How much should my child’s swim times improve each year?

Based on more than 100,000 Australian race results (2022–2026), the median year-on-year improvement is about 11% at age 8–9, 7–9% through ages 9–11, 4–6% at 11–14, and under 3% from age 14 onwards. Half of all swimmers fall inside a wide band around these medians, so slower years are normal.

Is it normal for a teenage swimmer to plateau?

Yes. By ages 15–16 the median improvement is 1.7% per year, and a quarter of swimmers are slightly slower than the previous season. Plateaus at this age reflect maturation, not lack of effort, and are consistent with published research on adolescent swimming performance.

Which stroke improves fastest in young swimmers?

Butterfly. At every age band in the Australian data, butterfly shows the largest median year-on-year improvement — 10.0% at ages 8–10 versus 8.2% for freestyle — because technique gains compound more in the technically hardest strokes.

Do boys and girls improve at the same rate?

They start similarly (9.1% vs 8.2% at ages 8–10) but diverge in the early teens: at ages 14–16 the median improvement is 3.1% per year for boys and 0.7% for girls. Girls typically reach physical maturity earlier, so their times stabilise sooner — this is normal development, not underperformance.

Australian data · 2022–2026

How much do age-group swimmers improve each year?

Median year-on-year improvement from more than 100,000 Australian race results: about 11% at age 8–9, falling to under 2% by age 16. Here is the full curve — by age, stroke, and gender.

Age-group swimmers improve fastest between ages 8 and 11, and the rate of improvement roughly halves every three years after that. Across more than 100,000 Australian race results (2022–2026), the median swimmer dropped 11.2% off their times between ages 8 and 9 — but only 1.7% between 15 and 16. If your swimmer's improvement is slowing as they get older, that is the normal shape of development, not a warning sign.

Improvement by age

Each row compares a swimmer's best time in an event at one age with their best time in the same event and course a year later. The middle-50% band shows how wide normal is: at every age, a quarter of swimmers improve much faster than the median and a quarter improve much slower — including, in the teens, some who go backwards for a season.

Median year-on-year PB improvement, 50–400m events, all strokes, LCM + SCM · 15,000+ season pairs
Age	Median improvement	Middle 50% of swimmers	Swimmers
8 → 9	11.2%	7.5% – 15.4%	200+
9 → 10	8.7%	5.1% – 13.0%	350+
10 → 11	7.3%	3.9% – 11.2%	400+
11 → 12	6.1%	2.9% – 9.4%	350+
12 → 13	4.9%	2.0% – 8.5%	300+
13 → 14	4.0%	1.5% – 6.9%	200+
14 → 15	2.6%	0.5% – 5.2%	150+
15 → 16	1.7%	−0.3% – 4.1%	100+
16 → 17	1.3%	−0.5% – 3.6%	50+

Method: for every swimmer we take their best time per event, course, and age (age at race date), and compare consecutive ages. Percentages are median time drops across all such pairs. Ages 17–18 are excluded (sample too small). Data: publicly available Australian competition results, anonymised and aggregated. Computed 5 July 2026.

Butterfly improves fastest — at every age

The technically hardest strokes reward practice the most. Butterfly leads the improvement table in every age band, and breaststroke — the other high-technique stroke — is second in the younger years. Freestyle improves slowest, largely because young swimmers start with more freestyle experience, leaving less easy technique gain on the table.

Median year-on-year improvement by stroke and age band
Stroke	Ages 8–10	Ages 11–13	Ages 14–16
Butterfly	10.0%	5.8%	3.1%
Breaststroke	9.0%	5.5%	2.3%
Backstroke	8.3%	5.0%	2.1%
Freestyle	8.2%	4.9%	2.0%
Individual Medley	8.2%	4.9%	2.0%

Boys and girls diverge in the early teens

At ages 8–10 the two curves are close. From 11 onwards they separate: boys keep improving at a median 6.4% per year through 11–13 and 3.1% through 14–16, while girls slow to 3.9% and then 0.7%. Girls typically reach physical maturity earlier, so their times stabilise sooner. A 15-year-old girl holding her times steady is developing normally — the field around her is doing the same.

Median year-on-year improvement by gender and age band
	Ages 8–10	Ages 11–13	Ages 14–16
Boys	9.1%	6.4%	3.1%
Girls	8.2%	3.9%	0.7%

What this means for your swimmer

Two practical takeaways. First, judge improvement against the right baseline: an 8% drop is ordinary for a 9-year-old and exceptional for a 15-year-old. Second, a flat season inside the middle-50% band is not a plateau problem — it is where a large share of swimmers sit every year. The signal worth watching is the trend across multiple seasons and events, not any single race.

These findings match peer-reviewed research on adolescent swimming performance, which reports roughly 9–10% annual improvement at ages 8–10, about 5% at 11–14, and 1–2% at 15–18 — but the numbers above are Australian, current, and broken down by stroke and gender. For where your swimmer sits today, see our benchmark times by age, or use the QT calculator to check how close they are to qualifying for their next championship.

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