; a single bet still wins or loses the full amount.

Positive EV is a long-run property. Size bets with a fraction of Kelly to keep the swings survivable, and track closing-line value to check that your fair probabilities are any good.

## How to use it

1. Enter your fair probability (or a no-vig price).
2. Enter the price offered.
3. Read EV in dollars and percent, and the edge over the break-even probability.

## Questions

### What is a good EV in betting?

Any positive EV is profitable in the long run; most +EV bets found by devigging are in the 1-5% range.

### Where does the fair probability come from?

Usually from devigging a sharp market or reading an exchange mid such as Novig's, which has no vig.

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