Pregnancy Due Date, Conception, Weight Gain & Ovulation Calculator

Estimate obstetric due date (40 weeks), ovulation/conception date, menstrual cycle interval, and IOM pregnancy weight gain range.

Estimated Obstetric Due Date (40 Weeks Gestation)
2027-03-08
Est. Ovulation / Conception Date: 2026-06-15 • Next Cycle Start: 2026-06-29
Estimated Ovulation / Conception 2026-06-15
Next Menstrual Period Date 2026-06-29
IOM Recommended Total Weight Gain 11.5 – 16.0 kg (25 – 35 lbs)
Standard Term Duration 280 days (40 wks)
Inputs
Start date of most recent menstrual cycle (YYYY-MM-DD).
days
Standard reference cycle is 28 days (adjusts luteal ovulation timing).
kg/m²
Used to look up Institute of Medicine (IOM) singleton weight gain guidelines.
Results & Graph
Estimated Obstetric Due Date (40 Weeks Gestation)
2027-03-08
Est. Ovulation / Conception Date: 2026-06-15 • Next Cycle Start: 2026-06-29
Estimated Ovulation / Conception
2026-06-15
Fertile window: ±3 days
Next Menstrual Period Date
2026-06-29
28-day cycle
IOM Recommended Total Weight Gain
11.5 – 16.0 kg (25 – 35 lbs)
For pre-pregnancy BMI 22
Standard Term Duration
280 days (40 wks)

40-Week Gestational Trimester Timeline (Weeks)

First Trimester (Weeks 1–13), Second Trimester (Weeks 14–27), Third Trimester (Weeks 28–40)
Graph 1 • 40-Week Obstetric Trimester & Milestone Timeline LMP, Conception, Anatomy Scan, and Estimated Due Date
Trimester 1 (Wks 1–13) Trimester 2 (Wks 14–27) Trimester 3 (Wks 28–40) Wk 0: LMP ▲ Wk 2: Conception ▲ Wk 20: Anatomy Scan Wk 40: EDD (2027-03-08) Naegele’s Rule: LMP + 280 Days + (28 − 28) Day Cycle Adjustment
Graph 2 • 28-Day Menstrual Cycle & 6-Day Fertile Window Ovulation occurs ~14 days before next period (Day 14)
Menstrual / Follicular 1 6-Day Fertile Window 9 14-Day Luteal Phase 15 28 14 Day 14
Graph 3 • IOM Trimester-by-Trimester Cumulative Weight Gain (kg) Institute of Medicine singleton pregnancy reference trajectory
0 kg 7.5 kg 14.9 kg Wk 0: 0 kg 0 Wk 0 Wk 12 (T1): 1.8 kg 1.8 Wk 12 (T1) Wk 20: 5.2 kg 5.2 Wk 20 Wk 28 (T2): 8.8 kg 8.8 Wk 28 (T2) Wk 34: 11.4 kg 11.4 Wk 34 Wk 40 (EDD): 13.8 kg 13.8 Wk 40 (EDD)
Summary: Estimated Due Date is 2027-03-08 and estimated ovulation date is 2026-06-15.
Summary: Based on a Last Menstrual Period (LMP) of 2026-06-01 and a 28-day cycle, ovulation/conception is estimated around 2026-06-15 and the 40-week Estimated Due Date (EDD) is 2027-03-08. For a pre-pregnancy BMI of 22 kg/m², the Institute of Medicine (IOM) singleton gestational weight gain guideline is 11.5 – 16.0 kg (25 – 35 lbs).
⚠️ Obstetric Clinical Notice: Naegele’s Rule and luteal-phase ovulation calendars provide population-average timeline estimates. First-trimester crown-rump length (CRL) ultrasound by an OB/GYN is the clinical gold standard for gestational dating.

Formula & Mathematical Methodology: Cycle-Adjusted Naegele’s Rule & Luteal Phase Ovulation

EDD = LMP + 280 days + (Cycle Length − 28),   Ovulation = LMP + (Cycle Length − 14)
EDD = LMP + 280 days + (CycleLength − 28); Ovulation = LMP + (CycleLength − 14) days
  • LMP: First day of the Last Menstrual Period
  • 14 days: Standard 14-day luteal phase preceding the next menstrual period

Rounding: Exact UTC calendar day arithmetic.

Worked Example: LMP of 2026-06-01 with a 28-Day Cycle and Pre-Pregnancy BMI of 22

Compute estimated ovulation date, 40-week due date, and IOM weight gain range.

  1. Estimated ovulation / conception = 2026-06-01 + 14 days = 2026-06-15.
  2. Estimated 40-week Due Date (EDD) = 2026-06-01 + 280 days = 2027-03-08.
  3. For BMI 22 (18.5–24.9 normal range), IOM singleton weight gain guideline is 11.5 – 16.0 kg (25 – 35 lbs).
Result: Estimated Due Date is 2027-03-08; ovulation around 2026-06-15.

Frequently Asked Questions

Why is pregnancy counted as 40 weeks from LMP if conception happens 2 weeks later?

Obstetric gestational age is traditionally measured from the first day of the Last Menstrual Period (LMP) because LMP is a known calendar date, making 40 weeks of gestational age equal to roughly 38 weeks of fetal post-conception age.

Health & Fitness • Maternal Health & Cycle Planning Guide

How to Use the Pregnancy Due Date, Conception, Weight Gain & Ovulation Calculator: Practical Guide & Visual Analysis

Calculate key obstetric and reproductive calendar milestones from the first day of your Last Menstrual Period (LMP) and average cycle length, alongside Institute of Medicine (IOM) weight gain ranges. Whether you are researching pregnancy calculator, due date calculator, ovulation calculator, conception calculator, period calculator, this interactive tool helps you calculate Estimated Due Date (EDD) via Naegele’s rule, estimated ovulation/conception window, next menstrual period date, and IOM gestational weight gain guidelines.

Interpreting the 3 Custom Visual Graphs & Key Outputs

As you adjust First Day of Last Menstrual Period (LMP), Average Menstrual Cycle Length, Pre-Pregnancy BMI (For IOM Weight Gain), the calculator immediately computes Estimated Due Date (40 Weeks), Estimated Ovulation / Conception Date, Next Menstrual Period Start Date, IOM Recommended Gestational Weight Gain and updates all three domain-specific SVG charts in real time. Instead of relying on a single static figure, you can inspect the primary domain diagram, component breakdown, and multi-point trajectory curve to see how changing your inputs shifts the final result. Use the Compare (up to 3 scenarios) button to evaluate side-by-side variations before making a decision.

Real-World Benchmark & Planning Tips (Global (ACOG / WHO / IOM Reference))

In our benchmark scenario (LMP of 2026-06-01 with a 28-Day Cycle and Pre-Pregnancy BMI of 22), Estimated Due Date is 2027-03-08; ovulation around 2026-06-15. Keep in mind that assumes a 14-day luteal phase between ovulation and the next period. For related calculations in Health & Fitness, explore Age Calculator, Date Difference & Business Days Calculator, BMI Calculator (Body Mass Index).