Does my fundal height match my weeks?

Fundal height is the distance in centimetres from the top of your pubic bone to the top of your uterus, measured with a tape measure at prenatal visits from around 24 weeks. It's a quick screening check: from about 24 to 38 weeks, the centimetre reading should roughly match your week count, give or take about 2 cm — so at 30 weeks you'd expect somewhere near 28–32 cm. If the number tracks with your dates, it's a reassuring sign that growth and fluid are in a typical range. If it's well off, or it changes a lot between visits, your provider looks closer, usually with an ultrasound. It's a first-pass screen, not a measurement of the baby itself.

Not on its own. A single fundal height that's a couple of centimetres off is common and usually means nothing — the measurement is genuinely rough, and the tape, the examiner, your body, a full bladder, and the baby's position all move it. Even a bigger gap has plenty of harmless explanations: your dates may simply be off, the baby may be lying in a way that measures short or long, or there may be a bit more or less amniotic fluid than average. What a well-off reading does is earn a closer look — typically an ultrasound, which measures the baby directly and settles the question. So treat an off result here as a reason to ask, not a reason to panic.

Measuring ahead (large-for-dates) means the fundal height is more centimetres than your weeks by more than the rough tolerance — the belly is measuring bigger than the calendar suggests. Measuring behind (small-for-dates) means it's fewer centimetres than your weeks. Neither is a diagnosis. Measuring ahead can come from twins, extra amniotic fluid, fibroids, dates that are earlier than thought, or simply a bigger baby; measuring behind can come from the baby's position, less fluid, dates that are later than thought, your body size, or a baby that's genuinely growing on the smaller side. Only an ultrasound, read by your provider, can tell which of those it is — the tape measure can't.

Before about 24 weeks the uterus is still low in the pelvis, so there isn't a reliable fundus to measure to, and the tidy centimetres-equal-weeks relationship simply hasn't kicked in yet. After about 38 weeks it drifts the other way: as the baby's head settles down into the pelvis in the final weeks (called lightening or dropping), the top of the uterus can move down, so the fundal height can plateau or even fall a little while the baby keeps growing. That's normal near term and doesn't mean anything is shrinking. Because the rule only holds in that middle stretch, this tool tells you when your week count is outside the window rather than pretending to interpret it.

No — they're completely different measurements, which is why we keep them as separate tools. Fundal height is a tape measure across the outside of your belly: quick, free, and rough, and it screens the whole picture (baby, fluid, and position together) against your dates. An estimated fetal weight (EFW) comes from an ultrasound measuring the baby's head, abdomen, and femur and running them through a formula — it estimates the baby's weight specifically, and it's far more precise, though it still carries its own margin. If your fundal height looks off, an ultrasound and its EFW are usually the next step. To go the other way, our fetal weight calculator turns your scan's measurements into an estimated weight.

Yes. This calculator runs entirely in your browser: the numbers you type are compared on your own device and are never sent to a server, stored, or shared — close the tab and they're gone. We treat pregnancy data as sensitive by design, so there's no account and nothing to delete. The result is general educational information based on a standard screening rule of thumb; it isn't medical advice or a diagnosis, and it can't replace the provider who measures you or the ultrasound that settles any question about growth.