About FROGS
FROGS is a free fetal growth calculator for clinicians and researchers. It turns a birthweight and gestational age into growth centiles, z-scores and charts — using growth standards calibrated to the local population rather than a one-size-fits-all global reference.
How it works
Three steps from measurement to chart — click through to see each one.
Birthweight (or estimated fetal weight) and gestational age — typed directly, or worked out from the scan date and due date.
Birthweight (or estimated fetal weight) and gestational age — typed directly, or worked out from the scan date and due date.
Why region-specific?
Growth references differ between populations — the same weight can sit on very different centiles. A standard tuned to the regional population gives a fairer read on whether a baby is growing as expected.
- Reduces both missed growth restriction and over-flagging of healthy babies
- ±10% centile bands accompany every estimate, keeping measurement uncertainty visible
- Calibrated to local birthweight data, not a one-size-fits-all global curve
A decision-support tool
FROGS supports clinical assessment — it does not replace it. Results should always be interpreted alongside the full clinical picture by a qualified health professional.