SWOLF Analyzer

{{ poolDisplay }} {{ lapCountDisplay }} {{ averageSplitDisplay }} {{ averageStrokesDisplay }} {{ stabilityBadgeDisplay }} {{ fatigueBadgeDisplay }}

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Course preset:

Select Custom to keep a nonstandard pool length or unit.

Pool length:

Enter a positive pool length; use 25 m, 25 yd, or 50 m for standard courses.

Lap entries:

Use time,strokes per line, such as 25.8,21 or Lap 6, 1:05.4,48.

Rest deduction:

Use seconds per lap, for example 0, 1.5, or 5; it must stay below every split.

Reference block:

Use an opening block for fade checks, or whole-set average for flat-set review.

Segment split:

Choose halves for front/back reads, thirds for pacing shape, or quarters for longer sets.

Drift alert: {{ drift_threshold_pct }}%

Set 2-12%; lower catches small changes, higher shows only larger drift.

Section	Metric	Value	Detail
Review	{{ row.label }}	{{ row.value }}	Set readout metric.
Action cue	{{ item.focus }}	{{ item.finding }}	{{ item.action }}
Segment comparison	{{ segment.label }}	{{ segment.averageSwolfDisplay }}	{{ segment.lapRange }}; split {{ segment.averageTimeDisplay }}; strokes {{ segment.averageStrokesDisplay }}
Notable lap	{{ row.lapLabel }}	{{ row.deltaDisplay }}	{{ row.callLabel }}
Notable lap	Drift threshold	Within threshold	No laps crossed the current drift threshold.

Lap	Split	Strokes	SWOLF	Pace /100	Delta vs ref	Call	Copy
{{ row.lapLabel }}	{{ row.timeDisplay }}	{{ row.strokesDisplay }}	{{ row.swolfDisplay }}	{{ row.paceDisplay }}	{{ row.deltaDisplay }}	{{ row.callLabel }}

Quadrant	Meaning	Copy
{{ item.label }}	{{ item.meaning }}

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A swimmer can make a length faster without making it more efficient. The speed may come from a longer stroke, quicker turnover, a stronger push-off, cleaner body position, or simply more effort. SWOLF gives that tradeoff one compact score by adding the seconds for one pool length to the strokes used on that same length.

The name comes from "swim golf" because a lower score is usually preferable for the same swimmer under the same conditions. That comparison rule matters. A 25 yard freestyle repeat, a 25 meter drill length, and a 50 meter backstroke repeat can all produce valid SWOLF numbers, but they are not interchangeable baselines. Pool course, stroke style, effort target, rest handling, and stroke-count method all change what the score means.

Length: One trip down the pool. SWOLF is normally calculated per length, not for the whole workout at once.
Split: The time recorded for that length. If the split includes wall rest, it should be handled consistently before comparing scores.
Stroke count: The counted strokes for the same length. Watches, goggles, and manual notes may count strokes differently, so repeated comparisons should use the same source.

SWOLF becomes more useful when it is read beside its ingredients instead of replacing them. A lower score from fewer strokes suggests better distance per stroke only if speed stayed close enough. A lower score from a much faster split and extra strokes may be a good sprint choice, but it is a different training signal from cleaner efficiency. The same average can also hide a late fade if early lengths were smooth and closing lengths needed more strokes to hold pace.

The best use is personal trend analysis: compare similar sets, in the same pool course, with the same stroke style and similar rest rules. SWOLF can support coaching notes, pacing checks, and technique experiments, but it is not a universal ranking across swimmers and it cannot explain every cause of a change on its own.

How to Use This Tool:

Enter one pool length per line with a split time and stroke count. The analyzer accepts simple rows such as 25.8,21, clock-style times such as 1:05.4,48, and labeled rows such as Lap 6, 1:05.4,48.

Set Course preset to short-course meters, short-course yards, long-course meters, or Custom. Confirm Pool length and unit because distance, pace, and fair SWOLF comparison depend on the course.
Paste the set into Lap entries. If Check your inputs appears, fix the named lap before using the summary, charts, or exports.
Open Advanced only when the default comparison does not match the set. Use Rest deduction only when the same rest amount was included in every split.
Choose Reference block. Opening blocks work well for fade checks, while Whole-set average is better for reviewing an intentionally even set.
Pick Segment split as halves, thirds, or quarters. Use quarters for longer sets where the closing pattern matters; use halves or thirds when the set has only a few lengths.
Set Drift alert from 2% to 12%, then read Set Readout, SWOLF Lap Ledger, SWOLF Lap Trend, Stroke Economy Map, and Economy Quadrants. Start with the set call, then use the ledger to find the exact length that crossed the alert band.

If a rest deduction removes all swim time from a lap, reduce the deduction or paste splits that already exclude rest before reading the set call.

Interpreting Results:

Start with Average SWOLF, Set call, and Consistency. A lower average is useful only when the set is comparable to the reference you care about. If pool length, stroke style, effort, or rest handling changed, trust the lap trend and quadrant pattern more than the average alone.

The lap labels explain how each length moved against the selected reference. Faster + fewer strokes is the clearest efficiency gain. Faster by turnover may be a deliberate sprint choice or a sign that distance per stroke dropped. Slower + extra strokes is the strongest fatigue cue because both ingredients moved in the wrong direction.

SWOLF result interpretation cues
Result cue	What it usually means	What to verify
`Late fade`	The closing segment rose above the opening segment with slower split time and more strokes.	Check whether the opening lengths were too aggressive, rest was too short, or lane traffic affected the close.
`Stroke creep`	Stroke count rose more clearly than split time while SWOLF trended upward.	Review catch pressure, streamline, and whether a stroke-count target was lost late in the set.
`tight` or `controlled`	SWOLF variation stayed low enough that the average is a more dependable baseline.	Compare the same stroke, course, and effort on a later day before calling it an improvement.
`Above ref` rows	Specific lengths exceeded the active drift alert against the selected reference.	Use the lap ledger to see whether the problem came from split time, stroke count, or both.

Technical Details:

SWOLF is a length-level score, so its unit boundary is the pool length selected for the set. The score does not normalize itself across 25 yard, 25 meter, and 50 meter courses. Pace per 100 can be converted for easier reading, but the SWOLF score itself remains tied to the entered length and stroke-count convention.

The two ingredients can offset each other. A swimmer may lower SWOLF by cutting strokes while holding the same split, by swimming faster with the same count, or by improving both. The same score can also come from different tradeoffs, which is why split delta and stroke delta need to be inspected separately when a set call changes.

Formula Core

t_{adjusted} = t_{split} - t_{rest}

{SWOLF}_{lap} = t_{adjusted} + {strokes}_{lap}

pace = \frac{t_{adjusted}}{pool_length / 100}

CV = \frac{standard_deviation_of_lap_SWOLF}{average_lap_SWOLF} \times 100

A 25 meter length in 26.4 seconds with 22 strokes gives 48.4 SWOLF. If every recorded split includes a 1.0 second wall pause and Rest deduction is set to 1.0, the adjusted split becomes 25.4 seconds and the same row becomes 47.4 SWOLF. Yard entries also produce a normalized pace per 100 meters using 1 yd = 0.9144 m, while the entered-course pace remains shown in yards.

SWOLF derived quantities
Quantity	How it is derived	Why it matters
Reference SWOLF	Average SWOLF from the selected opening block or the whole set.	Baseline for lap deltas, notable laps, recommendations, and the stroke economy map.
Delta vs ref	Lap SWOLF minus reference SWOLF, also shown as a percentage of reference SWOLF.	Shows whether one length was meaningfully better, on line, or above the baseline.
Trend slope	Regression slope across lap number for SWOLF, adjusted split time, and strokes.	Separates a steady set from gradual improvement, tempo drift, stroke creep, or late fade.
Coefficient of variation	Standard deviation of lap SWOLF divided by average lap SWOLF.	Classifies repeat stability as `tight`, `controlled`, `variable`, or `scattered`.

Rule Core

SWOLF status and set call rules
Rule area	Boundary	Result meaning
`Better than ref`	SWOLF delta percent is <= negative `Drift alert`.	The length beat the selected reference by at least the active alert band.
`Above ref`	SWOLF delta percent is >= positive `Drift alert`.	The length moved above the selected reference by at least the active alert band.
Lap call	Split delta uses max `0.25 s` or `1.5%` of reference split; stroke delta uses `0.75` strokes.	Produces calls such as `faster + fewer strokes`, `faster by turnover`, and `slower + extra strokes`.
`Late fade`	Closing segment SWOLF rises by at least max `1.2 SWOLF` or the drift-alert percent of reference, with slower time and more strokes.	The set lost efficiency at the end rather than merely varying by one lap.
Stability	`tight` is CV <= 3.5%; `controlled` is <= 6%; `variable` is <= 9%; higher is `scattered`.	The higher the CV, the less the average should be trusted without lap-level review.

The stroke economy map plots split delta on one axis and stroke delta on the other. Points left of zero were faster than reference; points below zero used fewer strokes. Color follows the SWOLF drift status, and point size grows as the percentage difference from reference becomes larger.

Limitations:

SWOLF is a compact training signal, not a complete stroke analysis. It cannot see body position, breathing pattern, lane traffic, push-off quality, fatigue outside the set, or whether a device miscounted a length or stroke.

Compare like with like: same course, same stroke style, similar effort, and the same rest rules.
Treat cross-swimmer comparisons cautiously because body size, technique, kick strategy, and stroke-count method vary.
Check flagged laps against turns, traffic, equipment changes, or watch errors before treating every spike as a technique problem.
Use SWOLF as training feedback, not as medical advice or a replacement for coaching assessment.

Worked Examples:

Even short-course meters set

Eight 25 meter freestyle lengths around 26.0,21 to 26.6,22 should keep Average SWOLF close to the high 47s or low 48s. With Reference block set to Opening 3 laps and Drift alert at 4%, Consistency should usually land near tight or controlled, and Set call should stay close to Steady hold when no length crosses the alert band.

Yard set with late stroke rise

A 25 yard set that opens near 23.5,18 and closes near 27.0,23 can still have a reasonable average, but SWOLF Lap Ledger will show positive Delta vs ref rows late in the set. The Stroke Economy Map should move closing lengths into the slower and more-strokes quadrant, which supports a pacing or rest change before a full stroke rebuild.

Alert threshold edge

If the selected reference averages 50.0 SWOLF and Drift alert is 4%, a lap at 52.0 SWOLF reaches the Above ref boundary because it is exactly 4% above reference. Raising the alert to 6% would keep that same lap On line, so choose a band that matches how sensitive the workout review should be.

Rest deduction error

If one row is 4.8,12 and Rest deduction is set to 5 seconds, the page reports that the deduction removes all swim time from that lap. Reduce the deduction, remove the bad row, or paste split times that already exclude rest before reading Set Readout.

Advanced Tips:

Use an opening reference block for fade checks, and use the whole-set average when the set was meant to be even from the start.
Set Drift alert lower for controlled technique sets and higher for sprint or race-pace work where small changes are expected.
Compare yard and meter sets with normalized pace, but keep SWOLF comparisons anchored to the same pool course whenever possible.
Use quarters only when the set has enough lengths for each segment to mean something; halves or thirds read better for short repeats.
Check flagged laps against turns, lane traffic, push-offs, and device stroke counts before treating a spike as a technique fault.

FAQ:

Is a lower SWOLF always better?

Lower is usually better for the same swimmer, pool course, stroke style, and effort. It can mislead when a sprint adds strokes for speed, when rest was handled differently, or when the workout goal changed.

Can I compare 25 yard and 25 meter sets?

Use caution. The page shows entered-course pace and normalized meter pace, but SWOLF itself is still based on one entered length, so clean SWOLF comparisons should keep the pool course consistent.

Why can two sets with the same average get different set calls?

The set call also reads segment shift, trend slope, split drift, and stroke drift. One set may hold evenly while another fades late, even if their average SWOLF values match.

What lap entry format should I use?

Use one length per line with time and strokes. Seconds such as 26.2,22, clock times such as 1:05.4,48, and labeled rows such as Lap 6, 1:05.4,48 are accepted when the time and stroke count can be read clearly.

What should I do when the input warning names a lap?

Fix that exact row first. A missing stroke count, unreadable time, nonpositive value, or rest deduction greater than the split leaves the analyzer without a valid length to score.

Glossary:

SWOLF: Split time in seconds plus stroke count for one pool length.
Reference block: The selected baseline, such as the opening lengths or whole-set average, used for lap deltas.
Drift alert: The percentage change from reference SWOLF that marks a length as better than reference or above reference.
Coefficient of variation: A relative measure of how much lap SWOLF varies compared with average lap SWOLF.
Stroke economy map: A chart that separates split-time change from stroke-count change against the selected reference.
Set call: A summary label such as Steady hold, Late fade, or Strong finish based on segment and trend behavior.

References:

Swim Terminology, Garmin.
Swimming metrics, Polar.
What is the difference between FORM Score and SWOLF?, FORM Support Center.

SWOLF Analyzer

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Introduction:

How to Use This Tool:

Interpreting Results:

Technical Details:

Formula Core

Rule Core

Limitations:

Worked Examples:

Even short-course meters set

Yard set with late stroke rise

Alert threshold edge

Rest deduction error

Advanced Tips:

FAQ:

Glossary:

References: