Pregnancy Week-by-Week Tracker

Frequently Asked Questions

How is my current pregnancy week calculated?

Weeks pregnant = (today − LMP) ÷ 7, rounded down, with days as the remainder. Week 12⁺³ means 12 full weeks plus 3 days since LMP; the first trimester is 1–13⁶, second 14–27⁶, third 28–40⁺.

What size analogies does the tool use?

Common produce comparisons: week 8 raspberry (≈1.6 cm), week 12 lime (≈5.4 cm), week 20 banana (≈25 cm), week 30 cabbage (≈40 cm), week 40 small pumpkin (≈51 cm). Lengths are CRL until ≈20 weeks, then crown-heel.

Why do the weeks count from LMP, not conception?

Most people know the LMP but not the exact conception date, and ovulation varies. LMP dating adds ≈2 weeks to true embryonic age but is the global obstetric standard, which keeps screening windows (NT scan, anatomy scan, GTT) consistent.

Are the weekly milestones medical guidance?

No - they describe typical development and common symptoms. Real pregnancies vary widely. Use the week info to know what to ask about, but rely on your OB-GYN or midwife for personalized care. This tool is not medical advice.

Provided by AllCalculators.io
Free online calculators for everyday. No registration required.

Educational only. Not medical advice.

Pregnancy & Baby Disclaimer: Educational only. Not medical advice.

This calculator is for general informational and educational purposes only and is not medical advice. It does not diagnose, treat, prevent, or replace care from your OB-GYN, midwife, pediatrician, or other qualified healthcare provider. Always consult your healthcare provider for any decisions about your pregnancy, your baby, or your postpartum recovery.

JavaScript is required to use the interactive calculator above. The questions and answers below remain readable without JavaScript.

How This Calculator Works

Obstetric pregnancies are dated in completed weeks plus extra days, measured from the first day of your last menstrual period (LMP). This tool takes that date and today's date, computes how many days have elapsed, and converts to the “weeks plus days” (w d) shorthand used in clinic notes - 24w 3d means 24 completed weeks plus 3 extra days. It also reports the trimester, your estimated due date (LMP + 280 days, Naegele's rule), and the time remaining as weeks/days. A friendly fruit-or-vegetable size reference for the current week gives you the familiar “baby is the size of a ___” checkpoint that has become a tradition of pregnancy apps and books.

Formula / Method

Gestational age (days) = today − LMP. Weeks = floor(days ÷ 7); remainder = extra days. Trimesters by convention: first = weeks 0–13, second = weeks 14–27, third = weeks 28–40+. EDD = LMP + 280 days. Remaining time = EDD − today (clamped at zero past term). The size-by-week reference draws from common pregnancy-resource conventions: 4w = poppy seed, 8w = raspberry, 12w = plum, 16w = avocado, 20w = banana, 24w = ear of corn, 28w = eggplant, 32w = jicama, 36w = romaine lettuce, 40w = small pumpkin. These are illustrative analogies, not literal measurements - actual length runs from ≈ 0.4 cm at 4 weeks to ≈ 50 cm at term, and weight from < 1 g to ≈ 3.4 kg average.

Worked Example

LMP = January 1 and today = July 1: elapsed days = 181, so 181 ÷ 7 = 25 weeks 6 days, second trimester. EDD = January 1 + 280 days ≈ October 8; days to EDD = 99, so 14 weeks 1 day remaining. Current week 25 size reference = rutabaga. Two weeks later you would be 27w 6d (the last day of the second trimester); the day after, 28w 0d, you officially enter the third trimester. The first prenatal visit is usually scheduled around 8–10 weeks; the anatomy scan around 18–22 weeks; gestational diabetes screening 24–28 weeks; group B strep swab 35–37 weeks.

Common Mistakes

Counting from conception rather than LMP - obstetric weeks are LMP-based, so at the moment of a positive test (~4 weeks) the embryo is biologically only ~2 weeks old.

Treating EDD as a hard deadline - only ≈ 4–5% of babies are born on EDD; 37–42 weeks is the normal term window.

Ignoring an ultrasound-revised EDD - if a first-trimester scan moved your due date by > 7 days, use that revised LMP equivalent here, not your remembered period.

Comparing “size of a ___” benchmarks across apps - analogies vary wildly because real-world fruit sizes do; do not infer growth problems from analogy mismatches.

Skipping the “extra days” component - rounding 24w 6d down to “24 weeks” can put you in the wrong screening window if it crosses a clinical cutoff (e.g. the 28-week glucose tolerance test).

Tips & FAQ

How accurate is LMP dating? Within ~± 7 days for someone with regular cycles and a clearly remembered LMP. Irregular cycles, recent hormonal contraception, breastfeeding, and uncertain LMP all reduce accuracy - a first-trimester ultrasound is more precise. What if I don't know my LMP? Use a known conception/ovulation date or an ultrasound CRL with our IVF/Ultrasound Due Date tool. What is “full term”? ACOG defines: early term 37 0/7 to 38 6/7, full term 39 0/7 to 40 6/7, late term 41 0/7 to 41 6/7, post-term ≥ 42 0/7. Does the trimester boundary mean anything clinical? Yes - risk of miscarriage drops sharply after 12 weeks; many screening tests are sequenced by trimester; and viability with NICU support starts around 22–24 weeks. This tool is for general orientation and is not medical advice; for individual milestones, screening dates, and any concerning symptom, consult your healthcare provider.

Pregnancy Week-by-Week Tracker

Frequently Asked Questions

Related Pregnancy & Baby Calculators