Quick answer: A baby grows fastest in length in the first few months — roughly 25 cm in the first year and another 12 cm in the second year. The average newborn is about 49–50 cm at birth and reaches about 75–76 cm by 12 months and 87–88 cm by 24 months. Any length between the 3rd and 97th percentile on the WHO chart below is medically normal. As with weight, what matters most is that your baby keeps growing along their own line, not which number they sit on. (Under 2 years, length is measured lying down, so “length” and “height” mean the same thing here.)
What “Length-for-Age” Actually Means
Length-for-age (also called height-for-age) compares your baby’s length to the lengths of thousands of healthy, well-nourished children of the same age and sex. It is the single best indicator of long-term, healthy growth: while weight can swing up and down with a single illness or feed, length only ever goes up, and it goes up slowly — so a falling length-for-age trend is an important signal that something has been off for a while.
A percentile tells you where your baby ranks. If your baby is on the 25th percentile for length, it means that out of 100 healthy babies the same age and sex, about 25 would be shorter and 75 would be taller. It is a ranking, not a grade — the 25th percentile is a perfectly healthy place to be.
The WHO Length-for-Age Chart (Birth to 24 Months)
These are the official WHO 2006 Child Growth Standards — the chart the Indian Academy of Pediatrics (IAP) recommends for all Indian children under 5 (adopted in the IAP 2015 Revised Growth Charts). Boys and girls have separate charts because boys are, on average, slightly longer.
- 3rd percentile = the lower edge of normal
- 50th percentile = the median (exactly average — not a target to hit)
- 97th percentile = the upper edge of normal
Anywhere between the 3rd and 97th line is healthy.
Boys — length in cm
| Age | 3rd percentile | 50th (median) | 97th percentile |
|---|---|---|---|
| Birth | 46.3 | 49.9 | 53.4 |
| 1 month | 51.1 | 54.7 | 58.4 |
| 2 months | 54.7 | 58.4 | 62.2 |
| 3 months | 57.6 | 61.4 | 65.3 |
| 4 months | 60.0 | 63.9 | 67.8 |
| 5 months | 61.9 | 65.9 | 69.9 |
| 6 months | 63.6 | 67.6 | 71.6 |
| 7 months | 65.1 | 69.2 | 73.2 |
| 8 months | 66.5 | 70.6 | 74.7 |
| 9 months | 67.7 | 72.0 | 76.2 |
| 10 months | 69.0 | 73.3 | 77.6 |
| 11 months | 70.2 | 74.5 | 78.9 |
| 12 months | 71.3 | 75.7 | 80.2 |
| 15 months | 74.4 | 79.1 | 83.9 |
| 18 months | 77.2 | 82.3 | 87.3 |
| 21 months | 79.7 | 85.1 | 90.5 |
| 24 months | 82.1 | 87.8 | 93.6 |
Girls — length in cm
| Age | 3rd percentile | 50th (median) | 97th percentile |
|---|---|---|---|
| Birth | 45.6 | 49.1 | 52.7 |
| 1 month | 50.0 | 53.7 | 57.4 |
| 2 months | 53.2 | 57.1 | 60.9 |
| 3 months | 55.8 | 59.8 | 63.8 |
| 4 months | 58.0 | 62.1 | 66.2 |
| 5 months | 59.9 | 64.0 | 68.2 |
| 6 months | 61.5 | 65.7 | 70.0 |
| 7 months | 62.9 | 67.3 | 71.6 |
| 8 months | 64.3 | 68.7 | 73.2 |
| 9 months | 65.6 | 70.1 | 74.7 |
| 10 months | 66.8 | 71.5 | 76.1 |
| 11 months | 68.0 | 72.8 | 77.5 |
| 12 months | 69.2 | 74.0 | 78.9 |
| 15 months | 72.4 | 77.5 | 82.7 |
| 18 months | 75.2 | 80.7 | 86.2 |
| 21 months | 77.9 | 83.7 | 89.4 |
| 24 months | 80.3 | 86.4 | 92.5 |
Source: WHO Child Growth Standards — length/height-for-age, boys and girls, birth to 2 years, percentiles (2006). Values from the official WHO percentile tables (boys 0–2y, girls 0–2y), rounded to one decimal place. The IAP 2015 Revised Growth Charts adopted these WHO 2006 standards for all Indian children under 5.
Read it as a range, not a target. If your baby sits steadily on the 15th or 25th percentile for length, that is a perfectly healthy baby who is simply built on the shorter side — often genetically, taking after shorter parents. A baby does not need to reach the 50th percentile.
How Baby Length Is Measured (And Why It Matters)
The way length is measured changes at age 2, and getting it right matters because measuring the wrong way adds or removes up to a centimetre.
- Under 2 years — measured lying down (recumbent length). The baby lies flat on a measuring board (an infantometer), one person holding the head against the fixed end, another straightening the legs and bringing the footboard to the soles. This is why the chart above says “length.”
- 2 years and older — measured standing (stature/height). A child stands against a stadiometer, heels and back to the wall, looking straight ahead.
The WHO standards subtract a fixed 0.7 cm when moving from the lying-down length chart (0–2y) to the standing-height chart (2–5y) — a built-in construction constant, not a measured biological average — which is why the chart steps down slightly at age 2. So always compare like with like: lying-down measurements against the length chart, standing measurements against the height chart.
At home, length is hard to measure accurately — soft tape over a wriggling baby is unreliable. The most consistent number comes from your pediatric clinic with a proper board. Don’t panic over a 1–2 cm difference between measurements; the trend over several visits is what counts.
The Normal Growth Trend, Month by Month
Length gain, like weight gain, starts fast and slows down — but it slows far more smoothly than weight.
0–3 months — the fastest phase
About 3–3.5 cm per month. A newborn of ~50 cm reaches roughly 61 cm by 3 months.
3–6 months
About 2 cm per month.
6–12 months
About 1–1.5 cm per month. Babies grow roughly 25 cm in the whole first year, reaching about 75–76 cm by 12 months.
12–24 months — the second year
About 1 cm per month, totalling roughly 12 cm across the second year, reaching about 87–88 cm by age 2.
| Age band | Average length gain |
|---|---|
| 0–3 months | ~3–3.5 cm / month |
| 3–6 months | ~2 cm / month |
| 6–12 months | ~1–1.5 cm / month |
| 12–24 months | ~1 cm / month |
These are averages. A baby born small may grow faster than this for a while as they catch up, and a baby of tall parents may track high. Your pediatrician looks at the trend on the chart, not any single measurement.
For the matching weight data, see Baby Weight Gain in the First Year: WHO Weight Chart. For head growth — the third key measurement at every check-up — see Average Head Circumference: How Big Is a Baby’s Head?.
What Actually Matters: The Trend, Not One Number
A single length reading tells you very little. Two or three lengths plotted over time tell the whole story.
- A baby following their own curve is healthy — whether that curve is the 10th, 50th, or 90th percentile.
- A baby crossing downward through percentile lines (say, 50th → 25th → 10th over several visits) is what gets a pediatrician’s attention — not a baby who has always tracked along the 10th.
- Genetics set the line. Two short parents very often have a baby on a low length percentile, and that is exactly right for that child.
When to Actually Worry
See your pediatrician if you notice:
- Crossing two or more percentile lines downward for length over several visits
- Length flattening off while weight keeps climbing (or weight dropping first, then length stalling)
- Length consistently below the 3rd percentile, especially if it is also falling
- A big mismatch between length and weight percentiles (for example, weight far below length, which can point to undernutrition)
- Poor length growth together with delayed milestones, poor feeding, or low energy — the combination matters more than any single sign
A baby who is feeding well, active and alert, meeting milestones, and tracking steadily along their own length line is almost always growing fine — even on a low percentile.
Short stature can occasionally signal an underlying issue (nutrition, thyroid, growth hormone, chronic illness, or a genetic condition), but the vast majority of shorter babies are simply healthy and built that way. Only your pediatrician can tell the difference — so when in doubt, get your baby measured rather than guessing. For any urgent concern, contact your pediatrician or the nearest hospital, or call 112 (national emergency) or 108 (ambulance).
India Context: Which Chart, and the “Stunting” Word
Use the WHO 2006 chart (the one above). The IAP has recommended it for all Indian children under 5 since 2015. Older India-specific charts were built on undernourished populations, so they could make genuinely poor growth look “normal” — the WHO standard describes how children should grow in good conditions, anywhere in the world.
In India, persistently low length-for-age (below the 3rd percentile, or more than 2 standard deviations below the median) is what public-health programmes call stunting, and it is usually a sign of long-term undernutrition rather than genetics. This is exactly why pediatricians track length at every visit. It is also why one low reading is not a diagnosis — stunting is about a sustained low-and-falling trend, confirmed by a doctor, not a single number on one day.
Frequently Asked Questions
How long should my baby be at birth?
The average newborn is about 49–50 cm (boys median 49.9 cm, girls median 49.1 cm on the WHO chart). Anywhere from roughly 46 to 53 cm is normal.
How much does a baby grow in length in the first year?
About 25 cm in the first year — fastest in the first three months (~3 cm a month) and slowing to about 1–1.5 cm a month by the end of the year.
My baby is on the 10th percentile for length. Is that bad?
No. The 10th percentile is well within normal. A baby who has tracked along the 10th since birth, feeds well, and is developing normally is a healthy baby — often simply built on the shorter side. Percentiles are a ranking, not a grade.
What’s the difference between length and height on the chart?
It’s just how it’s measured. Under 2 years, babies are measured lying down (length); from 2 years, standing (height). The WHO standards subtract a fixed 0.7 cm when switching from the length chart to the height chart at age 2 (a construction constant, not a biological average), so the chart steps down slightly at that point.
Can short parents have a baby on a low length percentile?
Yes, and it’s expected. Genetics are the biggest driver of height. Two shorter parents very commonly have a baby tracking on a low percentile, and that is the right line for that child.
Which chart should I use — WHO or an Indian chart?
The WHO 2006 chart above. The IAP has recommended it for all Indian children under 5 since 2015. Older Indian charts were based on undernourished populations and can make poor growth look acceptable.
This article is general information for parents in India and follows IAP and WHO 2006 growth guidance. It is not a substitute for an in-person assessment by your pediatrician, who knows your baby’s full history. For any urgent concern, contact your pediatrician or the nearest hospital, or call 112 (national emergency) or 108 (ambulance).
Worried about your baby’s length or growth? Book a consultation with a Babynama pediatrician, or explore our Care Plans for 24/7 expert support.
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