How many months is 20 weeks pregnant?

20 weeks is roughly 4½ months. Months are an awkward unit in pregnancy because they do not divide evenly into weeks — a calendar month averages about 4.3 weeks, which is why 40 weeks works out a little over nine months rather than ten. Appointments and scans are always booked in weeks, so weeks are the figure worth carrying.

How big is a baby at 20 weeks?

The NHS publishes around 25.6 cm long, from head to heel for week 20. Rather than one fruit, that length is offered here against eight rulers, each object carrying its own measurement: the giant Toblerone from duty-free (26 cm end to end), a rainbow lorikeet (26 cm beak to tail), a Bop It (26 cm end to end), a basketball (24.3 cm across), and four more. Published lengths are averages across many babies, not a measurement of any particular one, and a scan estimate that differs is a normal thing rather than a finding.

What trimester is 20 weeks?

Week 20 is in the second trimester, on the commonly published split of weeks 1–12, 13–26 and 27 onward. The boundaries are conventions for talking about pregnancy rather than biological switches — nothing changes overnight at week 13 or week 27.

20 weeks pregnant

What happens at 20 weeks pregnant?

At 20 weeks a baby is around 25.6 cm long, from head to heel, about the size of the giant Toblerone from duty-free. That is roughly 4½ months, in the second trimester, with about 20 weeks to go until 40.

Published length

25.6 cm long, from head to heel

In months

Roughly 4½ months

Trimester

second · 20 weeks to go

What is developing at 20 weeks

Halfway. The anomaly scan usually happens between 18 and 21 weeks, checking growth, the position of the placenta and how the organs are developing. The baby is now producing meconium — the dark first bowel movement — and swallowing amniotic fluid regularly.

The size comparison above is the giant Toblerone from duty-free, which measures 26 cm end to end. Every comparison on this site is a real object with a real measurement, checked against the published length. The same week is drawn in seven other sets below, from Australian animals to fast food, if this one means nothing to you.

20 weeks, in eight rulers

Every other pregnancy tool measures a baby in fruit. This one offers eight sets to choose from, and each object below carries its real measurement, checked against the 25.6 cm the NHS publishes for week 20. Pick whichever ruler you actually have a feel for. Why not fruit.

Sweet treats
the giant Toblerone from duty-free
26 cm end to end
Australian animals
a rainbow lorikeet
26 cm beak to tail
The 90s
a Bop It
26 cm end to end
Sport
a basketball
24.3 cm across
Things you already own
a dinner plate
26 cm across
Gaming
a Nintendo Switch, Joy-Cons on
24.2 cm side to side
Fast food
a slice of large pizza
25 cm tip to crust
Toys
a small teddy bear
25 cm ears to feet

Your dates, from 20 weeks

Set to someone who is exactly 20 weeks today, so the due date below is the one that implies. Change the date to your own and everything follows from it — nothing is saved unless you do.

How far along am I?

Your due date

Do not know your due date yet? The due date calculator estimates one from your last period. A dating ultrasound is more accurate than any calendar method — if your pregnancy care team has given you a date, use theirs.

Questions about 20 weeks

How many months is 20 weeks pregnant?: 20 weeks is roughly 4½ months. Months are an awkward unit in pregnancy because they do not divide evenly into weeks — a calendar month averages about 4.3 weeks, which is why 40 weeks works out a little over nine months rather than ten. Appointments and scans are always booked in weeks, so weeks are the figure worth carrying.
How big is a baby at 20 weeks?: The NHS publishes around 25.6 cm long, from head to heel for week 20. Rather than one fruit, that length is offered here against eight rulers, each object carrying its own measurement: the giant Toblerone from duty-free (26 cm end to end), a rainbow lorikeet (26 cm beak to tail), a Bop It (26 cm end to end), a basketball (24.3 cm across), and four more. Published lengths are averages across many babies, not a measurement of any particular one, and a scan estimate that differs is a normal thing rather than a finding.
What trimester is 20 weeks?: Week 20 is in the second trimester, on the commonly published split of weeks 1–12, 13–26 and 27 onward. The boundaries are conventions for talking about pregnancy rather than biological switches — nothing changes overnight at week 13 or week 27.

Where these numbers come from

NHS — Week-by-week guide to pregnancy — The published length of a baby at each week of pregnancy — measured head to bottom until week 20 and head to heel from week 20 — and what is developing at that stage.
Pregnancy, Birth and Baby — Pregnancy week by week — The Australian Government health service’s week-by-week account of how a pregnancy is counted and what develops at each stage.

General information only, not medical advice. BubSync is not a medical device: these tools do not diagnose, treat or monitor any condition, and using one does not create a clinical relationship. Every baby is different, and these are published ranges rather than targets to hit — they may not apply to your baby, particularly if they were born preterm, are small or large for their age, or have a medical condition. Never delay or disregard advice from a health professional because of something a calculator here showed you. If you are worried about feeding, sleep, weight or wet nappies, contact your child health nurse, midwife or GP — and if your baby seems unwell, floppy, or is difficult to rouse, seek urgent medical care now (000 in Australia).

Written by the BubSync editorial team. Not yet reviewed by an independent clinician. The editorial policy says who writes these pages and how their figures are sourced. Read how we write and check these pages.

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