LMP Apr 1, 2026, 28 day cycle
- Gestational age today
- 17w 0d
- Estimated conception
- Apr 15, 2026
- Trimester
- Second trimester
Due Date Calculator
Use this free due date calculator to estimate expected delivery date from the first day of the last menstrual period and usual cycle length, with conception timing and clinical-dating limits.
Estimate, not diagnosisFormula notesExample inputsTab-only history
Formula steps
- Start with the first day of the last menstrual period.
- Add 280 days, adjusting for cycle length compared with a 28-day cycle.
- Estimate conception near ovulation, about 14 days before the next period.
Examples
Recent answers
Recent due date estimates will appear here.
A due date is an estimate, not a guarantee of delivery timing.
Inputs and recent answers stay in this browser tab and are not sent to a server.
How to use the Due Date Calculator
- Enter the requested measurements, dates, lab values, or workout details.
- Check that the units and formula assumptions match what the tool is asking for.
- Press the calculate button to see the answer, supporting metrics, and formula steps.
- Read the estimate with the health disclaimer in mind, then copy the result if you need it for notes.
What people use it for
Estimate an expected due date from the first day of the last menstrual period.
Adjust the due-date estimate for shorter or longer usual cycle length.
See estimated conception timing, gestational age today, and trimester context.
Use a simple planning date before clinical dating is confirmed.
Quick examples
LMP Apr 1, 2026
28-day cycle: Apr 1 + 280 daysEstimated due Jan 6, 2027; conception around Apr 15
LMP Feb 14, 2026
32-day cycle: add 284 daysEstimated due Nov 25, 2026; conception around Mar 4
LMP May 5, 2026
26-day cycle: add 278 daysEstimated due Feb 7, 2027; conception around May 17
LMP Jun 10, 2026
35-day cycle: add 287 daysEstimated due Mar 24, 2027; conception around Jul 1
Need the guide or a nearby tool?
Need a slower walkthrough, a related calculator, or the full library? These links keep you close to the task you started.
- How to use the Due Date CalculatorSee slower examples, input meanings, formula notes, result limits, and mistakes to avoid.
- Health & FitnessBrowse related calculators and utilities in the same category.
- Calculator and utility guidesFind more guides that use real tool inputs and example numbers.
- All free toolsSearch every live tool, converter, calculator, AI helper, and browser utility.
Frequently asked questions
Plain-language answers about when to use the estimate, what the formula means, what it cannot decide for you, and how privacy works.
When should I use the Due Date Calculator?
Use it for simple educational checks, trend tracking, or planning tasks like these: Estimate an expected due date from the first day of the last menstrual period. Adjust the due-date estimate for shorter or longer usual cycle length. It can help you understand a number, but it cannot explain your whole health situation.
What do the main Due Date Calculator inputs mean?
Enter the first day of the last menstrual period, not the last day of bleeding. Cycle length means the usual number of days from one period start to the next. Use 28 only if that is close for you, and use clinician, ultrasound, or IVF dating if that has already been assigned.
What is the Due Date Calculator doing with my inputs?
In plain language: The calculator uses Naegele-style dating: due date = first day of LMP + 280 days + (cycle length - 28 days). It estimates conception near LMP + cycle length - 14 days and counts gestational age from LMP to today. Read the result together with the notes on the page, because health and fitness numbers often need personal context.
How should I read the Due Date Calculator result?
Read the due date as an estimated delivery date from LMP calendar math, not a guarantee of when birth will happen. The gestational-age, conception, and trimester lines are planning references only. An early ultrasound, IVF date, or clinician review can override the calculator.
Why does the due date calculator add 280 days?
A common LMP-based pregnancy estimate counts about 280 days, or 40 weeks, from the first day of the last menstrual period. That is gestational-age dating, so it starts before estimated conception.
Why does cycle length change the due date?
Cycle length shifts the estimated ovulation timing. A 32-day cycle moves the estimate about four days later than a 28-day cycle, while a 26-day cycle moves it about two days earlier. Irregular cycles make calendar dating less reliable.
Should I enter the first or last day of my period?
Enter the first day bleeding started for the last menstrual period. The formula is built around the period start date, not the last bleeding day, ovulation day, positive test date, or appointment date.
Is the estimated due date guaranteed?
No. It is a planning estimate. Many healthy pregnancies deliver before or after the due date, and medical details can change how your care team interprets timing.
When should ultrasound, IVF, or clinician dating override this calculator?
Use the official date from your care team when one has been assigned, especially after early ultrasound, IVF transfer dating, uncertain LMP, irregular cycles, multiples, bleeding that may not have been a true period, or medical concerns.
Can this prove the exact conception date or parentage?
No. The conception line is an estimate near ovulation, not proof of an exact day, intercourse date, or parentage. Ovulation shifts, sperm survival, fertilization timing, and dating uncertainty all matter.
Can I use this as medical advice?
This calculator gives an educational pregnancy-date estimate only. It is not prenatal care, ultrasound dating, IVF dating, labor guidance, emergency advice, paternity proof, or clinician advice. Use the calculator as a learning tool, then ask a qualified professional about decisions that affect care, pregnancy, medication, nutrition, or safety.
What should I double-check before trusting the result?
Check the units, date, and personal details before reading the answer. For example, pounds and kilograms, inches and centimeters, or a wrong activity level can change the result quickly. If the number feels surprising, rerun it slowly and compare it with the examples.
Does the site save my health inputs?
No. The calculator runs in your browser tab. Recent answers stay only on the page while you use it, and they are not sent to a server.