Average Height for Boys Aged 18 Years 6 Months

At 18 years 6 months, the median in the CDC table for boys is 176.4 cm (5 ft 9.5 in), which is 99.8% of the median at age 20 (176.8 cm). The 3rd percentile is 162.8 cm and the 97th is 189.7 cm.

CDC standing stature percentiles for boys aged 18 years 6 months. Source: CDC 2000 Growth Charts: stature-for-age, 2-20 years, file statage.csv, row Sex=1, Agemos=222.5 (completed month 222 band) (dataset page).
PercentileMetricFeet-inches
3rd162.8 cm5 ft 4.1 in
5th164.6 cm5 ft 4.8 in
10th167.2 cm5 ft 5.8 in
25th171.6 cm5 ft 7.6 in
50th176.4 cm5 ft 9.5 in
75th181.2 cm5 ft 11.4 in
90th185.5 cm6 ft 1.0 in
95th188.1 cm6 ft 2.0 in
97th189.7 cm6 ft 2.7 in
CDC height reference for boys aged 18 years 6 months, showing the 3rd through 97th percentiles in centimeters and feet-inches.

Check a height against this row

or

Accepts 147.1 to 204.4 cm.

3rd5th10th25th50th75th90th95th97th 162.8164.6167.2171.6176.4181.2185.5188.1189.7

How much the median still changes after 18 years 6 months

Six months on, the median is 176.6 cm, a change of 0.2 cm; a year on it is 176.8 cm, a change of 0.4 cm. From this age to 20 the table adds 0.4 cm to the median in total.

Every 12-month gain in the boys' median that starts at 16 years 11 months or later is under 1 cm. The largest 12-month gain after age 6 is 7.8 cm, from 12 years 9 months, so the steep part of the table is already behind this age.

Across the next 12 months the lowest line shown, the 3rd percentile, moves up 0.4 cm, and the highest, the 97th, moves up 0.4 cm. The two lines move almost in step, so the gap stays near 26.9 cm.

Nearby rows of the CDC stature-for-age table for boys, in centimeters. The last column is the change in the median since the row above.
Age3rd50th97thChange
16 years 6 months160.3174.6188.0
17 years 6 months162.0175.8189.1+1.2
18 years162.5176.2189.5+0.4
18 years 6 months162.8176.4189.7+0.2
19 years163.1176.6189.9+0.2
19 years 6 months163.2176.8190.1+0.2
20 years163.3176.8190.2+0.0

Where the 3rd and 97th percentiles sit

The middle half of the reference, from the 25th to the 75th percentile, spans 9.6 cm; the 3rd-to-97th range spans 26.9 cm. For boys, that range is widest at 13 years 9 months (30.3 cm).

Measured against younger boys, a boy aged 18 years 6 months on the 3rd percentile (162.8 cm) roughly matches the median boy of 13 years 10 months (162.9 cm). The 97th-percentile height (189.7 cm) is 12.9 cm above the median at 20 (176.8 cm).

Boys and girls at 18 years 6 months

Girls of the same age have a median of 163.2 cm, 13.2 cm below the boys' median. At 20 the gap between the two medians is 13.5 cm. The girls' median is higher than the boys' only from 10 years 9 months to 13 years 2 months.

When to talk to a doctor

If growth has slowed unexpectedly, a teen is crossing downward through percentile lines, or puberty seems unusually early or late, speak to a pediatrician or family doctor. A percentile on its own is not a diagnosis or a measure of health.

Reference values only, not medical advice. How these tables are built.