> For the complete documentation index, see [llms.txt](https://docs.lsports.eu/u/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.lsports.eu/u/trade/concepts/probability.md).

# Probability

### **What is Probability?**

Probability, in the context of betting, represents the likelihood of a specific outcome occurring. TRADE calculates probability based on the current market odds and margin.

### **How is Probability Calculated?**

Probability is derived using the following formula:

**Probability = 1 / (current margin \* odd) = 1 / fair odd**

* **Current margin:** The margin applied to the odds by TRADE.
* **Odd:** The current odds for the specific outcome.
* **Fair odd:** The theoretical odds without any margin applied.

### **Receiving Probability Information:**

Probability is communicated to you as part of market update messages. It is displayed next to the Price (Odd) field within the Bet object for both InPlay and PreMatch events.

When the probability field value is "-1", customers should not calculate the cash-out amount for bets under this market or line.

### **Handling Bet Price Changes**

Delta updates are triggered by price changes, not probability changes. When a raw price changes, TRADE recalculates the fair price of every outcome in the market, including outcomes whose raw price did not change. Sibling outcomes may not be included in that delta — for example, if minimum-diff thresholds or rounding rules are configured and the sibling's price did not cross them.

This means operators who consume the `Probability` field without using `Price` may hold a locally inconsistent probability distribution between full snapshots.

{% hint style="info" %}
If your integration relies on `Probability` values and `Price`, you can request probability-delta updates for your packages — these ensure all affected outcomes are included in every delta, even when only their probability changed. Contact your CSM to enable this.
{% endhint %}

When probability delta updates are on, and there is a change in the probability of a bet due to a change in the price of another bet, even when the original bet price remains unchanged, a market update message is sent to the customer. For instance, in a 1x2 market:

* If the price of bet “1” changes, affecting the probability of all bets, a market update message is sent with all bet updates:
  * Bet “1” with price and probability update
  * Bets “2” and “x” with probability updates

This approach ensures that you are always updated with the latest data.

### **Cases Where Probability Is Sent as -1**

* **Provider Suspensions:** When a provider suspends a bet, TRADE cannot clean the margin for that provider if not all bets are provided by them. In such cases, the average margin from providers for the whole market (or line) is used, and the true odds are not sent.
* **Outright League Markets:** Probability is not supported.
* **Correct Score/Number of Goals Markets:** The probability is sent only for **tennis** and **table tennis** in these markets.
* **"Provider's margin Only" Markets:** Probability is not supported.
* **Suspended or Lower Odds:** If one of the market bets is equal to or lower than 1.00.

### **Probability Sum and Rounding**

Probabilities are calculated per outcome independently and are not normalized to sum to exactly 1. Each value is rounded to 5 decimal places, which introduces a small drift across a market — typically ±0.002 for a 3-way market. This is expected behavior. Operators who require a normalized distribution must normalize on their side after receiving the values.


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