Pregnancy Due Date Calculator (EDD)

How to Use Pregnancy Due Date Calculator (EDD)

1. Step 1: Choose a method

   Select LMP, Ultrasound, or Conception/IVF to match the information you have.

2. Step 2: Enter your date(s)

   Provide your LMP date (and cycle length), ultrasound GA + scan date, or conception/transfer date.

3. Step 3: Check your estimate

   See the estimated due date (EDD), today’s gestational age, and current trimester.

4. Step 4: Review milestones

   Open the milestones list for trimester boundaries, anatomy scan window, and the full‑term range.

5. Step 5: Save or share

   Use “Add EDD to calendar” or “Copy summary” to keep dates handy.

Key Features

• EDD by LMP (cycle‑length aware)
• EDD by ultrasound (GA at scan)
• Conception & IVF (day‑3/day‑5)
• Gestational age & trimester today
• Milestones & calendar export

Understanding Results

Formula

The calculator uses standard obstetric rules. For LMP dating, EDD = LMP + 280 days (40 weeks). If your usual cycle isn’t 28 days, we shift the estimate by the difference: longer cycles move EDD later; shorter cycles move it earlier. For ultrasound dating, we take the scan date and the gestational age reported on that day, then project forward to 40 weeks. For conception‑based dating, EDD is 266 days after conception. IVF transfers mirror clinic practice: add 263 days to a day‑3 transfer or 261 days to a day‑5 transfer.

Reference Ranges & Interpretation

EDD is a midpoint. Most births cluster in a window, not on the dot. Many clinicians describe “term” as a range: roughly 37–41+ weeks, with 39–40 weeks often called full term. Early ultrasounds (first trimester) tend to be the most precise single data point; later measurements have wider normal ranges. If your clinician assigned or revised your EDD, rely on that date for scheduling and questions.

Assumptions & Limitations

Cycle‑length adjustments assume ovulation usually occurs about 14 days before the next period. Irregular cycles, uncertain dates, multiple gestations, and late first visits can shift accuracy. The tool is informational and not medical advice. When in doubt, use the EDD in your medical chart.

Complete Guide: Pregnancy Due Date Calculator (EDD)

Use our pregnancy due date calculator to estimate your EDD from LMP, ultrasound, or conception/IVF. See gestational age, trimester dates, and calendar export.

The goal is simple: give you a clear, calendar‑friendly estimate and the most useful dates around it. The pregnancy due date calculator supports three common ways to date a pregnancy — last menstrual period (LMP), early ultrasound, or conception/IVF — because different people start with different information. Your results show the estimated due date (EDD), today’s gestational age, trimester, and a short list of helpful milestones you can add to your own calendar.

How the pregnancy due date calculator works

A due date is an estimate — the midpoint of an expected window. The classic approach is Naegele’s rule: add 280 days (40 weeks) to the first day of your last menstrual period. If your cycle isn’t 28 days, we adjust the estimate by the difference. For example, if your cycle averages 32 days, ovulation likely happens a few days later, so we shift the due date later as well. If your cycle averages 26 days, we shift a bit earlier.

Ultrasound‑based dating uses the gestational age reported by the sonographer on the day of your scan. Because fetal measurements are especially consistent early on, a first‑trimester ultrasound is often the most accurate single data point. Our tool takes the scan date, subtracts how far along the measurement says you were, and projects forward to 40 weeks to give your EDD. Conception‑based inputs use the common obstetric convention: EDD is 266 days after conception. For IVF transfers, we use real‑world clinic rules — add 263 days for a day‑3 embryo or 261 days for a day‑5 blastocyst — which line up with standard practice.

The calculator then summarizes today’s gestational age, highlights which trimester you’re in, and lists several anchors (end of the first trimester, typical anatomy scan window, third‑trimester start, full‑term window, and your EDD). Each one is shown as a date so you can plan without doing mental math. You can copy the summary or export the due date as a calendar file to drop into your phone.

LMP and cycle‑length adjustments

If you know the first day of your last period and your typical cycle length, LMP dating is fast and reasonable. The usual rule is EDD = LMP + 280 days when your cycle averages 28 days. Because ovulation often happens about 14 days before the next period, longer cycles tend to shift conception later; shorter cycles shift earlier. Our LMP mode lets you adjust the cycle length so the projection better matches your usual timing. This small tweak matters for people who naturally run 25‑ or 32‑day cycles — it can change the estimate by a few days.

If your cycles vary a lot, treat the result as a helpful center point rather than a promise. Many people use the pregnancy week calculator alongside this page to see where today lands on the week‑by‑week map. If you are still planning a pregnancy and want to predict your next period or a likely fertile window, try the period calculator or the period tracker — both are simple, private, and mobile‑friendly.

EDD from ultrasound measurements

Ultrasound dating uses fetal measurements to estimate how far along the pregnancy is on the day of the scan. In the first trimester, crown–rump length (CRL) is the workhorse because embryos grow at a predictable pace. Later in pregnancy, head, abdomen, and femur measurements help cross‑check growth, but the window of normal becomes wider, so estimates carry more spread. In practice, a precise early ultrasound can refine or confirm an LMP‑based estimate if the difference is large enough.

To use this mode, enter your scan date and the gestational age reported (for example, 11 weeks 5 days). The calculator simply moves forward from that point to 40 weeks to produce your EDD. If your clinician officially changed your EDD based on the scan, rely on the clinic’s value. Ultrasound dating reflects what was measured in real time and is often the preferred basis when it disagrees meaningfully with LMP.

IVF and embryo transfer dating

People who used IVF or frozen embryo transfer usually receive a written due date from their clinic. If you want to double‑check or add your date to a calendar, the calculator can reproduce the standard method: add 263 days to a day‑3 transfer or 261 days to a day‑5 (blastocyst) transfer. If you have an exact conception date (e.g., from insemination timing), adding 266 days aligns with common obstetric practice. These rules echo how clinics map lab dates to the familiar 40‑week schedule used in prenatal care.

Remember that clinics may still adjust a transfer‑based estimate if a very early ultrasound suggests a different timeline. That is not an error; the point is to keep the EDD consistent with how the pregnancy itself is developing rather than to defend one source forever. If you have a clinic‑assigned EDD, treat it as the primary reference for scheduling.

Irregular cycles: what to do

Many cycles aren’t clockwork, and that’s okay. If your cycle length varies widely month to month, an LMP guess is still helpful but may be off by several days either way. In that case, an early ultrasound is usually the cleanest way to pin the estimate. You can still enter your best LMP, but put more weight on a scan‑based EDD if your clinician provides one.

If you’re early and deciding when to test, the pregnancy test calculator can help pick a day with a good chance of detection. Later, if you want a quick status check any time, use the pregnancy week calculator to see your current week and upcoming milestones without re‑entering every detail here.

What a due date really means

“Due date” is a midpoint, not a deadline. Most full‑term births fall in a window rather than on the exact day. Many clinicians frame “term” as a broad range with different labels: early term around 37–38 weeks, full term around 39–40 weeks, and late term beyond 41 weeks. Your baby can arrive before or after the date shown. If plans change — induction, scheduled cesarean, or a new clinical finding — your care team will set timing with your bigger picture in mind.

This is why the calculator lists key dates around the EDD instead of showing a single number in isolation. Knowing when the first trimester ends, when many anatomy scans occur, and when the third trimester begins helps you plan work, travel, supplies, and support. If you want those ranges in a tidy view, the trimester calculator lays out each trimester’s dates from your EDD or LMP, all in one place.

Trimester boundaries and milestones

For planning, a simple trimester map is often the most helpful. The first trimester runs from week 0 through 13 weeks and 6 days. The second trimester runs from 14 weeks through 27 weeks and 6 days. The third trimester starts at 28 weeks and continues through delivery. Somewhere around 18–22 weeks, many clinics schedule the detailed anatomy scan. Near 24–28 weeks you may see glucose screening on the calendar. As you approach 36–37 weeks, some practices begin weekly visits. These patterns vary, but having rough anchors in mind makes the flow less mysterious.

If you want a week‑by‑week map that updates as time passes, open the pregnancy week calculator. If you are tracking weight, the pregnancy weight gain calculator and pregnancy weight calculator show recommended ranges by BMI with trimester targets. These tools are informational — they don’t diagnose or treat — but they help you prepare and ask great questions during visits.

Why your due date might change

It’s common for a clinician to adjust the EDD early on if a precise ultrasound suggests a different timeline. That isn’t a setback; it’s a refinement based on better information. Early measurements (like first‑trimester CRL) are more uniform than later ones, so most revisions happen before the anatomy scan. Once an EDD is set from a reliable source, teams usually keep it stable to avoid confusion in later planning. If your chart lists a new EDD, use that date in your personal planning and in any other tools you open.

If your pregnancy is past the EDD, your care team will consider your overall health, baby’s well‑being, and local practice patterns when discussing next steps. Some clinics schedule extra monitoring after a certain point. Others may offer induction. There isn’t a single right answer for everyone; it’s a conversation guided by your specific situation.

Planning checklist and reminders

Dates are useful because they simplify planning. Here are practical prompts people often appreciate as weeks go by:

• Save your due date to your calendar and set a reminder a few weeks before it.
• Note trimester transitions so supplies, travel, and work plans aren’t last‑minute.
• Sketch a simple checklist for the 20‑week anatomy scan (questions, logistics, child care, parking).
• Plan time for glucose screening around 24–28 weeks if your clinic uses it.
• Start thinking about leave plans early — even if they change later.
• Keep notes on how you feel; patterns help you ask specific questions at visits.

Preferences and traditions differ widely. Some people choose a minimal approach and keep only appointments on the calendar. Others enjoy mapping everything out. Either way is fine. The calculator’s copy and calendar export options exist so you can organize things your way without retyping dates after every change.

Helpful tools to use together

• Pregnancy Week Calculator — shows current week, milestones, and a simple timeline.
• Trimester Calculator — lays out first, second, and third trimester dates clearly.
• Pregnancy Weight Gain Calculator — trimester targets by BMI category.
• Pregnancy Weight Calculator — total gain range and planning tips.
• Pregnancy Test Calculator — helpful if you’re still early and timing a test.

We keep tools simple, mobile‑first, and private. Nothing you enter is stored on our servers.

Scope and limitations

This calculator is for general planning. It is not medical advice and cannot diagnose any condition. Dating conventions describe averages across many healthy pregnancies; individual care should reflect your history and your clinician’s judgment. If you have questions about your EDD, or if the calculator and your chart disagree, always use the EDD in your medical record.

If the dates you enter don’t fit your situation (uncertain LMP, irregular cycles, IVF with unique protocols, or a late initial visit), rely on your clinician’s guidance. The numbers here are transparent and practical so you can plan, ask better questions, and stay organized through a special season of life.

Frequently Asked Questions