Ovulation & fertile window API

Estimate the ovulation date, fertile window, and next period from the last menstrual period and cycle length via the calendar method (ovulation = cycleLength − lutealPhase). Answers 'when do I ovulate', 'fertile window from my last period', 'ovulation calculator', 'most fertile days'.

Price$0.01per request

MethodPOST

Route/v1/health/ovulation

StatusLive

MIME typeapplication/json

Rate limit120/minute

CacheNo cache

healthovulationfertilitymenstrualcyclefertile-windowreproductivecalculator

API URLhttps://x402.hexl.dev/v1/health/ovulation

Integration docs

Example request

{
  "lmpDate": "2025-01-01",
  "cycleLength": 28
}

Example response

{
  "ovulationDate": "2025-01-15",
  "method": "Calendar method (ovulation = cycleLength - lutealPhase)",
  "fertileWindow": {
    "start": "2025-01-10",
    "end": "2025-01-16"
  },
  "nextPeriodDate": "2025-01-29",
  "ovulationDayOfCycle": 14,
  "inputs": {
    "lmpDate": "2025-01-01",
    "cycleLength": 28,
    "lutealPhase": 14
  }
}

Input schema

{
  "type": "object",
  "required": [
    "lmpDate"
  ],
  "properties": {
    "lmpDate": {
      "type": "string",
      "description": "First day of last menstrual period (ISO date)",
      "examples": [
        "2025-01-01"
      ]
    },
    "cycleLength": {
      "type": "number",
      "default": 28,
      "description": "21-45 days",
      "examples": [
        28
      ]
    },
    "lutealPhase": {
      "type": "number",
      "default": 14,
      "examples": [
        14
      ]
    }
  }
}

Output schema

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