# Implied probability

## Free API key

Get a free GetOdds API key: **1,000 requests per UTC day and 60 per minute, no card**. One key covers REST and the hosted MCP server.

Sign up: https://getoddsapi.com/sign-up?ref=ai-claudebot

## Quickstart

1. Create an account at https://getoddsapi.com/sign-up?ref=ai-claudebot, open https://getoddsapi.com/dashboard and issue a key with the sources you need (draftkings, fanduel, betrivers, prizepicks or underdog). Keep it in a server environment variable named GETODDS_API_KEY.
2. Read current DraftKings NBA spreads with curl:

```bash
curl --fail-with-body "https://getoddsapi.com/api/v1/odds?sport=NBA&market=spread&fresh_only=true&limit=50" \
  -H "Authorization: Bearer $GETODDS_API_KEY"
```

3. The same request in Python (standard library only):

```python
import json, os, urllib.request

req = urllib.request.Request(
    "https://getoddsapi.com/api/v1/odds?sport=NBA&market=spread&fresh_only=true&limit=50",
    headers={"Authorization": "Bearer " + os.environ["GETODDS_API_KEY"]},
)
with urllib.request.urlopen(req) as res:
    rows = json.load(res)["data"]
for row in rows:
    print(row["away"], "at", row["home"], row["side"], row["line"], row["american"], row["observed_at"])
```

4. Check `observed_at`, `age_seconds` and `stale` on every row before using a price. Full reference: https://getoddsapi.com/docs

## Use with Claude (MCP)

```bash
claude mcp add --transport http getodds https://getoddsapi.com/api/mcp \
  --header "Authorization: Bearer $GETODDS_API_KEY"
```

The MCP tools follow the key's source grants and share its allowance. Setup guide: https://getoddsapi.com/use-with-claude

## Pricing

| Plan | Allowance | Price |
| --- | --- | --- |
| Free key | 1,000 requests a day, 60 a minute | $0, no card |
| Developer Bundle | 10,000 requests or credits a month on each of four sources | $149 a month |

Free development allowance: 1,000 requests per UTC day and 60 per minute per account, with no payment step. Paid: the Developer Bundle at $149 per month, with 10,000 monthly requests or credits on each of four sources.
Details: https://getoddsapi.com/bundle


Canonical page: https://getoddsapi.com/glossary/implied-probability

Implied probability is the break-even win rate represented by a quoted price in an all-or-nothing cash bet with no pushes or fees. It is found by dividing one by decimal odds. It is a threshold encoded in the price, not a measured forecast.

## Formula

Implied probability (%) = 100/d. Positive American a: d = 1 + a/100. Negative American a: d = 1 + 100/|a|.

## Why one divided by the price works

A decimal price includes the returned stake. At decimal odds d, a winning unit stake returns d units and a loss returns zero. If the win probability is p, expected net return per unit is p × d − 1. Setting that expression to zero gives p = 1/d.

That equation explains the threshold without estimating p. A market quote can reflect margin, demand and other pricing decisions; calling its reciprocal a “probability” does not turn it into a verified chance of winning. For mutually exclusive, exhaustive outcomes, the quoted implied probabilities may add up to more than 100%.

## Two common prices

1. +150 converts to 1 + 150/100 = 2.50; implied probability is 100/2.50 = 40%.
2. −110 converts to 1 + 100/110 = 1.9090909; implied probability is 52.380952%.
3. Two opposing −110 prices imply 104.761905% in total, rather than a coherent pair of probabilities summing to 100%.

## Assumptions and limits

This simple break-even model excludes pushes, partial payouts, stake-not-returned promotions, fees and taxes. For a complete market, removing margin requires an additional model; it does not reveal the true probabilities. Correlated selections also require a joint probability model, not blind multiplication of single-leg implied probabilities.

## Try the arithmetic

- [Convert a price to its break-even threshold](https://getoddsapi.com/implied-probability-calculator)
- [Compare odds formats](https://getoddsapi.com/odds-converter)

## Related terms

- [Vig](https://getoddsapi.com/glossary/vig)
- [No-vig odds](https://getoddsapi.com/glossary/no-vig)
- [Parlay](https://getoddsapi.com/glossary/parlay)

## Sources

- [Pinnacle: betting-margin terminology](https://support.pinnacle.com/hc/en-us/articles/44854177573009-What-is-a-betting-margin)

Examples are illustrative, not live offers or betting recommendations.

## FAQ

### Is there a free odds API key?

Yes. A free GetOdds key includes 1,000 requests per UTC day and 60 per minute, with no card.

### Which sportsbooks does the API cover?

DraftKings (prices observed through ESPN), FanDuel (native game markets and futures) and BetRivers (Pennsylvania pregame markets), plus PrizePicks, Underdog and Pick6 lines.

### Does it work with Claude?

Yes. Add the hosted MCP server with `claude mcp add --transport http getodds https://getoddsapi.com/api/mcp` and your key in the Authorization header.

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GetOdds is an independent developer product and is not affiliated with any sportsbook or pick’em operator. Prices describe data, not betting advice.