Estimated Due Date
{{ dueDateText }}
{{ weeks }} wks {{ daysLeft }} days left {{ trimester }} trimester
dd/mm/yyyy
days
  • Due date{{ dueDateText }}
  • Gestation{{ days }} days ({{ weeks }} wks)
  • Remaining{{ daysLeft }} days
  • {{ t.label }}{{ t.start }} – {{ t.end }}
WeekStartsEnds
{{ row.w }} {{ row.s }} {{ row.e }}
MilestoneDate
{{ m.name }}{{ m.date }}
{{ sizeWeek }}
Length{{ lengthDisplay }}
Weight{{ weightDisplay }}
Categories: Calculator , Health & Fitness
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Your estimated due date indicates when pregnancy reaches full term, calculated from either the first day of your last menstrual period or the known conception date. Healthcare professionals use this benchmark to schedule prenatal screenings, monitor fetal development, plan maternity leave, and arrange delivery logistics, making accurate calculation valuable for expectant parents and clinicians.

This calculator automates standard obstetric formulas with a reactive interface that updates instantly as you adjust starting method, date, or cycle length. Behind the scenes it performs date arithmetic entirely inside your browser, renders progress indicators, and offers downloadable CSV timelines, allowing frictionless exploration without sending personal information to any server.

Easily explore weekly milestones, trimester boundaries, and fetal size estimates to support appointment scheduling, birth preparation, insurance planning, and family discussions. Always verify results with a qualified healthcare provider before making medical or lifestyle decisions based on these figures, because individual circumstances vary. This calculator offers informational estimates, not medical advice.

Technical Details:

The tool executes entirely client-side using a lightweight reactive engine and the browser’s native Date object. Inputs bind to computed properties that recalculate gestational metrics on every change, ensuring sub-millisecond feedback. No external API calls occur, so reproductive data never leaves your device.

Dual Input Modes

Select either Last period or Conception date to match personal records and clinical guidance.

Adjustable Cycle Length

Override the default 28-day cycle to refine the due-date offset for shorter or longer natural cycles.

Interactive Progress Indicators

Badges, trimester labels, and a progress bar recalculate instantly, giving clear visual cues for weeks elapsed and days remaining.

Exportable Timeline

Create a detailed week-by-week CSV schedule with one click for easy sharing, printing, or spreadsheet analysis.

Fetal Size Estimator

Slide to any week between 5-40 and view median length and weight in metric or imperial units to contextualise growth.

Calculations & Scoring:

Two established obstetric formulas underpin the calculator. All arithmetic occurs locally for privacy.

ScenarioFormula
Last period methodDue Date = LMP + 280 days − (28 − Cycle)
Conception date methodDue Date = Conception + 266 days

All dates convert to ISO strings, then display with the browser locale for familiarity. No data is stored or transmitted.

Step-by-Step Guide:

Follow these quick steps to obtain a personalised timeline.

  1. Choose Method from the dropdown to match your available information.
  2. Enter the relevant Date in the calendar field labelled dd/mm/yyyy.
  3. Optional: adjust Cycle length to reflect personal averages.
  4. Review the summary panel for due-date, weeks, and progress bar.
  5. Select Timeline, Milestones, or Fetal Size tabs to explore advanced views.
  6. Press Download CSV in the Timeline tab to export the schedule.

FAQ:

Common questions about functionality, accuracy, and privacy.

How accurate is the due date?

Dates follow clinical standards but can vary with individual pregnancy factors; your provider may adjust based on ultrasounds.

What if my cycle is irregular?

Enter your average cycle length for a closer approximation, then confirm with early ultrasound measurements.

Can I switch units?

Yes; toggle the Metric / Imperial switch in the Fetal Size tab to convert length and weight instantly.

Is my data stored?

No. All inputs and calculations happen in your browser memory and disappear when you close the page.

Do I need an internet connection?

The tool loads once from the site, then functions fully offline, making it reliable in clinical areas with limited connectivity.

Troubleshooting:

Resolve common issues quickly.

Blank results — ensure a valid date is selected and the page has fully loaded.

Incorrect due date — confirm the chosen method and cycle length match your situation.

Progress bar stuck at 0 % — check that today’s date on your device is correct.

CSV not downloading — verify pop-up blockers allow file downloads from this site.

Numbers appear in imperial units — toggle the Metric / Imperial switch to change display.

Advanced Tips:

Leverage hidden capabilities for deeper insight.

  • Bookmark the page after setting parameters; query strings retain your selections on reload.
  • Use the timeline CSV in spreadsheet software to chart symptom entries alongside gestational weeks.
  • Compare trimester dates with local public-holiday calendars to plan leave strategically.
  • Switch units to match clinical growth charts for direct comparison.
  • Share the milestone list with family members to coordinate appointments and support plans.

Glossary:

Key terms you may encounter.

EDD
Estimated Date of Delivery, calculated prediction of birth.
LMP
First day of the Last Menstrual Period.
Gestation
Elapsed time since conception, measured in weeks plus days.
Trimester
One-third of pregnancy, roughly 13-week segments.
Viability
Stage when a fetus can potentially survive outside the womb.
No data is transmitted or stored server-side.
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