Pregnancy Calculator

Understand your pregnancy timeline

Why due dates are estimates

A due date is a best‑fit prediction, not a promise. It assumes a 40‑week pregnancy counted from the first day of the last menstrual period. Many healthy babies arrive before or after the estimated date. Your unique cycle length, ovulation day, and early ultrasounds can refine the estimate.

Calculation methods

• LMP (Last menstrual period): The classic method adds 280 days (40 weeks) to the first day of your last period. If your cycle isn’t 28 days, we adjust by the difference.
• Conception/ovulation date: Adds 266 days (38 weeks) to the conception date, which aligns pregnancy length from fertilization.
• Ultrasound dating: Early scans (especially in the first trimester) can provide a precise gestational age. Enter the scan date and the weeks+days reported.
• IVF transfer: Due date depends on the embryo’s age at transfer. Common approximations: Day‑3 embryo → transfer + 261 days; Day‑5 blastocyst → transfer + 259 days.

Trimesters explained

• Trimester 1 0–13 weeks 6 days: Foundation stage; organ formation and early development.
• Trimester 2 14–27 weeks 6 days: Growth spurt; many feel more energy and first movements (quickening).
• Trimester 3 28–40 weeks: Rapid growth and maturation; prepare for birth.

IVF and ultrasound dating

For IVF, due dates factor in embryo age at transfer. Early ultrasound can re‑date a pregnancy when LMP and scan disagree; this is common and not a cause for concern. Always follow your clinician’s guidance if your official due date differs from app or online calculators.

Helpful tips

• Track dates carefully: Record LMP, positive test date, and scan details to refine estimates.
• Cycle length matters: If your cycle is longer or shorter than 28 days, adjusting the LMP method improves accuracy.
• Expect a range: Most births occur within a window around the EDD. Focus on week‑by‑week progress.
• Use milestones: Schedule checkups and screenings with trimester boundaries in mind.

Safety and limitations

This tool provides educational estimates for global use and does not replace medical advice. If you have symptoms or concerns, consult a qualified healthcare professional. In case of emergencies, seek local care immediately.

Frequently asked questions

• HOW TO calculate my due date from LMP? Add 280 days (40 weeks) to the first day of your last menstrual period. If your cycle isn’t 28 days, adjust by the difference.
• HOW TO use my conception date? Add 266 days (38 weeks) to the conception/ovulation date to estimate your EDD.
• HOW TO handle irregular cycles? Use ultrasound dating if available, or estimate ovulation from your typical cycle length and recalculate.
• HOW TO calculate IVF due date? Day‑3 embryo: transfer + 261 days. Day‑5 embryo: transfer + 259 days.
• HOW TO interpret ultrasound weeks and days? Enter the scan date and the gestational age reported; the calculator will project your EDD.
• HOW TO track trimesters? Trimester 1: 0–13w6d, Trimester 2: 14–27w6d, Trimester 3: 28–40w. The chart shows their relative durations.