Pregnancy Due Date Calculator
Calculate your estimated due date, gestational week and trimester from LMP
tuneLMP Details
Naegele's Rule
Due Date = LMP + 280 days (40 weeks)
Adjusted for non-28 day cycles: add or subtract the difference from 28 days.
Conception ≈ LMP + 14 days (ovulation)
Gestational Age = Days from LMP to today
Estimated Due Date
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—
Current Week
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Gestational Week
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Trimester
—
Days Remaining
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Conception Date
—
LMP + 14 days
Key Pregnancy Milestones
| Milestone | Week | Estimated Date |
|---|
Trimester Information
| Trimester | Weeks | Key Events |
|---|---|---|
| First Trimester | 0–13 weeks | Organ development, morning sickness |
| Second Trimester | 14–26 weeks | Movement felt, anatomy scan |
| Third Trimester | 27–40 weeks | Rapid growth, birth preparation |
What is a Pregnancy Due Date Calculator?
The Estimated Due Date (EDD) is calculated using Naegele's Rule: add 40 weeks (280 days) to the first day of your Last Menstrual Period (LMP). This assumes a regular 28-day cycle — cycles longer or shorter than 28 days can shift the due date by a few days.
Beyond the due date, this calculator maps your full pregnancy journey — current gestational week, which trimester you're in, key milestone dates (12-week scan, 20-week anomaly scan, 28-week glucose test), and days remaining until delivery.
lightbulb Example Calculation
Scenario: Mrs. Priya Sharma, 29-year-old teacher from Nagpur — Last Menstrual Period (LMP) started on 10 February 2025, regular 28-day cycle
1EDD = LMP + 280 days = 10 Feb 2025 + 280 days = 17 November 2025
2As of 20 May 2025 → Gestational age = 14 weeks 3 days (2nd trimester)
3Key upcoming milestones: Anomaly scan around 1 July 2025 (20 weeks), glucose test around 22 July 2025
✓ Result: Priya's due date is 17 November 2025. She is currently 14 weeks + 3 days pregnant (2nd trimester).
help_outlineHow to Use the Pregnancy Due Date Calculator
- Enter the date of the first day of your Last Menstrual Period (LMP) — this is the standard medical starting point for all pregnancy dating.
- Enter your average menstrual cycle length in days — the default is 28 days; adjust if your cycle is regularly longer or shorter than this.
- Click "Calculate Due Date" — Naegele's Rule adds 280 days (40 weeks) to your LMP, adjusted for your cycle length, to compute the Estimated Due Date (EDD).
- Review the gestational age (current week and day), trimester, days remaining until due date, and approximate conception date.
- Check the Key Pregnancy Milestones table for important dates — nuchal scan (11–13 weeks), anomaly scan (18–20 weeks), glucose test (24–28 weeks), and more.
Benefits
- Uses Naegele's Rule — the same method employed by OBGYN doctors worldwide for EDD estimation
- Adjusts for non-28-day cycles — longer cycles shift due date forward, shorter cycles back
- Trimester classification shown instantly: First (0–13 weeks), Second (14–26 weeks), Third (27–40 weeks)
- Key antenatal milestone dates pre-calculated — plan NT scan, anomaly scan, and GCT appointments
- Conception date estimated at LMP + 14 days — helpful for correlating with early ultrasound CRL findings
Key Terms
- LMP
- Last Menstrual Period — the first day of your most recent period; standard reference point for pregnancy dating
- EDD
- Estimated Due Date = LMP + 280 days (40 weeks); actual delivery typically occurs within 2 weeks before or after
- Gestational Age
- Number of weeks and days counted from LMP — not from the actual conception date (always 2 weeks ahead of fetal age)
- Naegele's Rule
- EDD = LMP + 9 months + 7 days (or LMP + 40 weeks); standard since 1830; assumes 28-day cycle
- Trimesters
- First: weeks 0–13 (organ development); Second: weeks 14–26 (anatomy scan); Third: weeks 27–40 (growth and birth prep)
quizFrequently Asked Questions
How accurate is this pregnancy due date calculator?
This calculator uses Naegele's Rule — the standard medical method — which assumes a 28-day cycle and ovulation at day 14. Only about 5% of babies are born on the exact due date; most deliveries occur within 2 weeks before or after. Accuracy improves with ultrasound dating using Crown-Rump Length (CRL) measurement in the first trimester (8–10 weeks), because it directly measures embryo size rather than relying on LMP recall. Your OBGYN will confirm and may revise the EDD after the first scan.
What if my menstrual cycle is not 28 days?
The calculator adjusts for non-28-day cycles. For a 35-day cycle (7 days longer than standard), the EDD shifts forward by 7 days. For a 21-day cycle (7 days shorter), EDD moves back by 7 days. Adjustment formula: EDD = LMP + 280 + (Cycle Length − 28) days. If your cycle is irregular or you're unsure of your LMP, first-trimester ultrasound dating (CRL measurement) is the most reliable method for establishing gestational age.
What is the difference between gestational age and fetal age?
Gestational age is counted from LMP — at "12 weeks pregnant," the gestational age is 12 weeks, but the fetus is only about 10 weeks old (fetal age). This 2-week difference exists because LMP typically precedes ovulation (and conception) by approximately 14 days. All medical literature, pregnancy apps, and this calculator use gestational age as the standard measurement — so when your doctor says "12 weeks pregnant," they always mean 12 weeks from LMP.
What are the key antenatal scans and tests in India?
Standard antenatal schedule in India: NT (Nuchal Translucency) scan at 11–14 weeks gestational age — screens for chromosomal abnormalities; Anomaly Scan at 18–20 weeks — checks all fetal organs; Growth Scan at 28–32 weeks; Final scan at 36–37 weeks for fetal position and delivery planning. Blood tests: Dual Marker (11–13 weeks), Quad Marker (15–20 weeks), GCT/OGTT Glucose Challenge (24–28 weeks). All dates align with gestational age from your EDD — the milestones table in this calculator is based on these standard timelines.
Is it normal for delivery to happen before or after the due date?
Yes, completely normal. Only about 5% of babies are born on the exact EDD. Roughly 80% of deliveries occur within 2 weeks of the due date — the "term" window is 37–42 weeks. Deliveries before 37 weeks are preterm; after 42 weeks are post-term. If labour does not start by 41 weeks, your OBGYN may discuss induction options. Plan a 2-week window around your EDD for practical arrangements — hospital bag, maternity leave start date, and childcare planning.