Climb gradient & rate API

Converts between climb rate (fpm), gradient percent and ft-per-nm at a ground speed, returning climb angle. Answers 'What gradient is 500 fpm at 120 kt?', 'What climb rate do I need for a 250 ft/nm gradient?'.

Price$0.04per request

MethodPOST

Route/v1/nav/climb-gradient

StatusLive

MIME typeapplication/json

Rate limit120/minute

Cache0s public

aviationclimb-gradientfpmft-per-nmclimb-ratedepartureobstacleperformance

API URLhttps://x402.hexl.dev/v1/nav/climb-gradient

Integration docs

Example request

{
  "groundSpeedKt": 120,
  "climbRateFpm": 500
}

Example response

{
  "gradientPercent": 4.11,
  "gradientFtPerNm": 250,
  "climbAngleDeg": 2.36,
  "climbRateFpm": 500,
  "groundSpeedKt": 120,
  "interpretation": "4.11% gradient = 250 ft/nm = 500 fpm at 120 kt GS (2.36 deg)."
}

Input schema

{
  "type": "object",
  "required": [
    "groundSpeedKt"
  ],
  "properties": {
    "groundSpeedKt": {
      "type": "number",
      "examples": [
        120
      ]
    },
    "climbRateFpm": {
      "type": "number",
      "examples": [
        500
      ]
    },
    "gradientPercent": {
      "type": "number"
    },
    "gradientFtPerNm": {
      "type": "number"
    }
  }
}

Output schema

{
  "type": "object",
  "additionalProperties": true
}