Pregnancy Due Date Calculator [2026]

Free Pregnancy Due Date Calculator for Your Website

A pregnancy due date calculator estimates the expected delivery date and key pregnancy milestones based on the first day of the last menstrual period (LMP), conception date, or ultrasound measurements. This essential maternal health tool provides expectant parents and healthcare providers with a standardized timeline for fetal development stages, trimester transitions, recommended prenatal screenings, and anticipated birth window. Whether you’re an OB/GYN office providing patient education resources, a pregnancy tracking app delivering personalized milestone notifications, a maternal health blog offering week-by-week pregnancy guides, a fertility clinic supporting newly pregnant patients, or a doula service helping families prepare for birth, this calculator transforms simple date inputs into comprehensive pregnancy timelines that reduce anxiety, facilitate planning, and ensure timely prenatal care throughout the 40-week journey.

How to Use This Pregnancy Calculator

Users can calculate their due date using one of three methods: (1) First day of last menstrual period (LMP) - the most common method, adding 280 days (40 weeks) from LMP, (2) Known conception date - adding 266 days from conception, or (3) Ultrasound-based due date - entering the estimated due date provided by early pregnancy ultrasound (most accurate method, especially for irregular cycles). Enter the relevant date, and the calculator applies Naegele’s Rule or adjusts based on conception date. Results display estimated due date, current pregnancy week and day, trimester milestones, conception date estimate (if calculated from LMP), and a timeline of important prenatal appointments and screenings.

Benefits of Adding This Calculator to Your Website

• Patient Education: Empower expectant parents with clear timeline expectations and reduce the volume of basic questions about pregnancy dating
• Appointment Scheduling: Help patients understand when key screenings should occur, improving prenatal care compliance
• Content Personalization: Use calculated due dates to recommend relevant content for current pregnancy stage
• Lead Generation: Capture contact information from expectant parents interested in week-by-week pregnancy updates or birth preparation resources
• Trust Building: Demonstrate medical accuracy and attention to maternal health needs, positioning your practice or service as a reliable resource

Use Cases for Pregnancy Calculators

Obstetrics and Gynecology Practices: Provide patients with standardized pregnancy dating between initial confirmation and first prenatal appointment. Calculate scheduling for routine prenatal visits (every 4 weeks until 28 weeks, every 2 weeks until 36 weeks, weekly until delivery), first-trimester screening (10-14 weeks), anatomy scan (18-22 weeks), glucose screening (24-28 weeks), and Group B Strep testing (36-37 weeks). Help patients understand that “due date” represents estimated delivery window (only 5% deliver exactly on due date, while 90% deliver between 37-42 weeks).

Pregnancy and Parenting Apps: Integrate due date calculations into user onboarding to personalize the entire app experience. Deliver week-by-week pregnancy content matched to current gestational age, countdown timers to due date and key milestones, trimester-specific symptom trackers, and appointment reminders for prenatal screenings. Calculate and display fetal development milestones (heart starts beating at 6 weeks, movement felt at 16-25 weeks, lungs mature at 36 weeks) and corresponding maternal body changes.

Fertility Clinics and Reproductive Endocrinologists: Calculate due dates for IVF pregnancies using embryo transfer date (IVF due dates are more precise than LMP-based calculations since conception timing is known). Provide realistic timeline expectations for patients transitioning from fertility treatment to prenatal care. Calculate when to schedule first ultrasound (typically 6-8 weeks from LMP) to confirm pregnancy viability and accurate dating.

Doulas and Birth Educators: Help clients understand their pregnancy timeline and plan for childbirth education classes (typically taken in third trimester), birth plan discussions, and postpartum preparation. Calculate optimal timing for hiring doula services (second trimester) and beginning birth preparation (third trimester). Provide realistic expectations about due date variability and when to expect labor onset.

Maternal Health Content Sites and Bloggers: Personalize pregnancy content by allowing readers to calculate their due date and receive customized week-by-week pregnancy information. Create email sequences triggered by calculated due date that deliver relevant content for each pregnancy stage. Recommend products, services, and resources appropriate for current trimester (first trimester: prenatal vitamins, morning sickness remedies; second trimester: maternity clothes, prenatal classes; third trimester: hospital bags, birth plans, postpartum supplies).

Employer Benefits and HR Departments: Help expecting employees plan maternity leave by calculating anticipated delivery date and standard leave windows (typically starting 2-4 weeks before due date). Calculate FMLA eligibility dates, short-term disability claim timing, and return-to-work planning. Provide resources for pregnancy accommodation requests and workplace rights during pregnancy.

Health Insurance Providers: Calculate enrollment periods for adding newborns to insurance plans (typically within 30 days of birth). Provide timeline for prenatal care coverage and recommended screening schedules. Estimate delivery costs and out-of-pocket expenses based on due date and plan year deductibles.

Key Features

The pregnancy calculator applies Naegele’s Rule for LMP-based calculations (add 7 days to first day of LMP, subtract 3 months, add 1 year - equivalent to adding 280 days). For known conception dates, it adds 266 days (38 weeks). It divides pregnancy into three trimesters (first: weeks 1-12, second: weeks 13-26, third: weeks 27-40) and displays current gestational age in weeks and days. Advanced versions may include fetal development milestone descriptions, recommended prenatal appointment schedules, screening test windows, weight gain tracking, contraction timers for labor onset, and countdown to due date. Some calculators adjust for average menstrual cycle length (standard calculations assume 28-day cycle) or calculate multiple gestation timelines for twins/multiples.

Create Your Own Health Calculator

With Appizy, you can convert your Excel spreadsheet into an interactive web calculator in minutes. No coding required - just upload your spreadsheet and get an embed code.

Perfect for: OB/GYN practices, midwives, doulas, pregnancy apps, maternal health bloggers, fertility clinics, and lactation consultants

Key features:

• No coding required - use your existing Excel formulas
• Fully customizable to match your brand
• Mobile-responsive design
• Secure, privacy-focused (no data stored)
• Easy embed on any website platform

Create your calculator - Start free today!