Baby growth calculator
Baby growth calculator
The change between two weighings: grams gained a day and a week, and the number of days between them — not a percentile and not a growth chart.
How this is calculated
Change = later weight - earlier weight. Grams a day = change in grams / days between the weighings; grams a week = grams a day x 7. The dates must be different and in order.
- A growth chart plots a weight against age and compares it with a reference population; this page does neither. It reports the change between two of your own readings, which is a different quantity, and two different scales can add a difference of their own — weigh on the same scale where you can.
- If the later weight is lower than the earlier one, that is a fact to raise at the next visit rather than a diagnosis, and this page will not dress it as one.
- This page is arithmetic, not antenatal care. It does not examine you or your baby, does not read a result as normal or otherwise, and does not replace an appointment. A dating scan, a growth chart and a clinician's advice take precedence over every figure here.
Two weighings and the days between them give a rate of gain. This page reports that rate; it does not plot a growth chart, compare a baby with a reference population or call a figure normal.
A change, not a percentile
The arithmetic is a subtraction and a division: later weight less earlier weight, then divided by the days between. Grams a day and grams a week are the same change stated in two units, and both are printed so a reader can check the conversion.
A growth chart is a different instrument. It plots a weight against age and compares it with a reference population, and the percentiles on it belong to the chart and the clinician reading it. This page cannot see the chart, the age or the measurement technique, so it reports only what the two numbers imply.
Questions readers ask
What if the weight went down?
The page reports a negative change and says to raise it at the next visit. It does not diagnose a cause. A lower later reading can come from a different scale, a different time of day or a real change, and only a clinician can tell which.
Which scale should I use?
The same one for both readings where possible. Two scales can differ by more than a day’s gain, which would show up in the rate as if it were growth.
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