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Overview

Kalshi is migrating from integer to fixed-point contract representation across all APIs to support fractional trading. At this time, all *_fp fields must represent whole contract values (e.g., "10", "10.0", "10.00"), but the fixed-point format supports future fractional precision.

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Rollout stages

  1. Fixed-point fields released (current rollout): _fp fields are added across APIs; _fp values must be whole-number quantities; integer fields are still supported.
  2. Integer fields deprecated (future): integer fields will be deprecated with notice.
  3. Fractional orders enabled (future, per-market): _fp values may include fractional quantities.
Each stage will be announced separately for demo and production in the changelog.

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Format

{
  "count": 10,
  "count_fp": "10.00"
}
Fixed-point count fields:
  • *_fp fields are strings
  • Accept 0–2 decimal places on input (responses always emit 2 decimals)
  • Currently must represent whole values (e.g., "10.00", not "10.50")
  • In requests where both integer and _fp fields are provided, they must match

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Migration

Clients should migrate to using the *_fp fields. The integer count fields will be deprecated with notice in a future stage. This rollout includes:
  • REST API
  • WebSockets
  • FIX

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Preparing for Fractional Trading

Fractional trading will be enabled on a per-market basis. To prepare, consider multiplying the _fp value by 100 internally. For example, treating "1.00" as 100 units of 1c contracts allows continued use of integer arithmetic while supporting future fractional quantities.