How is gestational age calculated?

Gestational age is counted from the first day of your last menstrual period (LMP). The number of days since the LMP is shown as weeks plus days, and the estimated due date is the LMP plus 280 days (40 weeks), following Naegele's rule.

How accurate is this tracker?

It uses Naegele's rule, the standard method for an estimated due date, which assumes a regular 28-day cycle. Real cycles vary, and an early dating ultrasound is more accurate. Treat this as an informational estimate, not medical advice — always follow your clinician's dating.

Can I track from my due date instead of my last period?

Yes. Switch the mode to EDD and enter your due date; the tracker works backwards to find the LMP (EDD − 280 days) and then shows your current week, day and trimester.

How many weeks does a full pregnancy last?

A full-term pregnancy is about 40 weeks (280 days) from the LMP. Babies are considered full term from 37 weeks, and anything past the due date is regarded as post-term.

What week does each trimester start?

The first trimester is weeks 0–13, the second is weeks 14–27, and the third runs from week 28 to birth. The tracker labels which trimester your current week falls in.

Why count from the last period and not conception?

The LMP is a date most people can identify, whereas conception happens around two weeks later and is harder to date. Counting from the LMP is the standard clinical convention, so it matches what your provider uses.

Is my pregnancy data kept private?

Yes. The dates you enter are processed entirely in your browser using JavaScript. Nothing is stored, logged or transmitted anywhere.

What is the Pregnancy Week Tracker?

Free pregnancy week tracker. Enter the first day of your last period or your due date to see your current gestational age in weeks and days, your trimester and your estimated due date using Naegele's rule. Privacy-first — every date is calculated in your browser and nothing is uploaded. It runs free in your browser on Gera Tools, with nothing uploaded.

Pregnancy Week Tracker

Name: Pregnancy Week Tracker
Creator: Gera Tools
License: https://creativecommons.org/licenses/by/4.0/

Get one useful tool a week

Like this tool? Enter your email and we'll send you one genuinely useful Gera tool a week — plus a link to come back to this one. No spam, one-click unsubscribe any time.

Pregnancy week tracker

Find out how many weeks pregnant you are, which trimester you are in and your estimated due date — all from a single date. It is a simple way to follow your progress week by week and see how much of the pregnancy is left.

How it works

You can start from either the last period or the due date, and the tracker derives the other and your current progress:

from LMP:  EDD = LMP + 280 days (Naegele's rule)
from EDD:  LMP = EDD − 280 days
gestational age = days since LMP, shown as weeks + days
trimesters:  1st = weeks 0–13, 2nd = 14–27, 3rd = week 28 onward

It also shows the percentage complete and the days remaining until the due date.

Worked example

If today is 98 days after the LMP:

Gestational age: 14 weeks 0 days
Trimester: Second
Percentage complete: 98 ÷ 280 ≈ 35%
Days remaining: 280 − 98 = 182 days

Days since LMP	Weeks + days	Trimester
56	8w 0d	First
98	14w 0d	Second
224	32w 0d	Third

What happens each trimester

Understanding what gestational week you are in helps you track which appointments, scans, and screenings to expect.

First trimester (weeks 0–13): All major organs begin to form. Key appointments include the booking appointment (around 8–10 weeks in the UK NHS), and the dating scan / nuchal translucency scan (10–13 weeks). Blood tests for chromosomal conditions typically happen around 10–14 weeks in combined first-trimester screening.

Second trimester (weeks 14–27): Often considered the most comfortable phase — morning sickness typically eases and energy returns. The anatomy scan (also called the 20-week scan or anomaly scan) is the major milestone, typically offered between 18 and 21 weeks in the UK. Foetal movements usually become noticeable between weeks 18 and 22 for first-time pregnancies, sometimes slightly earlier in subsequent pregnancies.

Third trimester (weeks 28–40+): The focus shifts to growth monitoring, birth planning, and Group B Strep testing. Presentation (whether the baby is head-down) becomes important from around 36 weeks. Babies are considered full term from 37 weeks; babies born between 37 and 42 weeks are term. A pregnancy is considered post-term after 42 weeks.

Week-by-week tracker vs due date calculator

This tracker is designed for checking in regularly — each time you visit, it updates the current week and days remaining. The companion pregnancy due date calculator focuses on the initial calculation and milestone overview. For day-to-day tracking of weekly progress and trimester position, this tool is the simpler option.

Using your due date instead of your LMP

If your due date was set by an ultrasound scan rather than your LMP, use the “enter due date” mode. The tracker works backwards to find the implied LMP (EDD minus 280 days) and then computes your gestational age from that. If your clinician’s scan date gives a different gestational age than the LMP-based estimate, the scan date is more accurate — enter the EDD from the scan, not the one calculated from your period.

This is an informational estimate, not medical advice. Your clinician’s dating scan always takes precedence. Every date is calculated locally in your browser and nothing is uploaded.