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Utilnivo

Pregnancy Due Date Calculator

Estimate a due date from the start of the last period.

No registration
  • On your device

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What is a pregnancy due date calculator?

A due date calculator estimates your baby's due date from the first day of your last period or a known conception date. Confirm with your healthcare provider.

Private on your device

Your information stays on your device and is not uploaded.

Related tools

Estimate a due date from the first day of the last menstrual period or a conception date. Optional cycle length adjusts the LMP estimate. See gestational age, trimester, countdown, and progress. Educational only—not medical advice.

How to use this tool

1. Enter the first day of your last menstrual period or conception date as prompted. 2. Adjust cycle length if that field is shown. 3. Click Calculate. 4. Review estimated due date and current gestational week. 5. Confirm with your healthcare provider—only clinical dating is definitive.

Worked example

Example: LMP 1 January with a 28-day cycle estimates a due date around early October—ultrasound dating may differ.

How it works

Enter the first day of the last menstrual period (LMP) or a conception date. For LMP, an optional cycle length adjusts Naegele’s rule (280 days from LMP on a 28-day cycle). The calculator estimates due date, gestational age, trimester, and days remaining. Results are educational estimates only and are not medical advice.

Limitations

This tool provides a general estimate for educational purposes and is not medical advice. Due dates are estimates only. Consult a qualified healthcare professional for personal guidance.

Privacy and file handling

Your data stays on your device and is not uploaded.

Accuracy & methodology

This section documents how the calculator works, what it leaves out, and when results were last reviewed. Figures are educational estimates—not professional advice—and are not labeled "current" unless tied to automatically updated reference data.

Formula source or methodology
From LMP: due date = LMP + 280 days adjusted for cycle length (default 28 days). From conception: due date = conception + 266 days. Gestational age counted from estimated LMP; trimesters at 13 and 27 weeks.
Jurisdiction
Obstetric dating conventions (general; not a country-specific clinical protocol)
Unit system
Calendar dates (ISO YYYY-MM-DD)
Rounding method
Whole days and completed weeks for gestational age
Assumptions
  • Regular cycle adjustment via user-entered cycle length (21–45 days)
  • Single fetus; spontaneous pregnancy dating conventions
  • Calendar dates without time-of-day
Known omissions
  • Not medical advice. Does not diagnose, treat, or replace clinical assessment.
  • Ultrasound dating or IVF transfer-day adjustments
  • Irregular cycles beyond the cycle-length field
  • Multiple gestation and pregnancy complications
Test cases (automated)
  • LMP 2026-01-01 with 28-day cycle → due date 2026-10-08
  • Future LMP relative to as-of date is rejected
Version & last verified

Logic version 1.0. Content and formulas last verified .

FAQ

Frequently asked questions

How is the due date calculated?

From the last menstrual period (LMP), the estimate uses 280 days for a 28-day cycle, adjusted by cycle length. From conception, it uses 266 days.

What is gestational age?

Gestational age is counted from the estimated LMP in weeks and days, and is used to determine the trimester and progress percentage.

Is this medical advice?

No. Results are educational estimates only. Confirm dates and care plans with a qualified healthcare professional.

What is this tool?

Estimates a pregnancy due date from LMP or conception date.

Are my inputs uploaded?

This tool runs in your browser. Your inputs are not uploaded to our server.

Which related tools should I use next?

Try Baby Name Generator or Childcare Cost Calculator.

Related pages

Page last reviewed: