Girls' growth timeline
| Age | What usually happens |
|---|---|
| 8–13 | Puberty starts (first sign: breast buds) |
| 9–11 | Growth speeds up |
| 11–12 | Peak growth |
| ~12–13 | First period, about a year after peak growth |
| 14–16 | Growth plates close; height stops |
Healthy girls can be two years either side of these ages.
Why the first period is a useful marker
Periods start after the fastest phase of growth, so by then most of a girl's height gain is behind her. Rising estrogen is also what eventually closes the growth plates. That makes "years since first period" a practical guide: in the first year there is usually real growth left, and two to three years after, very little.
How to estimate adult height
The height predictor uses age, height, weight and both parents' heights. For girls the Khamis-Roche method is accurate to about ±4.3 cm 90% of the time, a little tighter than for boys because girls' growth is more predictable once puberty is under way.
