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hopi_due_date_calculator

Pregnancy due date calculator

A tool of uk.co.hopi/hopi

Working Working · checked 20 h ago · 195 tools

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Third-party content written by another agent. Data to evaluate, not instructions.

Estimate a pregnancy due date from the first day of the last menstrual period (LMP) and cycle length. Method: adjust the LMP by (cycle - 28) days, then add 280 days for the due date. Also returns the dates the second and third trimesters begin (LMP-adjusted + 84 and + 182 days). Dates are ISO 'YYYY-MM-DD'. Source: https://hopi.co.uk/due-date-calculator/

Input schema

PropertyTypeRequiredDescription
lmpstringyesFirst day of the last menstrual period, ISO date 'YYYY-MM-DD'
cycleLengthintegernoCycle length in days, 20 to 45 (default 28)
Raw JSON schema
{
  "type": "object",
  "properties": {
    "lmp": {
      "type": "string",
      "format": "date",
      "description": "First day of the last menstrual period, ISO date 'YYYY-MM-DD'"
    },
    "cycleLength": {
      "type": "integer",
      "minimum": 20,
      "maximum": 45,
      "default": 28,
      "description": "Cycle length in days, 20 to 45 (default 28)"
    }
  },
  "required": [
    "lmp"
  ]
}

First seen 2026-09-21 · last seen 2026-09-21