Due Date Calculator – Estimate Your Pregnancy Due Date
Estimate your baby\u2019s due date and key pregnancy landmarks.
About the Due Date Calculator
What is the Due Date Calculator?
A due date calculator estimates your baby\u2019s due date from the first day of your last period or a known conception date.
Why use this calculator?
The due date schedules scans, maternity notes and your preparation timeline. It is an estimate that the whole maternity team works around.
How to use it
- Enter the first day of your last period (or a conception date).
- Adjust cycle length if it differs from 28 days.
- Read the due date and trimester landmark dates.
Formula
Due date = LMP + 280 days (about 40 weeks).
First ultrasound dating is the most accurate estimate; use it once available.
Frequently Asked Questions
When are most babies actually born?
Most babies arrive between 38 and 41 weeks. Being early or late by a couple of weeks is completely normal.
Why do LMP and scan dates differ?
Cycle length and ovulation timing vary. The scan measures fetal size and is generally considered more accurate.
Does it account for leap years?
Yes. The date logic follows the Gregorian calendar, including leap years and differing month lengths.
Are weekends and holidays excluded?
Only if the calculator says so. By default, results count every calendar day; use a business-day option where available.
Which time zone is used?
Calculations use whole calendar dates and are time-zone independent unless a time-of-day is involved.
Is this a medical diagnosis?
No. This tool provides general wellness information only. It is not a substitute for evaluation by a qualified healthcare professional.
Why do results differ from my doctor's measurements?
Clinical measurements use calibrated equipment and professional technique. Home estimates rely on formulas and self-reported values, so small differences are normal.
How often should I recalculate?
Recheck after meaningful changes such as weight gain or loss, a new workout routine, or every few months to track trends over time.
Do these formulas apply to everyone?
Most population formulas are less accurate for athletes, pregnant people, very young children and the elderly. Use them as a general guide.
Is this calculator free to use?
Yes. Every calculator on this site is completely free, with no hidden fees, no subscriptions and no limits on how many times you can use it.