Pregnancy Due Date Calculator
Estimate the due date, current week of pregnancy and each trimester from your last period.
Inputs
Formula
- Due date = LMP + 280 days, adjusted for cycles longer or shorter than 28 days
Naegele's rule counts 40 weeks from the first day of the last period. If your cycle is not 28 days, ovulation shifts and so does the due date. Only about 4% of babies arrive on the exact date — anywhere from 37 to 42 weeks is full term.
Step-by-step calculation
- 1
Naegele's rule
LMP + 280 days
Aug 9, 1970
Warnings
- This is an estimate for planning only. An ultrasound dating scan is far more accurate.
Frequently asked questions
What does the Pregnancy Due Date Calculator do?
Estimate the due date, current week of pregnancy and each trimester from your last period. The Pregnancy Due Date Calculator on OneCalcApp returns the result instantly as you type, together with the formula and the substituted values.
How do I use the Pregnancy Due Date Calculator?
Enter your values in the input fields, choose the relevant units or options, and the Pregnancy Due Date Calculator recalculates automatically. You can copy, print or export the result.
Is the Pregnancy Due Date Calculator free to use?
Yes. The Pregnancy Due Date Calculator is completely free, needs no sign-up and has no usage limit on OneCalcApp.
How accurate is the Pregnancy Due Date Calculator?
It uses the standard formula Due date = LMP + 280 days, adjusted for cycles longer or shorter than 28 days and full double-precision arithmetic, so results match a manual calculation to the displayed number of digits.
Does the Pregnancy Due Date Calculator work on mobile and offline?
Yes. The Pregnancy Due Date Calculator runs entirely in your browser on phones, tablets and desktops, and your inputs never leave your device.
Where can I find related tools?
OneCalcApp hosts 300+ calculators and converters, including the full Health collection. Related tools are linked at the bottom of every page.
Related calculators
Keep going with more health tools.
Ovulation Calculator
Find your likely ovulation day and fertile window from your last period and cycle length.
Age Calculator
Calculate exact age in years, months and days from a date of birth, plus total weeks, days, hours and the next birthday countdown.
Date Difference Calculator
Find the number of days, weeks, months and years between two dates, including business days excluding weekends.
BMI Calculator
Calculate Body Mass Index with the WHO classification, healthy weight range and BMI Prime, in metric or imperial units.
Calorie Calculator (TDEE & Macros)
Estimate your daily calorie needs (BMR and TDEE) with the Mifflin-St Jeor equation, adjust for your goal, and get a protein, carb and fat macro split. Everything is calculated in your browser.
BMR Calculator
Find your basal metabolic rate — the calories your body burns at complete rest.