Short Course vs Long Course

Moving from a 25m to a 50m pool keeps the workout distance in metres unchanged, but means fewer turns and longer stretches of swimming between walls. Recheck your effort, repeat times and recovery rather than forcing your short-course intervals onto the longer pool.

What is the difference between SCY, SCM and LCM?

Short course describes a 25-yard or 25-metre pool; long course describes a 50-metre pool. USMS identifies 25 yards as the standard U.S. short-course competitive length and distinguishes it from 25 metres. The unit matters as much as the number.

Three course formats

Distance check	SCY	SCM	LCM
One length	25 yards	25 metres	50 metres
Four lengths	100 yards	100 metres	200 metres
100 in that course’s unit	4 lengths	4 lengths	2 lengths
Turns within that 100	3	3	1

Here, a length means one trip from wall to wall. Write that word on your session sheet instead of relying on an ambiguous “lap”. Confirm the current lane setup with the facility, especially when a movable bulkhead changes the course. For the separate issue of changing units, see our metres-to-yards workout guide .

How do lengths and turns change from 25m to 50m?

Divide the distance by the pool length, then subtract one to count turns within a continuous swim. This original arithmetic assumes a wall start, whole lengths and no stops mid-repeat: the starting push-off is not a turn, and the final touch ends the swim.

100m: 100 ÷ 25 = 4 lengths and 3 turns; 100 ÷ 50 = 2 lengths and 1 turn.
200m: 200 ÷ 25 = 8 lengths and 7 turns; 200 ÷ 50 = 4 lengths and 3 turns.
400m: 400 ÷ 25 = 16 lengths and 15 turns; 400 ÷ 50 = 8 lengths and 7 turns.

For repeated swims, calculate turns inside each repeat, then multiply by the repeat count. Resting at a wall and starting again is a new repeat, so a broken-up distance has a different turn count from one continuous swim. Also check short drill segments: a 25m segment ends halfway down a 50m lane. Rewrite it to finish at a wall, and recalculate the session total if that changes its distance.

Why can the same distance feel harder in a 50m pool?

There are fewer wall-assisted transitions and longer uninterrupted stretches of stroking. The USMS transition article highlights how walls can mask efficiency issues and recommends paying attention to stroke efficiency, streamlines, transitions and breathing when changing course.

Its starting example is a move from yards to metres, which also changes the distance of a numbered repeat. A 25m-to-50m move removes that unit change: 100m still means 100m. Even so, matching the distance does not make the wall pattern or effort identical. Notice where your stroke becomes rushed rather than interpreting one slower session as lost fitness.

How should I adjust pace, rest and send-offs?

Start by preserving the intended effort and recovery, then use the times you actually swim to choose intervals. This is a practical editorial approach, not a race-time conversion formula or a promise of a particular adjustment.

Recheck in this order

Confirm the course and rewrite lengths Keep metres as metres. Check every repeat and drill ends at a usable wall, then confirm the revised total before swimming.
Swim at the intended effort Begin with controlled swimming and record repeat times. Avoid speeding up merely to reproduce a familiar short-course split.
Check how much recovery remains A send-off includes both swim time and rest. If a 2:00 send-off used to leave 20 seconds after a 1:40 swim, a hypothetical 1:48 swim leaves only 12 seconds. A 2:08 send-off would restore 20 seconds; those numbers illustrate arithmetic, not a recommended conversion.
Set the next session from those observations Use repeatable times and manageable technique to choose the next send-off. If the planned workload is too demanding, reduce it or add recovery rather than forcing the old clock target.

Keep pool format beside your pace notes so future comparisons have context. For more on the clock calculation, use the send-off interval guide. A distance conversion cannot by itself predict race performance across courses.

What could a first 50m-pool workout look like?

This original 700m AquaPlan example uses rest after swimming rather than fixed send-offs, leaving room to observe your new pace. It is for swimmers already comfortable completing 100m continuously; shorten or skip it if that does not fit your current ability. It is not a USMS-prescribed or tested programme.

First long-course pace check

Original easy training example, not a time trial · 700m total

4 × 50m Easy warm-up — GA1 · Rest 20s between repeats · Rest 30s after the set · One length per repeat. Start gently; take more rest whenever needed.
4 × 100m Repeatable easy swimming — GA1 · Rest 30s between repeats · Rest 30s after the set · Two lengths and one turn per repeat. Record each swim time without chasing your 25m-pool pace. Reduce effort or end the set if technique becomes difficult to maintain.
2 × 50m Very easy finish — ReKom · Rest 20s between repeats · One length per repeat. Keep this relaxed.

The total is 200m warm-up + 400m main work + 100m easy finish = 700m, or 14 lengths in a 50m pool. Each main repeat has one turn. To reuse the distances in a 25m pool, set the pool length to 25m: the session becomes 28 lengths and each 100m main repeat has three turns. Recheck effort there too.

Use the workout’s Open in builder control or build a session for your actual pool length . Choose distances that finish at the wall, then check the repeat counts, rest and total before taking the session poolside. For other starting points, browse free swim workouts.

Training choice

Keep the purpose of the session; recalibrate the clock.

A move from 25m to 50m changes the pattern of swimming and turns. Preserve the planned distance only when it remains manageable, and choose intervals from your observed effort and recovery in the new pool.

Frequently Asked Questions

What do SCY, SCM and LCM mean in swimming?

SCY means short course yards, a 25-yard pool. SCM means short course metres, a 25-metre pool. LCM means long course metres, a 50-metre pool. Check the actual lane configuration before counting lengths.

How many lengths is 100 metres in a 50-metre pool?

Two lengths, with one turn between them. In a 25-metre pool, 100 metres is four lengths with three turns. The final touch is a finish, not another turn.

Should I halve my workout distance when moving from 25m to 50m?

No. Halve the number of lengths for the same distance in metres. A 400m swim remains 400m: 16 lengths in a 25m pool or eight in a 50m pool. Separately, reduce the planned workload if the longer uninterrupted swimming is too demanding.

Can I convert my short-course pace directly into long-course pace?

Do not assume a fixed seconds-per-100 adjustment predicts your performance. The change depends on your turns, stroke and effort. Use an initial long-course session to record repeat times and recovery, then set intervals appropriate to that pool.

Sources and editorial process

Sources checked October 23, 2026: the USMS pool-length guide and transition article below. Course definitions and transition principles come from those references; length and turn calculations, interval arithmetic and the sample workout are original AquaPlan editorial examples.

Limitations: these sources do not establish a universal race-performance conversion or individual pace adjustment. No first-hand testing, individual stroke assessment or guaranteed training result is claimed.

Automated editorial check (daily-ai-v1): this article was authored using AI and checked through an automated editorial process. No human expert review is claimed.

Article publisher

Published and maintained by AquaPlan. The article above identifies its evidence sources and automated editorial process; no human expert review is claimed.