Baby size by week
See how big your baby is this week, compared to a fruit, with length and weight.
We picked your week from the due date you saved on this phone.
How big is my baby this week?
Baby grows from the size of a poppy seed at 4 weeks to about the size of a small pumpkin at 40 weeks. That's around 51 cm (20 inches) long and 3.5 kg (7 lb 11 oz) at birth, on average. Pick any week above, or tap a week below.
Every week, 4 to 40
- Week 4
- Week 5
- Week 6
- Week 7
- Week 8
- Week 9
- Week 10
- Week 11
- Week 12
- Week 13
- Week 14
- Week 15
- Week 16
- Week 17
- Week 18
- Week 19
- Week 20
- Week 21
- Week 22
- Week 23
- Week 24
- Week 25
- Week 26
- Week 27
- Week 28
- Week 29
- Week 30
- Week 31
- Week 32
- Week 33
- Week 34
- Week 35
- Week 36
- Week 37
- Week 38
- Week 39
- Week 40
How we calculate this
Sizes are rounded averages from published fetal growth tables. Until week 19, babies are measured from the top of the head to the bottom (crown to rump), because their legs are curled up. From week 20, they are measured from head to heel. Fruit comparisons are a fun guide, not a measurement. Every baby grows at their own pace. Your ultrasound is the only real measurement of your baby.
Questions moms ask
Why does the length jump at 20 weeks?
Before 20 weeks, babies are measured from head to bottom. From 20 weeks, they are measured from head to heel, so the number jumps.
My baby is measuring bigger or smaller. Is that bad?
Not always. Babies grow at different speeds. Your doctor or midwife will check baby's growth at your visits and tell you if anything needs a closer look.
How big is a baby at birth?
On average, about 51 cm (20 inches) long and about 3.5 kg (7 lb 11 oz). Healthy babies can be quite a bit bigger or smaller.
Related tools
This tool gives an estimate, not medical advice. Every pregnancy and every baby is different. If you're worried about anything, talk to your doctor or midwife.