{
    "name": "Pregnancy Weight Gain Calculator",
    "url": "https://calculators.geekmidst.com/calculators/pregnancy-weight-gain-calculator",
    "markdown": "https://calculators.geekmidst.com/calculators/pregnancy-weight-gain-calculator.md",
    "category": "Health & fitness",
    "description": "See the recommended total pregnancy weight gain for your pre-pregnancy BMI under the IOM 2009 guidelines, and the typical range for your current week.",
    "summary": "How much weight to gain in pregnancy depends on your BMI before pregnancy. The Institute of Medicine (IOM, 2009) guidelines give a total range and a weekly rate for the second and third trimesters.",
    "also_called": [
        "Gestational weight gain calculator"
    ],
    "applies_to": "Worldwide",
    "last_updated": "2026-10-29",
    "computation": "Results are computed in the visitor’s browser on the HTML page. This API describes the calculator; it does not compute results.",
    "inputs": [
        {
            "name": "units",
            "label": "Units",
            "type": "segmented",
            "default": "metric",
            "options": {
                "metric": "Metric (cm, kg)",
                "us": "US (ft, in, lb)"
            }
        },
        {
            "name": "height_cm",
            "label": "Height",
            "type": "number",
            "default": "165",
            "unit": "cm",
            "shown_when": {
                "units": "metric"
            }
        },
        {
            "name": "pre_kg",
            "label": "Weight before pregnancy",
            "type": "number",
            "default": "60",
            "unit": "kg",
            "shown_when": {
                "units": "metric"
            }
        },
        {
            "name": "current_kg",
            "label": "Current weight",
            "type": "number",
            "default": "66",
            "unit": "kg",
            "shown_when": {
                "units": "metric"
            }
        },
        {
            "name": "height_ft",
            "label": "Height (feet)",
            "type": "number",
            "default": "5",
            "unit": "ft",
            "shown_when": {
                "units": "us"
            }
        },
        {
            "name": "height_in",
            "label": "Height (inches)",
            "type": "number",
            "default": "5",
            "unit": "in",
            "optional": true,
            "shown_when": {
                "units": "us"
            }
        },
        {
            "name": "pre_lb",
            "label": "Weight before pregnancy",
            "type": "number",
            "default": "132",
            "unit": "lb",
            "shown_when": {
                "units": "us"
            }
        },
        {
            "name": "current_lb",
            "label": "Current weight",
            "type": "number",
            "default": "145",
            "unit": "lb",
            "shown_when": {
                "units": "us"
            }
        },
        {
            "name": "week",
            "label": "Week of pregnancy",
            "type": "number",
            "default": "24",
            "unit": "weeks"
        },
        {
            "name": "twins",
            "label": "Pregnancy",
            "type": "segmented",
            "default": "single",
            "options": {
                "single": "One baby",
                "twins": "Twins"
            }
        }
    ],
    "outputs": [
        {
            "key": "total_range",
            "label": "Recommended total gain",
            "format": "text"
        },
        {
            "key": "bmi",
            "label": "Pre-pregnancy BMI",
            "format": "number"
        },
        {
            "key": "category",
            "label": "BMI category",
            "format": "text"
        },
        {
            "key": "gained",
            "label": "Gained so far (kg or lb)",
            "format": "number"
        },
        {
            "key": "range_now",
            "label": "Typical gain by this week",
            "format": "text"
        },
        {
            "key": "status",
            "label": "Compared with the typical range",
            "format": "text"
        }
    ],
    "formula": {
        "text": "BMI = pre-pregnancy kg ÷ m²;  by week w ≤ 13: first-trimester gain × w ÷ 13;  after 13 weeks: first-trimester gain + weekly rate × (w − 13)",
        "variables": {
            "first-trimester gain": "0.5–2 kg (1.1–4.4 lb)",
            "weekly rate": "IOM range for your BMI group, e.g. 0.35–0.50 kg a week for normal weight"
        }
    },
    "worked_example": {
        "inputs": {
            "units": "metric",
            "height_cm": "165",
            "pre_kg": "60",
            "current_kg": "66",
            "height_ft": "5",
            "height_in": "5",
            "pre_lb": "132",
            "current_lb": "145",
            "week": "24",
            "twins": "single"
        },
        "steps": [
            "Pre-pregnancy BMI = 60 ÷ 1.65² = 22.0: normal weight, so the IOM total is 11.5–16 kg.",
            "By week 24 (11 weeks after week 13): 0.5 + 0.35 × 11 = 4.4 kg to 2 + 0.50 × 11 = 7.5 kg.",
            "Gained so far: 66 − 60 = 6 kg, which is within that range."
        ],
        "result": "With a pre-pregnancy BMI of 22.0 the recommended total gain is 11.5–16 kg; 6 kg at 24 weeks is within the typical range."
    },
    "interpretation": "The total range is the IOM recommendation. The week-by-week figure is a guide built from the IOM’s assumed first-trimester gain and weekly rates, so small differences from it are not a concern. Your midwife or doctor will interpret your gain alongside your baby’s growth and your health.",
    "assumptions": [
        "IOM (2009) totals: underweight 12.5–18 kg (28–40 lb), normal 11.5–16 kg (25–35 lb), overweight 7–11.5 kg (15–25 lb), obese 5–9 kg (11–20 lb).",
        "Second- and third-trimester weekly ranges: 0.44–0.58, 0.35–0.50, 0.23–0.33 and 0.17–0.27 kg (1.0–1.3, 0.8–1.0, 0.5–0.7, 0.4–0.6 lb).",
        "Provisional twin totals: normal 16.8–24.5 kg (37–54 lb), overweight 14.1–22.7 kg (31–50 lb), obese 11.5–19.1 kg (25–42 lb)."
    ],
    "limitations": [
        "No IOM twin guideline exists for a pre-pregnancy BMI under 18.5, and no week-by-week twin ranges are given.",
        "Not for pregnancies with three or more babies.",
        "Does not replace advice from your maternity care team."
    ],
    "rules": null,
    "faqs": [
        {
            "question": "Why is less gain recommended with a higher BMI?",
            "answer": "The guidelines balance risks to mother and baby; with more stored energy before pregnancy, a smaller gain is associated with better outcomes."
        },
        {
            "question": "I am losing weight in the first trimester because of sickness. Is that a problem?",
            "answer": "Small losses with nausea are common early on, but tell your midwife or doctor, especially if you cannot keep fluids down."
        }
    ],
    "sources": [
        {
            "title": "IOM 2009 recommendations table, reproduced in Ann Epidemiol 2014 (PMC4029921)",
            "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC4029921/table/T1"
        },
        {
            "title": "Merck Manual Professional: Guidelines for weight gain during pregnancy",
            "url": "https://www.merckmanuals.com/professional/multimedia/table/guidelines-for-weight-gain-during-pregnancy"
        }
    ],
    "related": [
        {
            "name": "Pregnancy Calculator",
            "url": "https://calculators.geekmidst.com/calculators/pregnancy-calculator"
        },
        {
            "name": "Due Date Calculator",
            "url": "https://calculators.geekmidst.com/calculators/due-date-calculator"
        },
        {
            "name": "BMI Calculator",
            "url": "https://calculators.geekmidst.com/calculators/bmi-calculator"
        },
        {
            "name": "Healthy Weight Calculator",
            "url": "https://calculators.geekmidst.com/calculators/healthy-weight-calculator"
        }
    ],
    "disclaimer": "This is a general screening estimate for adults, not medical advice or a diagnosis. Talk to a qualified health professional about your health.",
    "publisher": "GM¹X CalcVerse"
}