Pregnancy Due Date Calculator
Calculate your estimated due date and track key pregnancy milestones.
About this tool
Pregnancy is one of life's most significant journeys, and knowing your estimated due date is a crucial first step. This calculator uses Naegele's rule, the gold standard method in obstetrics, to estimate your delivery date based on the first day of your last menstrual period. The calculation adds 280 days (40 weeks) to this date, giving you a reliable benchmark for planning and monitoring. Understanding your due date helps you prepare emotionally and practically for your baby's arrival.
Using this tool is simple: enter the first day of your last menstrual period into the date field and click calculate. The tool immediately displays your estimated due date, current gestational age in weeks and days, which trimester you are in, and key pregnancy milestones such as the first ultrasound window, anatomy scan, and viability thresholds. These milestones are helpful reference points as you navigate prenatal appointments and plan ahead.
While this calculator provides a good starting estimate, remember that only about 5% of babies are born on their exact due date. Normal delivery occurs anywhere between 37 and 42 weeks, so your due date is best understood as a statistical midpoint rather than a precise prediction. If your menstrual cycles are irregular or longer than 28 days, your actual due date may differ β a first-trimester ultrasound is the most accurate way to confirm. Always consult your healthcare provider for personalized guidance, as they can adjust dates based on your individual circumstances and monitor your pregnancy safely.
Frequently Asked Questions
Code Implementation
from datetime import date, timedelta
def calculate_due_date(lmp: date) -> dict:
"""Calculate estimated due date using Naegele's rule (LMP + 280 days)."""
due_date = lmp + timedelta(days=280)
today = date.today()
days_remaining = (due_date - today).days
gestational_days = (today - lmp).days
gestational_weeks = gestational_days // 7
gestational_day_rem = gestational_days % 7
return {
"lmp": lmp.strftime("%Y-%m-%d"),
"due_date": due_date.strftime("%Y-%m-%d"),
"days_remaining": days_remaining,
"gestational_age": f"{gestational_weeks}w {gestational_day_rem}d",
}
# Example
lmp = date(2025, 1, 15)
result = calculate_due_date(lmp)
print(f"Last Menstrual Period : {result['lmp']}")
print(f"Estimated Due Date : {result['due_date']}")
print(f"Days Remaining : {result['days_remaining']}")
print(f"Gestational Age : {result['gestational_age']}")Comments & Feedback
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