SCM, LCM and SCY course differences
LCM, SCM and SCY are the three pool courses swimming times are recorded in — a 50 m pool, a 25 m pool and a 25 yd pool. Because the number of turns changes with the pool, the same swimmer posts different times in each, so a time in one course is not directly comparable with a time in another. Here is what the three codes mean, why the times differ, and why a points score has to use the matching course.
Open the Swimming Points calculatorScoring a swim? The Swimming Points calculator asks you to choose the course before it applies the matching base time — so make sure you enter LCM, SCM or SCY to match where the swim was actually raced.
The three course types
Every swim time is tied to the length of the pool it was raced in. Three standard courses are used worldwide, each written as a short code you will see on results, seeding sheets and rankings.
| Code | Pool length | Where used |
|---|---|---|
| LCM — Long Course Metres | 50 m pool | Olympic and World Championship standard; the primary "long course" season worldwide |
| SCM — Short Course Metres | 25 m pool | Short Course World Championships and much of the winter season outside the United States |
| SCY — Short Course Yards | 25 yd pool | The dominant course for United States high school and college (NCAA) swimming |
LCM is the course used at the Olympic Games. SCM and SCY are both "short course" — the same 25-unit pool length — but one measures in metres and the other in yards, so a 25 yd pool is about 8% shorter than a 25 m pool.
Why times differ by course
The reason the same swimmer records different times in each course comes down to turns and push-offs. When you push off a wall you are faster than at any point of free swimming, because the streamlined push and underwater kick carry more speed than stroking on the surface. A shorter pool means more walls over the same race distance, and therefore more of those fast push-offs.
Consider a 100 m race. In a 50 m (LCM) pool you make one turn; in a 25 m (SCM) pool you make three; in a 25 yd (SCY) pool the race distance itself is shorter and there are more turns. Each extra wall shaves time off. That is why a 100 SCY time is not comparable to a 100 LCM time — they are effectively different events with a different number of push-offs, not the same swim measured twice.
Why you cannot naively convert between them
Because the advantage from extra turns depends on the stroke, the distance and even the individual swimmer’s underwater ability, there is no exact conversion from one course to another. You cannot multiply an LCM time by a fixed number and get a true SCM or SCY equivalent.
Governing bodies and swim ranking sites do publish approximate conversion factors to estimate what a swim in one course might be worth in another (for example, the conversion tools described under World Aquatics rule area §4.0). These are useful for rough comparison and seeding, but the output is an estimate only. Any converted time should be clearly labelled as APPROXIMATE and never treated as an official result. We deliberately do not quote specific factors here, because they change with the stroke and distance and are maintained by the governing bodies — the important point is the concept: conversions approximate, they do not equate.
What this means for points
World Aquatics points work by comparing your time against a base time — the benchmark for that event. Crucially, World Aquatics maintains separate base times per course: the base time for the 100 m freestyle long course is different from the base time for the 100 m freestyle short course.
The consequence is simple: points must use the base time for the course the swim was raced in. If you score a short course swim against long course base times, the number is meaningless. And even when computed correctly, a points score is only comparable with another score within the same course and the same table year, because the base times are revised periodically. The mechanics of the score itself are covered in how World Aquatics points are based.
Common mistakes to avoid
Do not put an LCM time next to an SCM or SCY time and call one faster — they are different events. When scoring points, always use the course-specific base time that matches where the swim was raced, and never mix courses in the same comparison. If you must bridge courses, treat any converted time as an approximation, label it clearly, and never present it as an official mark.
Frequently asked questions
Is a SCY time faster than an LCM time?
Typically yes. A short course yards (SCY) race is over a 25-yard pool with more turns and more push-offs than a long course metres (LCM) race in a 50-metre pool, and the wall push is faster than free swimming, so the same swimmer usually posts a faster time in SCY. The two are not directly comparable.
Can I convert a SCM time to an LCM time exactly?
No. There is no exact conversion between courses. Governing bodies and swim sites use approximate conversion factors to estimate an equivalent time, but the result is an approximation only and should always be labelled as such.
Do World Aquatics points work across courses?
Points must use the base time for the matching course. World Aquatics maintains separate base times for long course and short course, so a points score is only comparable with another score computed on the same course and the same table year.
Related tools and reading
Swimming Points calculator
Choose the course, enter your time, and see the World Aquatics points for the matching base time.
ReadHow World Aquatics points are based
The cube-law formula and base times behind a points score, and what keeps the number meaningful.
Sources
- World Aquatics, Swimming Rules — course definitions (long course 50 m, short course 25 m and 25 yd) and the conversion provisions. Checked 24 Aug 2026.