Gestational Age & Due Date Calculator (LMP/EDD)
Calculate current pregnancy weeks, estimated due date (EDD), conception date, and trimester milestones using standard Naegele's rule and ACOG dating criteria.
Calculate Your Gestational Age
Estimate gestational age, due date, and trimester using standard pregnancy dating methods.
The first day your most recent menstrual period started
Days (21\u201335). Affects the estimated conception date only.
Your estimated due date (can be in the past or future)
The estimated date of conception (approximate, cannot be in the future)
Quick Summary
Clinically validated obstetric calculator supporting Last Menstrual Period (LMP), Ultrasound dating, and Conception date modes. Calculates current gestational age in exact weeks and days.
How It Works
- Select your calculation method — Choose from Last Menstrual Period (LMP), Estimated Due Date (EDD), or Conception Date.
- Enter your date — Enter the required date (LMP, EDD, or conception date) based on the selected method.
- Optionally enter your cycle length — For LMP mode, you can adjust the average menstrual cycle length (default 28 days, range 21–35) for a more precise conception date estimate.
- Review your results — The calculator displays the estimated gestational age in weeks and days, due date, conception date, trimester, current week, days remaining, and a pregnancy timeline.
Formula Used
The calculator uses standard pregnancy dating formulas based on established obstetric practice:
- LMP Mode: Gestational age = Current date − LMP. Due date = LMP + 280 days. Conception date = LMP + (Cycle length − 14) days.
- EDD Mode: LMP = EDD − 280 days. Gestational age = Current date − LMP. Conception = LMP + 14 days.
- Conception Mode: LMP = Conception date − 14 days. Due date = LMP + 280 days. Gestational age = Current date − LMP.
The 280-day (40-week) gestational duration is based on Naegele’s rule, the standard obstetric method for estimating due dates used by the American College of Obstetricians and Gynecologists (ACOG).
Evidence
The gestational age dating methods used by this calculator are based on standard obstetric conventions and Naegele’s rule:
- The American College of Obstetricians and Gynecologists (ACOG) recognizes LMP-based dating as a standard method for estimating gestational age and due dates, with first-trimester ultrasound providing the most accurate confirmation
- The Cleveland Clinic publishes patient education on due date calculation and gestational age assessment based on LMP and Naegele’s rule
- The Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD/NIH) provides educational content on pregnancy, childbirth, and prenatal care
- MedlinePlus (National Library of Medicine / NIH) defines gestational age as the age of a pregnancy measured from the first day of the LMP to the current date
- The Centers for Disease Control and Prevention (CDC) uses LMP-based dating for pregnancy surveillance and provides pregnancy health resources
Naegele’s rule (LMP + 280 days) is the standard formula for estimating due dates in obstetric practice, endorsed by ACOG and used internationally.
How to Interpret Your Results
The calculator provides educational estimates of pregnancy dates based on the information you entered:
- Gestational Age — The estimated pregnancy duration in weeks and days, calculated from the LMP date to the current date. This is the standard method for expressing how far along a pregnancy is.
- Estimated Due Date — The estimated date of delivery based on LMP + 280 days (40 weeks) using Naegele’s rule. Actual delivery dates vary.
- Estimated Conception Date — The estimated date of fertilization. In LMP mode, this is calculated using the cycle length offset. In EDD and conception modes, the standard 14-day offset is used.
- Pregnancy Trimester — The educational trimester classification based on gestational age (First: conception to 13 weeks, Second: 14–27 weeks, Third: 28 weeks onward).
Important: These estimates are for informational purposes only. Gestational age and due dates are best determined by early ultrasound and clinical assessment. The calculator does not confirm pregnancy, predict delivery dates, or replace prenatal care. If you have questions about your pregnancy dates, consult a qualified healthcare professional.
Medical Disclaimer
The information provided by Qurekit's calculators is for educational and informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition or treatment. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.
Frequently Asked Questions
Medical References
- American College of Obstetricians and Gynecologists (ACOG) — Methods for Estimating the Due Date
- Cleveland Clinic — Due Date Calculator: How Many Weeks Pregnant Are You?
- Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD/NIH) — Pregnancy and Childbirth
- MedlinePlus (National Library of Medicine / NIH) — Gestational age
- Centers for Disease Control and Prevention (CDC) — Pregnancy
Related Tools
Version History
Every version is logged with its build date, changes, and evidence sources so you can verify the methodology.
Version v1.0.0
Initial Implementation
Initial implementation of the Gestational Age Calculator. Estimates gestational age using standard pregnancy dating methods with support for Last Menstrual Period (LMP), Estimated Due Date (EDD), and Conception Date calculation modes. Includes trimester assignment and a pregnancy timeline visualization.
Changes
- Three calculation modes: LMP, EDD, and Conception Date
- LMP mode with optional cycle length adjustment (21–35 days)
- Gestational age calculation in weeks and days
- Estimated due date calculation using Naegele's rule (LMP + 280 days)
- Estimated conception date calculation
- Pregnancy trimester assignment (First, Second, Third)
- Days remaining until due date
- Current pregnancy week display
- Pregnancy timeline visualization with LMP, conception, today, and due date markers
- Educational interpretation of calculated dates
- Medical disclaimer always visible with results
- Medical references section with authoritative sources (ACOG, MedlinePlus, NICHD, CDC, Cleveland Clinic)
- FAQ section with 6 educational questions
- Structured data (WebApplication, MedicalWebPage, FAQPage)
- BreadcrumbList JSON-LD for SEO
- Accessibility: keyboard navigation, aria-live, aria-invalid, focus management
- Mobile-responsive layout
- Related tools carousel
Evidence Sources
- American College of Obstetricians and Gynecologists (ACOG)
- Cleveland Clinic
- Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD/NIH)
- MedlinePlus / National Library of Medicine (NIH)
- Centers for Disease Control and Prevention (CDC)