SWOLF Analyzer

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

Check your inputs

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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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SWOLF is a compact pool-swimming score made from one length's split time plus the strokes used to cover that length. It is useful because it turns repeat lengths into something you can compare quickly, but a single average can still hide the story of a whole set.

A session can start smooth and finish ragged, or it can settle down after a scratchy opening. The headline average may barely move while the actual pattern changes a lot. That is the gap this page tries to close. Instead of stopping at one number, it reads a full set lap by lap and then shows where the score drifted, where stroke count changed first, and whether the back half held together.

You enter one pool length per line as time and strokes, choose meters or yards, and optionally add a course preset, a fixed rest deduction, a reference block, a segment split, and a drift alert band. The result is not just an average SWOLF. It is a set readout, a lap table, a trend chart, a stroke economy map, and a structured JSON record built from the same set.

The Set Readout and Lap Table tabs can be copied as CSV, downloaded as CSV, or exported to DOCX. The two charts can be saved as PNG, WebP, JPEG, or CSV. That makes the page practical for training notes, coach review, or simple week-to-week comparison without forcing you to rebuild the same summary by hand.

SWOLF still needs a fair comparison to mean much. Lower usually points to a more efficient length for the same distance and stroke style, but the comparison weakens fast when pool size, workout purpose, effort level, or rest handling changes. All routine calculation stays in the browser after the page loads, so privacy is straightforward, but the quality of the result still depends on clean lap entries and an honest baseline.

Technical Details

Each input line is treated as one pool length. The parser accepts plain seconds, minute-based times, optional labels, and several simple separators, so entries such as 25.8,21, 1:05.4,48, or Lap 6, 26.1,22 all resolve to the same two core values: split time and stroke count.

If you set a rest deduction, the same fixed number of seconds is removed from every entered split before scoring. That is useful when each repeat includes a small, repeatable wall pause. It is not a general cleanup switch for irregular timing. If the deduction would remove all swim time from any lap, the page stops and asks for a correction instead of quietly producing nonsense.

\begin{array}{lcl} t_{adjusted} & = & t_{entered} - t_{rest} \\ SWOLF & = & t_{adjusted} + strokes \\ {Pace}_{100 pool} & = & \frac{t_{adjusted}}{pool length / 100} \\ {Pace}_{100 m} & = & \frac{t_{adjusted}}{pool length in meters / 100} \end{array}

The baseline is selectable because the opening of a set is not always the right comparison point. You can measure every lap against the opening two lengths, opening three lengths, the opening third, or the whole-set average. The same set can also be broken into halves, thirds, or quarters so the opening and closing blocks can be compared directly instead of guessed from memory.

The trend chart plots four lines: SWOLF, strokes, split time, and the reference SWOLF. The stroke economy map uses split delta on one axis and stroke delta on the other, colors laps by whether they are better than reference, on line, or above reference, and grows point size as SWOLF deviation gets larger. Together those two views answer slightly different questions. One asks whether the set drifted. The other asks what drove the drift.

How the stroke economy map reads a lap

Faster + fewer

Split time and stroke count both improved against the reference block.

Faster by turnover

The lap got faster, but it needed more strokes to get there.

Longer but slower

Stroke count dropped, yet the split still drifted slower than baseline.

Slower + extra strokes

Both split time and stroke count rose, which is the clearest fatigue pattern in this tool.

Tool-defined SWOLF label bands
Layer	Rule used here	What the label means on the page
Lap status	`Better than ref`, `On line`, or `Above ref` based on the chosen drift alert percentage.	Shows whether a lap moved meaningfully away from the baseline you selected.
Consistency	`tight` at 3.5% CV or lower, `controlled` up to 6%, `variable` up to 9%, then `scattered`.	Rates how trustworthy the set average is as a repeatable comparison point.
Normalized pace	Always computed in meters, but surfaced in `Set Readout` when the entered pool is in yards.	Helps compare yard sessions with meter sessions without changing the original pool-unit pace.
JSON export	Includes inputs, computed metrics, reference summary, segment summaries, recommendations, and lap-by-lap deltas.	Lets you keep a structured record of the same analysis without re-entering the set later.

Set call logic used by the SWOLF analyzer
Set call	What usually triggers it here	Plain-language reading
Strong finish	The closing segment beats the opening segment by at least the active SWOLF threshold without getting slower or stroke-heavier.	The set cleaned up as it went on.
Late fade	The closing segment is worse than the opening segment by the active threshold, with slower time and more strokes.	The back end lost efficiency and pace together.
Tempo drift	Split time rises across the set more clearly than stroke count while SWOLF still trends upward.	Speed slipped first.
Stroke creep	Stroke count rises more clearly than split time while SWOLF still trends upward.	Turnover increased to hold the pace line.
Building into set	Overall SWOLF trend slopes downward without matching the stronger finish conditions above.	The set improved after the opening lengths.
Steady hold	No stronger fade or improvement pattern wins.	The set stayed broadly stable around its opening standard.

Everyday Use & Decision Guide

Start with the comparison you actually care about. If you want to know whether a set fell apart after a good opening, use an opening reference. If the whole set was meant to be flat from the first length to the last, the whole-set average can be a fairer baseline. Most bad SWOLF interpretation begins with the wrong reference block, not with the wrong arithmetic.

The quickest reading order is the summary box, then Set Readout, then the two charts. The summary tells you the average SWOLF, pool course, lap count, pace, average strokes, stability label, and fatigue badge. Set Readout adds total distance, spread, trend slopes, best detail, segment comparison, notable laps, and three action cues. That is usually enough for a session note. Open Lap Table when you need to know which exact lengths crossed the alert band.

The chart tabs answer more specific questions. Trend Chart is best when you want to see a steady rise, a late fade, or a cleaner second half. Stroke Economy Map is better when you want to separate slower time from rising stroke count. A worse SWOLF can come from one of those changes or both, and the next coaching decision is different in each case.

Keep the set consistent. SWOLF is most useful when the lengths share the same stroke style and training purpose.
Use rest deduction only for repeatable wall pauses. It should not be used to repair irregular stopwatch splits after the fact.
In yard pools, read the normalized meter pace as a comparison aid, not as a replacement for the pool-unit pace you actually swam.
If the set is marked variable or scattered, read the flagged laps before trusting the average.

The export layout also suggests how the tool wants to be used. Set Readout and Lap Table exports are good for notes and coach share-outs. Chart image exports are good when the picture matters more than the raw rows. JSON is the better choice when you want to keep the whole state, including the reference choice, thresholds, segment summaries, and lap-level deltas.

Step-by-Step Guide

Choose the pool length manually or use a short-course meters, short-course yards, or long-course meters preset.
Paste one length per line as time and strokes. Do not mix different strokes or different workout purposes in the same readout.
Add a rest deduction only if every lap includes roughly the same brief pause at the wall.
Pick the reference block that matches the question you are asking, then choose halves, thirds, or quarters for the segment summary.
Set the drift alert percentage, from 2% to 12%, to define how large a SWOLF change should count as meaningfully better or worse.
Read the summary box and Set Readout first, then use Lap Table, Trend Chart, and Stroke Economy Map to check where the pattern came from.
Export CSV, DOCX, chart files, or JSON only after the baseline and threshold settings match the comparison you actually want to keep.

Interpreting Results

SWOLF is best treated as an indirect efficiency check, not as a universal grade. A lower number can point to cleaner swimming, but it can also reflect a different effort level, a different stroke, or a different pool setup. The tool is strongest when it compares you with yourself across similar pool sets, not when it tries to rank swimmers against each other.

How to read common SWOLF patterns
Visible cue	Best first reading	What to check next
Better than reference, but with more strokes	You swam faster, but the gain came from higher turnover.	Use the economy map to decide whether that tradeoff was intentional or expensive.
Slower, but with fewer strokes	The lap lengthened out, yet pace still slipped.	Check whether the stroke got too patient or the push-off quality changed.
Late fade	The closing block lost time and needed more strokes.	Review pacing, rest, and whether fatigue changed the stroke under pressure.
Tempo drift	Speed faded before stroke count rose much.	Look at pace control and walls before assuming a technique breakdown.
Stroke creep	Stroke count climbed to hold the line.	Check whether stroke length, catch quality, or body position slipped first.
Tight or controlled consistency	The average is stable enough to reuse as a future benchmark.	Compare the same stroke, pool length, and session intent next time.
Variable or scattered consistency	The average is real, but it may hide very different lengths inside the set.	Open the flagged laps and chart views before drawing a coaching conclusion.

The drift alert is a working threshold, not a governing swim standard. Setting it lower makes the page more sensitive. Setting it higher makes it more selective. The same is true for the stability labels and set calls. They help organize the session, but they do not replace your knowledge of whether the set was meant to be smooth, descending, broken by rest, or swum at mixed intensities.

One outlier should not automatically rewrite the whole session. A weak turn, a traffic check, or one bad stroke count can push a single length across the alert band. The tool handles that by showing notable laps separately from the set call, so you can decide whether a flagged repeat is the main story or just a noisy exception.

Worked Examples

A flat short-course meters set

Suppose an eight-length front-crawl set in a 25 meter pool opens around 48 SWOLF and stays within a few percent of that mark from start to finish. The page will usually land on Steady hold, show few or no flagged laps, and rate consistency as tight or controlled. That is the kind of set where the average is worth saving as a baseline.

A yard set that fades late

Now imagine a 25 yard set where the opening three lengths sit near the reference, but the closing half gets slower by about half a second per lap and adds one or two strokes. The tool will often label that Late fade, surface those lengths in the notable-laps table, and show the closing drift clearly on both charts. The normalized meter pace in the review helps later if you want to compare that yard session with a meter pool set.

A set that improves after the opening

Consider a set where the first few lengths are rushed, but the middle and closing block settle into lower SWOLF with the same or better split time. The average alone may look ordinary. The segment rows and trend slope tell the real story. Depending on how strong the closing improvement is, the set call can move toward Building into set or Strong finish, which is a very different training read from a fade.

FAQ:

Can I compare my SWOLF with another swimmer's score?

That is usually a bad use of the metric. SWOLF is highly individual and becomes more useful when it compares your own repeats under similar pool conditions.

Why does pool length matter so much?

Pool length affects split time, pace, stroke count, and the final SWOLF score. A 25 yard length and a 25 meter length are not interchangeable, which is why the tool asks for the course up front and keeps a normalized meter pace for cross-course comparison.

When should I use the whole-set average as the reference?

Use it when the set was meant to be broadly even and you want every lap judged against the session's overall standard. Use an opening reference when the question is whether the set held, faded, or improved after the start.

Do fewer strokes always mean a better lap?

No. Fewer strokes can still come with a slower split. The economy map helps separate cleaner efficiency from a lap that simply glided longer and lost speed.

Can I paste lap lines that include labels or watch-style formatting?

Usually yes, as long as each line still contains one readable time value and one readable stroke count. Optional lap labels and several simple separators are accepted.

Is any of my lap data uploaded for scoring?

No dedicated scoring backend is used here. The set readout, tables, charts, exports, and JSON payload are generated in the browser after the page loads.

Glossary:

SWOLF: A pool-length score made from adjusted split time plus stroke count for that same length.
Reference block: The opening or whole-set slice used as the baseline for lap-by-lap drift.
Drift alert: The percentage change from reference SWOLF that the page treats as meaningfully better or worse.
Coefficient of variation: A relative measure of how much SWOLF varies across the set compared with the set average.
Stroke economy map: A scatter view that compares split delta with stroke delta so each lap can be read as faster or slower and fewer or more strokes.
Normalized pace: The pace recalculated per 100 meters so yard and meter sessions can be compared more fairly afterward.

References:

Swim Terminology, Garmin.
V800 User Manual: Swimming Metrics, Polar.