Being in the 98th percentile for height means you (or your child) are taller than 98 out of every 100 people of the same age and sex. Only 2% of the reference population is taller. It’s a way of ranking where someone falls on a growth chart compared to a large group of peers, and it sits at the very top end of the normal range.
How Percentiles Work
A percentile ranks an individual against a reference population. The CDC defines it this way: a percentile indicates what percent of the reference population an individual would equal or exceed. So a 10-year-old boy at the 98th percentile for height is as tall as or taller than 98% of 10-year-old boys in the reference group. He’s shorter than only 2%.
The scale runs from the 1st percentile to the 99th. The 50th percentile represents the statistical middle, the average height for that age and sex. Someone at the 25th percentile isn’t “short” in a medical sense, and someone at the 75th isn’t “tall” in a medical sense. These are all normal positions on the curve. What matters more than any single number is whether a person stays on roughly the same percentile over time, tracking along a consistent growth curve.
Which Growth Chart Is Being Used
In the United States, two sets of growth charts are commonly used, and they don’t always produce the same percentile for the same child. For children under 2 years old, the CDC recommends using the World Health Organization (WHO) growth charts, which are based on an international sample of breastfed infants raised under optimal conditions. For children and teens aged 2 to 19, the CDC’s own growth charts are recommended. These were built from U.S. national survey data collected between 1963 and 1980.
The two charts can give slightly different readings, especially at the extremes. The WHO charts use the 97.7th percentile (equivalent to +2 standard deviations) as an upper screening boundary, while the CDC charts traditionally use the 95th. A child plotted at the 98th on one chart might land slightly differently on the other. If you’re comparing numbers from different doctor visits or different countries, the chart system matters.
What the 98th Percentile Means in Practice
For most people, being at the 98th percentile is simply the tall end of normal. Height is heavily influenced by genetics. If both parents are tall, a child tracking along the 98th percentile is doing exactly what their DNA predicts. Pediatricians look at “midparental height,” a calculation based on both biological parents’ heights, to estimate where a child should end up. A child whose projected adult height is within two standard deviations of that midparental target is generally considered to be growing normally, regardless of how high the percentile number looks.
To put the 98th percentile in concrete terms: for a 10-year-old boy in the U.S., it corresponds to roughly 57.5 inches (about 4 feet 9.5 inches). For a 10-year-old girl, it’s roughly 57 inches. These numbers shift at every age, which is why the charts exist. By adulthood, a man at the 98th percentile is approximately 6 feet 3 inches, and a woman is approximately 5 feet 10 inches.
Why the Trend Matters More Than One Reading
A single percentile reading is a snapshot. What pediatricians actually care about is the trend over time. A child who has been at the 98th percentile since infancy and stays there is following a consistent growth pattern. That’s reassuring. A child who was at the 50th percentile at age 3 and has jumped to the 98th by age 6 is crossing percentile lines, which can signal something worth investigating.
Growth velocity, the rate at which height increases over a given period, tells a more complete story than any single point on the chart. A child steadily tracking along any percentile, whether it’s the 10th or the 98th, is typically growing at a healthy, predictable pace. Sudden upward or downward shifts are what prompt closer evaluation.
When Tall Stature Gets a Closer Look
Tall stature is formally defined as a height more than two standard deviations above the average for age, which corresponds to roughly the 97th percentile. The 98th percentile sits just above this threshold, so it can sometimes trigger a conversation with your pediatrician, especially if the height seems out of proportion with the family’s genetic background.
Most children above the 97th percentile have what’s called constitutional tall stature, meaning they’re tall because their parents are tall. No medical issue is involved. Evaluation is more likely to be recommended when a child’s projected adult height is more than two standard deviations above the midparental height, or when the child has crossed multiple percentile lines in a short time. Children who are more than three standard deviations above the mean (well above the 99th percentile) are more likely to have an underlying condition contributing to their growth.
In rare cases, extremely rapid growth can be caused by excess growth hormone produced by the pituitary gland, a condition called gigantism in children. Signs that distinguish this from normal tallness include a very prominent forehead and jaw, widening gaps between teeth, thickening of facial features, and unusually large hands and feet. These physical changes are quite distinct from simply being a tall kid. Providers typically suspect this condition when a child’s height is three standard deviations above average or two standard deviations above the expected height based on parental genetics.
Understanding Z-Scores
You might also hear your doctor mention a z-score alongside a percentile. A z-score measures how many standard deviations a measurement is from the average. A z-score of 0 is exactly average (50th percentile). A z-score of +2 corresponds roughly to the 97.7th percentile, and a z-score of +2.05 to +2.1 lands close to the 98th percentile.
Z-scores are especially useful at the extremes of the growth chart. Once a child is above the 99th percentile, the percentile number stops being very informative because there’s no higher line on the chart. A z-score of +2.5 versus +3.5 communicates a meaningful difference that “above the 99th percentile” doesn’t capture. For most parents, percentiles are easier to understand, but z-scores give clinicians a more precise tool when growth falls far from the middle of the curve.