Pregnancy & Baby Calculators

How to use these 6 calculators

Choose a calculator above, enter the relevant dates, and click Calculate →. Results appear directly below the input fields. Use Copy Direct Link ↗ to share a link that reopens this same tab, or follow the related-tool links to switch calculators instantly.

Pregnancy dating and due dates

The conventional due-date formula starts 280 days after the last menstrual period. If conception date is known, an estimate is approximately 266 days later. These dates can differ from a clinically established due date, particularly when periods are irregular or an early ultrasound gives different measurements.

Baby age, adjusted age and corrected age

Chronological age counts from the actual birth date. Adjusted age and corrected age are two names for the same prematurity adjustment, based on how many weeks early a baby was born. They are educational date calculations, not developmental diagnoses.

Frequently asked questions

How is a pregnancy due date estimated?

Common date-based methods use 280 days from the first day of the last menstrual period or approximately 266 days from a known conception date. A clinician may confirm or revise the estimate based on early ultrasound.

Can a 28-day cycle affect the due date calculation?

Yes. The last-period method assumes a 28-day cycle. Changing the average cycle length can shift an estimate, although individual ovulation timing varies.

What is gestational age?

Gestational age generally counts weeks and days from the last menstrual period or from a clinician-established estimated due date.

How accurate is the conception calculator?

It is only an approximation for naturally conceived pregnancies because ovulation and fertilization dates can vary.

How are baby age and adjusted age different?

Chronological age counts from birth. Adjusted or corrected age subtracts how early a premature baby was born when interpreting early development.

Is adjusted age different from corrected age?

No. The terms are used interchangeably. These two calculator tabs offer different input methods for the same underlying calculation.

What happens if corrected age is negative?

The tool shows how many days remain until the original estimated due date instead of presenting a negative age as a developmental assessment.

Should I use these results for medical decisions?

No. Date calculators are educational aids and cannot replace prenatal dating, growth assessment, or advice from a qualified clinician.

Medical references

ACOG: Methods for Estimating the Due Date · NHS: Due Date Calculator · AAP: Preemie Milestones & Adjusted Age

Important: These are educational date estimates, not a diagnosis, pregnancy confirmation or substitute for medical advice. For established pregnancies, rely on the due date recorded by your prenatal care team. For a premature baby's development, discuss interpretation of corrected age with the pediatric care team.