Tidal height API

Estimates tidal height at an intermediate time between low and high water using the rule of twelfths, with elapsed twelfths and fraction of range. Answers 'What is the tide height 3 hours after low water?', 'How much of the tidal range has come in by now?'.

Price$0.04per request

MethodPOST

Route/v1/nav/rule-of-twelfths

StatusLive

MIME typeapplication/json

Rate limit120/minute

Cache0s public

marinetidetidal-heightrule-of-twelfthssailingdepthclearancenavigation

API URLhttps://x402.hexl.dev/v1/nav/rule-of-twelfths

Integration docs

Example request

{
  "lowWaterHeightM": 1,
  "highWaterHeightM": 5,
  "hoursAfterStart": 3,
  "risingTide": true
}

Example response

{
  "tidalHeightM": 3,
  "fractionOfRange": 0.5,
  "twelfthsElapsed": 6,
  "rangeM": 4,
  "direction": "rising (flood)",
  "interpretation": "Tide height 3 m at 3 h after low water (50% of the 4 m range)."
}

Input schema

{
  "type": "object",
  "required": [
    "lowWaterHeightM",
    "highWaterHeightM",
    "hoursAfterStart"
  ],
  "properties": {
    "lowWaterHeightM": {
      "type": "number",
      "examples": [
        1
      ]
    },
    "highWaterHeightM": {
      "type": "number",
      "examples": [
        5
      ]
    },
    "tidePeriodHours": {
      "type": "number",
      "examples": [
        6
      ]
    },
    "hoursAfterStart": {
      "type": "number",
      "examples": [
        3
      ]
    },
    "risingTide": {
      "type": "boolean",
      "examples": [
        true
      ]
    }
  }
}

Output schema

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