{
  "id": "implantation",
  "version": "4231ec713617",
  "status": "published",
  "name": "Implantation Calculator",
  "question": "When will implantation happen?",
  "summary": "Estimates when implantation happens: 6 to 12 days after ovulation, most often 8 to 10, from the last period and cycle length or the ovulation date.",
  "category": "health",
  "subcategory": "pregnancy",
  "url": "https://www.acalculator.org/health/implantation-calculator",
  "markdown": "https://www.acalculator.org/health/implantation-calculator.md",
  "kind": "function",
  "method": "Ovulation = last period + cycle length − 14 days (or the day entered); implantation 6 to 12 days after ovulation, most likely 8 to 10 days after.",
  "assumptions": [
    "Ovulation comes 14 days before the next period (ACOG average); real cycles vary.",
    "Implantation, seen as the first rise of hCG, happened 6 to 12 days after ovulation in pregnancies that lasted, and on day 8, 9 or 10 in 84% of them (Wilcox and others, 1999).",
    "These are estimates, not medical advice; spotting has many causes."
  ],
  "inputs": {
    "$schema": "https://json-schema.org/draft/2020-12/schema",
    "type": "object",
    "properties": {
      "from": {
        "title": "What do you know?",
        "description": "The first day of your last period, or the day you ovulated.",
        "type": "string",
        "enum": [
          "period",
          "ovulation"
        ]
      },
      "lmp": {
        "title": "First day of your last period",
        "description": "The first day of bleeding of your most recent period.",
        "type": "string",
        "format": "date"
      },
      "cycle": {
        "title": "Cycle length (days)",
        "description": "Days from the first day of one period to the first day of the next; 28 on average.",
        "type": "integer",
        "minimum": 20,
        "maximum": 45
      },
      "ovulation": {
        "title": "Ovulation day",
        "description": "The day you ovulated, for example from an ovulation test or temperature chart.",
        "type": "string",
        "format": "date"
      }
    }
  },
  "outputs": {
    "likely": {
      "label": "Most likely implantation",
      "description": "The days implantation happens most often: 8 to 10 days after ovulation.",
      "format": "text"
    },
    "likelyFrom": {
      "label": "Most likely from",
      "description": "The first of the most likely days: 8 days after ovulation.",
      "format": "date"
    },
    "likelyTo": {
      "label": "Most likely to",
      "description": "The last of the most likely days: 10 days after ovulation.",
      "format": "date"
    },
    "from": {
      "label": "Possible from",
      "description": "The earliest usual implantation day: 6 days after ovulation.",
      "format": "date"
    },
    "to": {
      "label": "Possible up to",
      "description": "The latest usual implantation day: 12 days after ovulation.",
      "format": "date"
    },
    "ovulation": {
      "label": "Ovulation",
      "description": "The ovulation day: entered, or the last period + cycle length − 14 days.",
      "format": "date"
    },
    "period": {
      "label": "Next period due",
      "description": "The day the next period should start: 14 days after ovulation.",
      "format": "date"
    }
  },
  "defaultAnswer": {
    "inputs": {
      "from": "period",
      "lmp": "2026-09-09",
      "cycle": 28,
      "ovulation": "2026-09-23"
    },
    "outputs": {
      "likely": "October 1, 2026 to October 3, 2026",
      "likelyFrom": "2026-10-01",
      "likelyTo": "2026-10-03",
      "from": "2026-09-29",
      "to": "2026-10-05",
      "ovulation": "2026-09-23",
      "period": "2026-10-07"
    },
    "text": "Implantation most likely happens between October 1, 2026 and October 3, 2026."
  },
  "examples": [
    {
      "given": {
        "from": "period",
        "lmp": "2026-09-01",
        "cycle": 28
      },
      "expect": {
        "ovulation": "2026-09-15",
        "likelyFrom": "2026-09-23",
        "likelyTo": "2026-09-25",
        "likely": "September 23, 2026 to September 25, 2026",
        "from": "2026-09-21",
        "to": "2026-09-27",
        "period": "2026-09-29"
      },
      "source": "ACOG (ovulation 14 days before the next period); Wilcox 1999 (implantation 6 to 12 days after ovulation, 84% on days 8 to 10); hand calculation in content.mdx"
    },
    {
      "given": {
        "from": "period",
        "lmp": "2026-10-01",
        "cycle": 32
      },
      "expect": {
        "ovulation": "2026-10-19",
        "likelyFrom": "2026-10-27",
        "likelyTo": "2026-10-29",
        "period": "2026-11-02"
      },
      "source": "A 32-day cycle: ovulation on day 18; Wilcox 1999; hand calculation in content.mdx"
    },
    {
      "given": {
        "from": "ovulation",
        "ovulation": "2026-12-28"
      },
      "expect": {
        "from": "2027-01-03",
        "likelyFrom": "2027-01-05",
        "likelyTo": "2027-01-07",
        "to": "2027-01-09"
      },
      "source": "Wilcox 1999 (6 to 12 days after ovulation, most often 8 to 10); hand calculation in content.mdx"
    }
  ],
  "sources": [
    "Wilcox AJ, Baird DD, Weinberg CR. Time of implantation of the conceptus and loss of pregnancy. N Engl J Med. 1999;340(23):1796-1799. https://doi.org/10.1056/NEJM199906103402304",
    "American College of Obstetricians and Gynecologists. Committee Opinion No. 700: Methods for Estimating the Due Date (ovulation about 14 days before the next period). Obstet Gynecol. 2017;129(5):e150-e154. https://www.acog.org/clinical/clinical-guidance/committee-opinion/articles/2017/05/methods-for-estimating-the-due-date"
  ],
  "related": [
    "pregnancy-test",
    "ovulation",
    "pregnancy-week"
  ],
  "changelog": []
}