Pregnancy Due Date Calculator

What is Pregnancy Due Date Calculator?

The Pregnancy Due Date Calculator estimates your expected delivery date (EDD) based on your last menstrual period (LMP). It shows current pregnancy week, trimester, and key milestone dates throughout the pregnancy.

How to Calculate Due Date

1. Enter the first day of your last menstrual period (LMP)
2. Optionally enter your average cycle length if different from 28 days
3. Click Calculate to see your estimated due date, current week, and trimester milestones

How Pregnancy Due Date Calculator is Calculated

Due Date = LMP + 280 days (40 weeks), based on Naegele's rule. This assumes a regular 28-day cycle. For different cycle lengths, the calculator adjusts by adding or subtracting the difference from 28 days.

Worked Example

LMP: January 15, 2026. Due date = January 15 + 280 days = October 22, 2026. First trimester ends: April 8 (Week 12). Second trimester ends: July 15 (Week 27). Viability: July 1 (Week 24).

Common Use Cases

• Estimating expected delivery date
• Tracking pregnancy progress by trimester
• Planning maternity leave
• Understanding key milestone dates

Common Mistakes to Avoid

• Using conception date instead of LMP — the standard medical calculation uses last menstrual period, not the estimated conception date (which is ~2 weeks later).
• Not adjusting for irregular cycles — if your cycle is 35 days instead of 28, add 7 days to the estimated due date.
• Treating the due date as exact — only about 5% of babies arrive on the due date. Full-term delivery is anywhere from 37 to 42 weeks.
• Panicking if ultrasound dates differ by a few days — a difference of up to 7 days from LMP-based calculation is normal and expected.

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Why Use This Calculator?

Knowing your expected due date helps plan prenatal care, maternity leave, and delivery preparations. The standard Naegele's rule adds 280 days (40 weeks) to the first day of the last menstrual period (LMP). Only about 5% of babies arrive on the exact due date — the normal range is 37-42 weeks.

What This Tool Offers

• Due date from LMP or conception date
• Current trimester and week identification
• Key milestone dates (ultrasound, glucose test)
• Weight gain tracker by trimester
• Baby size comparison by week
• Maternity leave planning

Calculation Method

EDD (Naegele's Rule) = LMP + 280 days. Alternative: LMP + 7 days – 3 months + 1 year. From conception: + 266 days.

Worked Example

LMP: 15 January 2026. EDD = 15 Jan + 280 days = 22 October 2026. Week 12 ultrasound: ~8 April 2026. Glucose test: ~8 July 2026.

Quick Reference Data

Key pregnancy milestones by week

Expert Tips

• 💡 First ultrasound (6-8 weeks) gives the most accurate due date — more reliable than LMP.
• 💡 Normal pregnancy: 37-42 weeks. Pre-term: <37 weeks. Post-term: >42 weeks.
• 💡 Take 400 mcg folic acid daily from conception through first trimester.
• 💡 Indian government provides 26 weeks maternity leave under the 2017 amendment.
• 💡 Schedule glucose tolerance test between weeks 24-28.

Who Is This For?

Expecting parents, gynecologists, midwives, and HR departments planning maternity leave.