Praktické

Kalkulačka tehotenstva

Pregnancy Calculator

First day of last period

What is Pregnancy Calculator?

▾

A pregnancy calculator estimates your due date, current gestational age, and trimester based on your last menstrual period (LMP) or conception date. Pregnancy lasts approximately 40 weeks (280 days) from the LMP, though normal term is considered 37–42 weeks.

Calkulon makes complex calculations simple — built for students and everyday problem-solvers.

How to Pregnancy Calculator

▾

1Identify the first day of your last menstrual period (LMP)
2Add 280 days (40 weeks) to get the estimated due date (Naegele's Rule)
3Calculate gestational age: today − LMP in weeks and days
4Determine trimester: weeks 1–12 (first), 13–26 (second), 27–40 (third)
5If using conception date, subtract 14 days to estimate LMP

Worked Examples

▾

Example 1

Given:LMP: January 1

Výsledok:Due date: October 8

Add 280 days to LMP

Example 2

Given:Conception: January 15

Výsledok:Due date: October 22

Conception = LMP + 14 days

Special Cases

▾

Ultrasound dating

An early ultrasound (8–14 weeks) gives the most accurate gestational age. If it differs from LMP by more than 7 days, the ultrasound date is used for clinical management.

Premature vs post-term

Births before 37 weeks are premature; after 42 weeks are post-term. Full term is 39–40 weeks. Gestational age at birth is one of the strongest predictors of neonatal outcomes.

Pregnancy Trimesters

▾

Trimester	Weeks	Key Development
First	1–12	Major organs form; miscarriage risk highest
Second	13–26	Movement felt; anatomy scan at week 20
Third	27–40	Rapid growth; lung maturation; birth
Full term	37–40	Baby ready for birth
Post-term	42+	Induction often recommended

💡

Pro Tip

The first trimester is the most critical for fetal development. Folic acid supplementation (400–800 mcg/day) before and during early pregnancy significantly reduces neural tube defect risk.

⭐

Did you know?

Only about 4% of babies are born exactly on their due date. Most births occur within 2 weeks before or after.

References

Len na informačné účely. Tento nástroj nenahrádza odborné lekárske poradenstvo, diagnózu ani liečbu. Vždy sa poraďte s kvalifikovaným zdravotníckym odborníkom.

Deep Dive

Read the full guide on how to use this calculator effectively

Čítať viac →

Môžete tiež potrebovať

→

BMI Calculator for Women

→

Body Fat Calculator

→

BMR Calculator

Formula-verified for precision

Reviewed October 2026

Our methodology

Ratings & comments

…

Získajte týždenné matematické tipy

Pridajte sa k 12 000+ odberateľom, ktorí každý týždeň dostávajú tipy na kalkulačku.

🔒

100% zadarmo

Nikdy bez registrácie

✓

Presné

Overené vzorce

⚡

Okamžité

Výsledky počas písania

📱

Vhodné pre mobily

Všetky zariadenia