{
  "id": "dpo",
  "version": "047d24c3586b",
  "status": "published",
  "name": "Days Past Ovulation (DPO) Calculator",
  "question": "How many DPO am I today?",
  "summary": "Counts the days past ovulation (DPO) on a chosen day, from the ovulation day or the last period and cycle length, and says what usually happens at that DPO: implantation, the period due date, and when a test is reliable.",
  "category": "health",
  "subcategory": "pregnancy",
  "url": "https://www.acalculator.org/health/dpo-calculator",
  "markdown": "https://www.acalculator.org/health/dpo-calculator.md",
  "kind": "function",
  "method": "DPO = chosen day − ovulation day; ovulation = last period + cycle length − 14 days (or the day entered); period due = ovulation + 14 days.",
  "assumptions": [
    "Ovulation comes 14 days before the next period (ACOG average); real cycles vary.",
    "Implantation happened 6 to 12 days after ovulation, most often on day 8, 9 or 10 (Wilcox and others, 1999).",
    "Most home pregnancy tests are reliable from the first day of a missed period (womenshealth.gov)."
  ],
  "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 a temperature chart.",
        "type": "string",
        "format": "date"
      },
      "on": {
        "title": "DPO on",
        "description": "The day to count to; today by default.",
        "type": "string",
        "format": "date"
      }
    }
  },
  "outputs": {
    "dpo": {
      "label": "Days past ovulation",
      "description": "Days from ovulation to the chosen day.",
      "format": "integer"
    },
    "stage": {
      "label": "What usually happens",
      "description": "The usual events at this DPO.",
      "format": "text"
    },
    "ovulation": {
      "label": "Ovulation",
      "description": "The ovulation day: entered, or the last period + cycle length − 14 days.",
      "format": "date"
    },
    "period": {
      "label": "Next period due",
      "description": "Ovulation + 14 days.",
      "format": "date"
    },
    "toPeriod": {
      "label": "Days until the period is due",
      "description": "14 − DPO; 0 or less means the period is due or late.",
      "format": "integer"
    },
    "implantFrom": {
      "label": "Implantation window from",
      "description": "Ovulation + 6 days.",
      "format": "date"
    },
    "implantTo": {
      "label": "Implantation window to",
      "description": "Ovulation + 12 days.",
      "format": "date"
    }
  },
  "defaultAnswer": {
    "inputs": {
      "from": "period",
      "lmp": "2026-09-14",
      "cycle": 28,
      "ovulation": "2026-09-28",
      "on": "2026-10-05"
    },
    "outputs": {
      "dpo": 7,
      "stage": "In the implantation window (6 to 12 DPO)",
      "ovulation": "2026-09-28",
      "period": "2026-10-12",
      "toPeriod": 7,
      "implantFrom": "2026-10-04",
      "implantTo": "2026-10-10"
    },
    "text": "On October 5, 2026 you are 7 days past ovulation (DPO)."
  },
  "examples": [
    {
      "given": {
        "from": "period",
        "lmp": "2026-09-01",
        "cycle": 28,
        "on": "2026-09-24"
      },
      "expect": {
        "ovulation": "2026-09-15",
        "dpo": 9,
        "stage": "In the most likely implantation days (8 to 10 DPO)",
        "period": "2026-09-29",
        "toPeriod": 5,
        "implantFrom": "2026-09-21",
        "implantTo": "2026-09-27"
      },
      "source": "ACOG Committee Opinion 700, Methods for Estimating the Due Date (ovulation about 14 days before the next period), https://www.acog.org/clinical/clinical-guidance/committee-opinion/articles/2017/05/methods-for-estimating-the-due-date; Wilcox AJ, Baird DD, Weinberg CR, Time of implantation of the conceptus and loss of pregnancy, N Engl J Med 1999;340:1796 (implantation 6 to 12 days after ovulation, 84% on day 8, 9 or 10), https://doi.org/10.1056/NEJM199906103402304; hand calculation in content.mdx: ovulation Sep 1 + 14 = Sep 15; Sep 24 − Sep 15 = 9 DPO"
    },
    {
      "given": {
        "from": "ovulation",
        "ovulation": "2026-12-25",
        "on": "2027-01-08"
      },
      "expect": {
        "dpo": 14,
        "period": "2027-01-08",
        "toPeriod": 0,
        "stage": "Period due today: a home pregnancy test is reliable from a missed period"
      },
      "source": "ACOG Committee Opinion 700, Methods for Estimating the Due Date (ovulation about 14 days before the next period), https://www.acog.org/clinical/clinical-guidance/committee-opinion/articles/2017/05/methods-for-estimating-the-due-date; hand calculation in content.mdx: Dec 25 to Jan 8 is 14 days"
    },
    {
      "given": {
        "from": "period",
        "lmp": "2028-02-10",
        "cycle": 32,
        "on": "2028-03-03"
      },
      "expect": {
        "ovulation": "2028-02-28",
        "dpo": 4,
        "period": "2028-03-13"
      },
      "source": "ACOG Committee Opinion 700, Methods for Estimating the Due Date (ovulation about 14 days before the next period), https://www.acog.org/clinical/clinical-guidance/committee-opinion/articles/2017/05/methods-for-estimating-the-due-date; hand calculation in content.mdx: Feb 10 + 18 = Feb 28; Feb 28 to Mar 3 in 2028 (Feb 29 exists) is 4 days"
    }
  ],
  "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",
    "Office on Women’s Health (HHS). Pregnancy tests: most home tests are accurate after a missed period, retrieved 2026-10-05. https://womenshealth.gov/a-z-topics/pregnancy-tests"
  ],
  "related": [
    "implantation",
    "pregnancy-test",
    "ovulation"
  ],
  "changelog": []
}