Quick start
- Open the Due Date Calculator.
- Enter the first day of the last menstrual period.
- Use the first example, "LMP Apr 1: 28-day cycle", if you want to see a filled-out calculation before entering your own values.
- Calculate, read the formula line, then copy the result only after the units and assumptions look right.
Best uses
Start here if one of these sounds like your job. The examples below show which inputs matter most.
- Estimate a due date from last menstrual period.
- Adjust the estimate for shorter or longer cycles.
- Find estimated conception date alongside due date.
- Use as a planning reference before clinical confirmation.
What this calculator is for
The Due Date Calculator focuses on expected delivery date from the first day of the last menstrual period and usual cycle length.
Use it when you want to: Estimate a due date from last menstrual period. Adjust the estimate for shorter or longer cycles.
What to enter
Good answers start with clean inputs. Before calculating, check the labels, units, and dates so the tool is solving the same problem you actually have.
- Enter the first day of the last menstrual period.
- Set the usual cycle length if it differs from 28 days.
- Use the result as a planning date until clinical dating is confirmed.
Example walkthrough
Try the calculator example: LMP Apr 1: 28-day cycle. The example result is Estimated due date Jan 6, 2027.
- With Apr 1 as LMP and a 28-day cycle, the calculator adds 280 days.
- A longer cycle moves estimated ovulation later, so the date can shift later.
Formula and steps
In plain language: The calculator uses Naegele-style dating: LMP plus 280 days, adjusted by the difference from a 28-day cycle. Read the result together with the notes on the page, because health and fitness numbers often need personal context.
Read the formula note when you need to understand where the number came from, especially before comparing results over time.
How to read the answer
Due dates are estimates. Many healthy pregnancies deliver before or after the estimated date.
- A due date is an estimate; many healthy pregnancies deliver before or after it.
- The conception estimate is backward math from the due date, not a confirmed event date.
Common mistakes to avoid
Most bad results come from a small input mistake or from using a rough estimate for a decision it cannot safely answer.
- Do not enter ovulation date into an LMP field.
- Do not treat the due date as an appointment guarantee.
- Do not ignore clinician updates after ultrasound.
What to try next
A related health tool can help check the same topic from another angle, but one number should not replace proper care.
- Use Pregnancy Calculator for gestational age and trimester too.
- Use Pregnancy Conception Calculator to work backward from a due date.
Sources and safety notes
This guide uses public-health, clinical, or peer-reviewed references where the calculator needs a specific formula or interpretation boundary.
Source links are provided for transparency, but they do not turn the calculator into medical advice or a replacement for professional care.
Worked examples for Due Date Calculator
Estimated due date Jan 6, 2027
Cycle-adjusted estimate
Cycle-adjusted estimate
FAQ in plain language
When should I use the Due Date Calculator?
Use it for simple educational checks, trend tracking, or planning tasks like these: Estimate a due date from last menstrual period. Adjust the estimate for shorter or longer cycles. 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 body, activity, date, or lab values exactly in the units shown on the page. Height, weight, age, sex, time, and activity level can change health estimates a lot, so treat each label like a rule instead of a suggestion. If you are unsure which option fits, choose the closest honest match and read the result as a rough estimate.
What is the Due Date Calculator doing with my inputs?
In plain language: The calculator uses Naegele-style dating: LMP plus 280 days, adjusted by the difference from a 28-day cycle. 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?
Use the result as a learning number, not a final answer about your body or health. The supporting lines can show categories, ranges, calories, dates, or targets, but those numbers still need context like age, medical history, pregnancy status, training level, and advice from a qualified professional.
Can I use this as medical advice?
No. This page provides an educational estimate only. Talk with a qualified health professional before making medical, pregnancy, nutrition, medication, or safety decisions. 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.
Related tools
- Pregnancy Calculator Estimate due date, pregnancy week, conception timing, and trimester from LMP.
- Pregnancy Conception Calculator Estimate conception date, window, and LMP from a due date.
- Ovulation Calculator Estimate ovulation date and fertile window from cycle details.
Keep exploring
If this guide is close but not exact, these links keep you near the same kind of problem.
- Health & Fitness Browse the full category for related tools that help with the same job.
- All free tools Search the complete Access Free Tools library by task, category, or tool name.
- All calculator and utility guides Find more plain-language examples, formulas, mistakes, and result explanations.
- Free calculator resources Start here when you are not sure which calculator page fits.
Privacy and copying results
Recent answers stay visible only while you work in the current browser tab. They are not sent to a server.
Use Copy answer when you want to save the inputs and result in notes, homework, a message, or a project list. Check the units, labels, and limits before copying.