How is the due date calculated?

This tool uses Naegele's rule: add 280 days (40 weeks) to the first day of your last menstrual period (LMP). If your cycle differs from 28 days the due date shifts by the difference — a 30-day cycle moves the EDD 2 days later, a 25-day cycle moves it 3 days earlier.

Is this calculator free?

Yes — completely free, no signup, no account, and no usage limits.

Does my data leave my device?

No. All calculations run in JavaScript inside your browser. Nothing is ever sent to a server.

Does it work on mobile?

Yes. The calculator is mobile-first and works on iPhone Safari and Android Chrome without any app installation.

What if my cycle is not 28 days?

Enter your actual average cycle length using the cycle-length field (range 21–45 days). The EDD shifts by the difference from 28 days — a 30-day cycle moves it 2 days later; a 25-day cycle moves it 3 days earlier.

What does the week-by-week milestone table show?

Key clinical milestones with calculated dates: positive pregnancy test (week 4), heartbeat scan (week 6), end of 1st trimester (week 12), anatomy ultrasound (week 20), viability (week 24), 3rd trimester start (week 28), early full term (week 37), and your EDD (week 40). Milestones already passed appear in grey.

Is the due date exact?

The estimated due date (EDD) is a statistical midpoint. Only about 5% of babies are born on their exact EDD — most births occur between weeks 37 and 42.

Calculadora de Fecha de Parto — Semana a Semana

Calcula tu fecha probable de parto desde la última regla y consulta los hitos semana a semana del embarazo. Gratis, privado, sin registro, funciona en tu navegador.

100% client-side · no upload · no signup

First day of last menstrual period (LMP)

Average cycle length (days, 21–45)

Your due date and week-by-week milestone timeline will appear here.

How to use

Enter the date of the first day of your last menstrual period (LMP).
Adjust the cycle length if your average differs from 28 days (range: 21–45 days).
Click Calculate Due Date to see your EDD and full week-by-week milestone timeline.

Related pregnancy & health tools

Ovulation Calculator — estimate your fertile window and ovulation date
Pregnancy Due Date (basic) — quick Naegele's rule EDD without milestone view
Water Intake Calculator — hydration needs increase during pregnancy
BMR Calculator — daily calorie needs rise in pregnancy
Macro Split Calculator — protein, carb, and fat targets for pregnancy nutrition

Explore by scenario

Preguntas frecuentes

How is the due date calculated?: This tool uses Naegele's rule: add 280 days (40 weeks) to the first day of your last menstrual period (LMP). If your cycle differs from 28 days the due date shifts by the difference — a 30-day cycle moves the EDD 2 days later, a 25-day cycle moves it 3 days earlier.
Is this calculator free?: Yes — completely free, no signup, no account, and no usage limits.
Does my data leave my device?: No. All calculations run in JavaScript inside your browser. Nothing is ever sent to a server.
Does it work on mobile?: Yes. The calculator is mobile-first and works on iPhone Safari and Android Chrome without any app installation.
What if my cycle is not 28 days?: Enter your actual average cycle length using the cycle-length field (range 21–45 days). The EDD shifts by the difference from 28 days — a 30-day cycle moves it 2 days later; a 25-day cycle moves it 3 days earlier.
What does the week-by-week milestone table show?: Key clinical milestones with calculated dates: positive pregnancy test (week 4), heartbeat scan (week 6), end of 1st trimester (week 12), anatomy ultrasound (week 20), viability (week 24), 3rd trimester start (week 28), early full term (week 37), and your EDD (week 40). Milestones already passed appear in grey.
Is the due date exact?: The estimated due date (EDD) is a statistical midpoint. Only about 5% of babies are born on their exact EDD — most births occur between weeks 37 and 42.

Last updated: 2026-05-20 By jarvisbox

Reportar un problema con esta herramienta