Mr Calcu | Know your estimated due date instantly—plan ahead with confidence and clarity.

Discover your pregnancy due date with our precise calculator. Empower your journey, plan confidently, and feel reassured with accurate delivery insights.

Accurate Pregnancy Due Date Calculator

Pregnancy Due Date Calculator Guidelines

You’ve got this—let’s make calculating your due date easy.

Input the first day of your last menstrual period (LMP) for LMP-based calculations.
Adjust for average cycle length if it's not 28 days to refine your result.
Use ovulation date instead of LMP if you track fertility signs (e.g., LH tests).
For IVF conceptions, input the embryo transfer date and day of embryo development.
Understand that due dates are estimates — only 5% of births occur on the exact day.

Always consult a healthcare provider for personalized guidance and confirmatory scans.

Pregnancy Due Date Calculator Description

Understanding Pregnancy Due Dates

The Pregnancy Due Date Calculator uses medically validated models to estimate your expected delivery date (EDD). Built on Naegele’s Rule and adjusted for cycle variability and ovulation timing, this tool provides enhanced accuracy for different conception scenarios.

Key Concepts

Standard Gestational Period: 280 days (40 weeks) from the first day of the last menstrual period (LMP).
Ovulation-Based Gestation: 266 days from the date of ovulation or conception.
Adjustments: Account for differences in cycle length, implantation time, and fertility treatments like IVF.

Mathematical Models

Base Due Date (EDD) = LMP + 280 days
Cycle Adjustment = (User Cycle Length - 28 days)
Adjusted EDD = Base Due Date + Cycle Adjustment

For ovulation-based models:

EDD = Ovulation Date + 266 days

Pro Tip: If you track ovulation or used IVF, use those dates instead of LMP for greater accuracy.

Edge Cases to Consider

Short Cycles (<21 days): May lead to earlier ovulation and a sooner EDD.
Long Cycles (>35 days): Often associated with delayed ovulation, pushing the EDD later.
Irregular Menstruation: Ovulation tracking is more reliable than LMP in these cases.
Late Implantation: May subtly affect gestational age but not usually the LMP-based EDD.
Multiple Gestation: Expect delivery earlier than the calculated due date (average ~37 weeks for twins).

Case Studies

Case 1: Irregular Cycles, Known Ovulation

Jane has 35-day irregular cycles. She tracked ovulation on May 5, 2025. The calculation becomes:

EDD = May 5, 2025 + 266 days = January 26, 2026

Case 2: IVF with Day-5 Embryo

Maria had a blastocyst (day 5) transferred on April 10, 2025. Her EDD is:

EDD = April 10, 2025 + (266 - 5) = January 1, 2026

Scientific Context

Based on Naegele’s Rule and WHO/ACOG guidelines.
Ideal for personal tracking and clinical use.
Ultrasound dating before 13 weeks provides the highest accuracy if LMP or ovulation are uncertain.

Start planning your pregnancy journey—calculate your due date now and take the next step with confidence.

Example Calculation

Example Calculation Table

Parameter	Example Value
Last Menstrual Period (LMP)	March 1, 2025
Base Due Date (LMP + 280 days)	December 5, 2025
Cycle Length	30 days (Adjustment: +2 days)
Final Due Date	December 7, 2025

Additional Scenarios

Scenario	Input	Resulting EDD
Known Ovulation	Ovulation on May 5, 2025	January 26, 2026
IVF Transfer	Day-5 Embryo on April 10, 2025	January 1, 2026
Short Cycle	25-day cycle (Adjustment: -3 days)	December 2, 2025
Long Cycle	34-day cycle (Adjustment: +6 days)	December 11, 2025

Frequently Asked Questions

It adds 280 days to the first day of your last menstrual period, with adjustments for cycle length variations.

Yes, you can input your average cycle length or ovulation date to refine the estimated due date accordingly.

No, the calculated due date is an estimate; actual delivery may vary based on individual factors.

Use the embryo transfer date and embryo age (e.g., Day 3 or Day 5) to determine a more precise due date.

Because it reflects the duration from fertilization to delivery, excluding the typical 14 days before ovulation in a 28-day cycle.

Ultrasound in the first trimester (before 13 weeks) is often more accurate if LMP is uncertain or cycles are irregular.

Medically, pregnancy is dated from the first day of your last period, but actual conception usually occurs about two weeks later.