Newborn Weight Gain
Newborns typically lose 5–7% in the first days and regain birth weight by about two weeks, then gain 20–30 g a day.
Your numbers
Gain
28.1%
Difference
900g
Formula
Gain = (Current weight (g) − Birth weight (g)) ÷ Birth weight (g) × 100
A loss over 10%, or failure to regain birth weight by two weeks, warrants medical review.
What to enter
| Input | Default | Accepted range |
|---|---|---|
| Birth weight (g)Weight at birth, entered in grams. | 3,200 | 500 ~ 6,000 |
| Current weight (g)The weight measured right now. | 4,100 | 500 ~ 20,000 |
Step by step
Quick reference table
Results when only Birth weight (g) changes and everything else stays put.
| Birth weight (g) | Gain (%) | Difference (g) |
|---|---|---|
| 1,600 | 156.3 | 2,500 |
| 2,400 | 70.8 | 1,700 |
| 3,200 | 28.1 | 900 |
| 4,800 | -14.6 | -700 |
| 6,000 | -31.7 | -1,900 |
What each result means
| Result | At default values |
|---|---|
| Gain (%)How much it has grown since birth, as a percentage. | 28.1 |
| Difference (g)The gap between two values — a quantity, not a rate. | 900 |
Common mistakes
A loss over 10%, or failure to regain birth weight by two weeks, warrants medical review.
Glossary
- Birth weight (g)
- Weight at birth, entered in grams.
- Current weight (g)
- The weight measured right now.
- Gain
- How much it has grown since birth, as a percentage.
- Difference
- The gap between two values — a quantity, not a rate.
Frequently asked questions
Q. How is Newborn Weight Gain calculated?
Gain = (Current weight (g) − Birth weight (g)) ÷ Birth weight (g) × 100 — Newborns typically lose 5–7% in the first days and regain birth weight by about two weeks, then gain 20–30 g a day.
Q. Can you walk through an example?
With Birth weight (g) 3,200, Current weight (g) 4,100, the answer is Gain 28.1%.
Q. What do I need to enter?
Enter Birth weight (g), Current weight (g). The result recalculates as you type, and an empty box counts as zero.
Q. How much does the answer move if I change a number?
Changing only Birth weight (g) moves the answer to Birth weight (g) 1,600 → Gain (%) 156.3 and Birth weight (g) 6,000 → Gain (%) -31.7. The table below lays out five steps.
Q. How are the numbers rounded?
Money is shown to the nearest whole unit, percentages to one decimal place and everything else to two. What you see is rounded; the calculation itself carries the unrounded value forward.
Q. Anything to watch out for?
A loss over 10%, or failure to regain birth weight by two weeks, warrants medical review.
Related calculators
These calculators help you understand health figures; they do not replace diagnosis or prescription. See a clinician if you have symptoms.