> ## Documentation Index
> Fetch the complete documentation index at: https://docs.therundown.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Choose an odds format

> Request American, decimal, fractional, or probability odds from REST endpoints while keeping the default response unchanged.

Use the optional `odds_format` query parameter on V1 and V2 REST `GET` endpoints to choose how sportsbook prices are returned. It also applies to `GET /api/v2/public/odds/{sportID}` and RapidAPI REST mirrors. The public snapshot contents and delay remain unchanged. WebSocket messages remain unchanged.

If you omit `odds_format` or set it to `american`, the response stays byte-for-byte unchanged in its existing American format. Set the value once, in lowercase:

| Value | Example for an American price of `-110` | Example for `+150` | Output type |
| - | - | - | - |
| `american` | `-110` | `150` | Existing response type; default |
| `decimal` | `1.909091` | `2.5` | Preserves whether the source field is a number or numeric string |
| `fractional` | `10/11` | `3/2` | Reduced ratio string |
| `probability` | `0.52381` | `0.4` | Implied, not de-vigged, probability from 0 to 1; preserves whether the source field is a number or numeric string |

Decimal and probability values are rounded to six decimal places with trailing zeroes removed. For extreme valid prices, probability output uses additional precision when needed so the value does not round to `0` or `1`. Fractional output is reduced to its exact ratio.

## Request a format

```bash cURL theme={null}
if [ -z "${API_KEY:-}" ]; then
  echo "Set API_KEY" >&2
  exit 1
fi

curl --fail-with-body --compressed \
  -H "X-TheRundown-Key: ${API_KEY}" \
  "https://therundown.io/api/v2/sports/4/events/2026-11-13?market_ids=1,2,3&odds_format=decimal"
```

The parameter works the same way on V1 responses:

```bash cURL theme={null}
curl --fail-with-body --compressed \
  -H "X-TheRundown-Key: ${API_KEY}" \
  "https://therundown.io/api/v1/events/EVENT_ID?odds_format=fractional"
```

A successful non-American JSON response includes the `X-Odds-Format` response header with the selected format.

## What changes

The API converts supported price fields, including `price`, `fair_price`, `adjusted_price`, `previous_price`, V1 moneyline/spread/total prices, hedge prices, promotion prices, and compact chart-history prices. A numeric source value stays numeric for decimal and probability output; a numeric string stays a string. Fractional prices are strings in either case.

The API leaves line values, IDs, probabilities already present in the response, liquidity values, and other non-price fields unchanged. Explicit unit fields such as `american_odds` and `decimal_odds` are unchanged. Delta fields such as `price_delta` and `*_money_delta` remain in American-point difference units; they are not recalculated into another odds format.

Values that are not convertible American prices stay unchanged. This includes `null`, nonnumeric sentinels, off-board placeholders such as `0` and `0.0001`, and numeric values whose absolute value is below `100`.

Empty, repeated, or unsupported `odds_format` values return HTTP `400`. Supported values are `american`, `decimal`, `fractional`, and `probability`. The selected representation changes only returned odds; it does not change the requested markets, lines, event scope, or snapshot delay.


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