Newborn daily weight gain calculator (first month)
Enter the measurements at birth, the weight at the discharge check-up and today's measurements. You get the average daily weight gain, the expected weight, the percentage of expected weight and the nutritional status against the WHO growth standards.
For: Term newborns, from birth to 31 days of life. Free, no sign-up. Everything is worked out in your browser and nothing is stored.
How daily weight gain is worked out
Age is counted in days between the date of birth and today's date, and the calculator only assesses up to 31 days of life. Weights are entered in grams; length and head circumference in centimetres.
| Result | Calculation |
|---|---|
| Average daily gain | (current weight − weight at discharge) / days of life |
| Expected daily gain | 40 g/day for boys and 33 g/day for girls |
| Expected gain since discharge | expected daily gain × days since the discharge check-up (minimum 1) |
| Total expected weight | birth weight + expected daily gain × days of life |
| Percentage of expected weight | current weight × 100 / total expected weight |
| Difference in length and head circumference | current measurement − measurement at birth |
The average daily gain starts from the weight at the discharge check-up, but is divided by all the days of life, not only by the days since discharge.
Nutritional status and growth
The calculator also assesses the current weight (rounded to 0.1 kg) against the WHO growth standards for the age in months, which in the first month is 0 or 1: one month is counted once more than 15 days have passed, with 30-day months. SD: standard deviations.
| Weight for age | Nutritional status |
|---|---|
| Below −2 SD | Undernutrition by weight for age |
| From −2 SD and below −1 SD | At risk of undernutrition |
| From −1 SD and below +1 SD | Normal by weight for age |
| +1 SD or above | Normal * (outside the standard, use professional judgement) |
If weight for length (lying down, with the length in whole centimetres) is between +1 and +2 SD, the nutritional status becomes overweight; at +2 SD or above, obesity. Growth is reported as stunted growth when length for age is below −2 SD and as normal growth in every other case.
PDF report
With the result, a «Download report» button appears: a PDF built in your browser with the data entered, the comparison table of birth, discharge and today's check-up, the weight gain calculation with the percentage of expected weight, the WHO row for that age and the source. You can add an optional reference for your own records, which only goes into that PDF: no name or ID number is asked for and nothing is sent or stored. This calculator has no charts, just as on the old site.
Frequently asked questions
How many grams a day should a newborn gain?
This calculator uses an expected gain of 40 grams a day for boys and 33 grams a day for girls during the first month of life, and compares the calculated average gain and the current weight against that.
What age does it cover?
Term newborns during the first month: from birth to 31 days of life, counted between the date of birth and today's date. Beyond that it shows the message «Age limit exceeded».
How is the average daily weight gain calculated?
The weight at the discharge check-up is subtracted from the current weight and the result is divided by the days of life (from birth to today's date), to two decimal places. For example, 3,900 g today, 3,180 g at discharge and 18 days of life give (3,900 − 3,180) / 18 = 40.00 g/day.
What is the percentage of expected weight?
It is the current weight as a percentage of the total expected weight. The expected weight is the birth weight plus the expected daily gain for that sex multiplied by the days of life. A figure of 100 % means the current weight matches the expected one.
What unit is the weight entered in?
In grams, without thousands separators (3350, for example). If any weight is below 100, the calculator assumes it was written in kilograms and asks for grams. Length and head circumference are in centimetres and accept a decimal comma.
Can I download a report?
Yes. When there is a result, a «Download report» button appears that builds a PDF in your browser with the data entered, the comparison table of birth, discharge and today's check-up, the weight gain calculation, the WHO row used for the classification and the source. Nothing is sent or stored. You can type an optional reference (a case number, for instance) that only goes into that PDF; do not enter names or ID numbers.
Is the data I enter stored?
No. The child's name is not asked for, everything is worked out in your browser and no data is sent or stored. The PDF report is also generated in your browser.
Source
Expected gain used by the calculator: 40 g/day for boys and 33 g/day for girls. Nutritional status and growth: WHO child growth standards (weight for age, weight for length and length for age).
A support tool for health professionals. It does not replace clinical assessment or the technical standard in force.