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Baby size by week.

The whole chart on one page — and the actual number beside every comparison.

Most size charts hand you a piece of fruit and nothing else. This one prints the measurement in centimetres and inches next to the drawing, because a comparison you cannot check is a comparison you have to take on faith.

How these are measured

Up to week 19 a baby is measured crown to rump — the top of the head to the bottom of the torso — because the legs are curled and cannot be measured reliably. From week 20 the measurement is head to heel, which is why the numbers jump between those two rows. It is a change of ruler, not a growth spurt.

Weeks one to three are dated from before conception and carry no size at all. Week four is the implantation week, described in the clinical source as approximately the size of a pinhead with no figure given, so none is printed here.

First trimester · Weeks 1–13
WeekDrawn asLengthMeasured
Week 1A seed, heldNo size stated—
Week 2The seed in soilNo size stated—
Week 3First root, unseenNo size stated—
Week 4Baby's-breath floretNo size stated—
Week 5Lilac floret0.2 cm (0.1 in)Crown to rump
Week 6Forget-me-not0.5 cm (0.2 in)Crown to rump
Week 7Lily-of-the-valley bell1 cm (0.4 in)Crown to rump
Week 8Violet1.6 cm (0.6 in)Crown to rump
Week 9Chamomile bloom2.3 cm (0.9 in)Crown to rump
Week 10Cherry blossom3.1 cm (1.2 in)Crown to rump
Week 11Crocus4.1 cm (1.6 in)Crown to rump
Week 12Daffodil5.4 cm (2.1 in)Crown to rump
Week 13Tulip bloom6.7 cm (2.6 in)Crown to rump

Read the first trimester →

Second trimester · Weeks 14–27
WeekDrawn asLengthMeasured
Week 14Magnolia bloom8.7 cm (3.4 in)Crown to rump
Week 15Pansy10.1 cm (4.0 in)Crown to rump
Week 16Gerbera daisy11.6 cm (4.6 in)Crown to rump
Week 17Bearded iris13 cm (5.1 in)Crown to rump
Week 18Water lily14.2 cm (5.6 in)Crown to rump
Week 19Hibiscus15.3 cm (6.0 in)Crown to rump
Week 20Sweet pea, full stem25.6 cm (10.1 in)Head to heel
Week 21Anemone27.4 cm (10.8 in)Head to heel
Week 22Morning glory29 cm (11.4 in)Head to heel
Week 23Freesia30.6 cm (12.0 in)Head to heel
Week 24Marigold32.2 cm (12.7 in)Head to heel
Week 25Begonia33.7 cm (13.3 in)Head to heel
Week 26Lavender sprig35.1 cm (13.8 in)Head to heel
Week 27Calla lily36.6 cm (14.4 in)Head to heel

Read the second trimester →

Third trimester · Weeks 28–40
WeekDrawn asLengthMeasured
Week 28Iceland poppy37.6 cm (14.8 in)Head to heel
Week 29Cosmos39.2 cm (15.4 in)Head to heel
Week 30Zinnia40.5 cm (15.9 in)Head to heel
Week 31Black-eyed Susan41.8 cm (16.5 in)Head to heel
Week 32Aster43 cm (16.9 in)Head to heel
Week 33Hydrangea stem43.7 cm (17.2 in)Head to heel
Week 34Snapdragon45 cm (17.7 in)Head to heel
Week 35Dahlia, full stem46.2 cm (18.2 in)Head to heel
Week 36Peony, full stem47.4 cm (18.7 in)Head to heel
Week 37Orchid spike48.6 cm (19.1 in)Head to heel
Week 38Stargazer lily stem49.2 cm (19.4 in)Head to heel
Week 39Sunflower, cut stem50.1 cm (19.7 in)Head to heel
Week 40Long-stemmed rose51.2 cm (20.2 in)Head to heel

Read the third trimester →

Why these are averages

Every figure here is a typical measurement for that week. Real babies vary considerably, and a baby measuring above or below one of these numbers is usually just a baby. What matters clinically is the pattern of growth over time, which your midwife or doctor is tracking, and not a single row of a chart on the internet.

If a scan has given you a measurement that worries you, the person to ask is the one who took it.

Where this came from
  1. ACOG: fetal growth
  2. NHS
  3. NHS
  4. NHS
  5. NHS
  6. NHS

See it at actual size

Zohra draws each of these flowers at the real measurement on your phone, so the number stops being abstract. The true-scale stage shows the whole story in one place.

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