Race Pace and Finish Time Suite

Planning mode:

The mode changes the input path while the split tables, charts, and exports stay in one suite.

Split ladder unit:

Match race markers, watch alerts, or crew notes with kilometre or mile splits.

Pacing profile:

Use even pace for baseline checks, then compare controlled starts, negative splits, or late fade.

Finish adjustment:

Positive values slow the estimate; negative values speed it up. Default 0% is neutral.

{{ finish_adjustment_percent }}%

Riegel exponent:

Lower holds speed better over longer distances; higher assumes more slowdown.

Planned stops:

Leave at 0 for continuous running, or add a pause budget for longer events.

stops sec each

Stop placement:

Pace plan brief metrics
Metric	Value	Planning note	Copy
{{ row.metric }}	{{ row.value }}	{{ row.note }}

Race split ladder
Checkpoint	Distance	Split pace	Segment time	Cumulative time	Note	Copy
{{ row.checkpoint }}	{{ row.distance }}	{{ row.pace }}	{{ row.segmentTime }}	{{ row.cumulative }}	{{ row.note }}

Adjustment scenario guide
Scenario	Finish	Average pace	Vs baseline	Planning note	Copy
{{ row.scenario }}	{{ row.finish }}	{{ row.pace }}	{{ row.delta }}	{{ row.note }}

Pace band ladder
Band	Finish	Average pace	Vs plan	Planning note	Copy
{{ row.band }}	{{ row.finish }}	{{ row.pace }}	{{ row.delta }}	{{ row.note }}

Enter a positive race distance and a valid time, pace, speed, or training profile to build the pace plan.

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Race pace is the link between distance and elapsed time. A finish goal only becomes useful when it turns into steady pace, checkpoints, and a realistic view of where time can be gained or lost. That matters for a 10 km watch target, a half-marathon pacing band, a marathon crew sheet, or an ultra plan where small pacing errors can grow across many miles.

Different planning questions need different evidence. A target pace or treadmill speed is enough when the goal is already chosen. A recent race result can estimate another distance when both races reflect the same fitness. A marathon training block can provide a rough estimate from recent running volume, average training speed, and run frequency, but it cannot prove fueling, durability, heat response, or course readiness.

Flow from race evidence to a base finish clock, race assumptions, split checkpoints, and scenario comparisons.

Road races also have measurement realities that pace math cannot solve. Official marathon and half-marathon distances are fixed, but GPS watches, tangents, crowds, aid stations, weather, hills, and late-race fatigue can all move the lived result away from the clean arithmetic. A pace plan is strongest when it is treated as a checked estimate, not a guarantee.

The safest reading is a range plus a plan. Use a single projected finish to set the first draft, then test how the plan changes when the race day is harder, a stop budget is added, or the reference race is a bigger stretch than it first appears.

Technical Details:

Race pace uses one governing relationship: time equals distance multiplied by pace. When distance is fixed, every change in average pace produces a proportional change in finish time. Speed is the inverse view of the same result, so 12.0 km/h becomes 5:00 per kilometre and about 8:03 per mile.

Race prediction adds a distance-power curve. The Riegel equation scales a known race time by the ratio between target distance and reference distance, raised to an exponent. An exponent above 1 means the predicted time grows slightly faster than distance, which reflects the normal slowdown as races get longer. The default exponent is 1.06, while the editable range from 0.90 to 1.20 lets a runner test stronger or weaker long-distance conversion.

Training-based marathon estimates are more fragile because training summaries hide many race-day variables. The formula used here is a fixed linear model in minutes. Weekly distance is normalized to kilometres, training speed to kilometres per hour, and run count to runs per week before the marathon clock is produced. If that model returns a non-positive time, no result is shown.

\begin{array}{lcl} finish & = & distance \times pace \\ t_{2} & = & t_{1} \times {(\frac{d_{2}}{d_{1}})}^{p} \\ M & = & 326.3 + 2.394 K - 12.06 V - 46.1 R \\ elapsed & = & moving \times (1 + \frac{a}{100}) + stops \end{array}

The variables in those equations map to practical race inputs. Distances may be entered in kilometres or miles, with one mile treated as 1.609344 kilometres. Marathon distance is 42.195 km and half marathon distance is 21.0975 km in the standard presets.

Race pace suite variable meanings
Symbol or field	Meaning	Unit or range
`t1`, `d1`	Previous race time and previous race distance	Seconds and metres
`t2`, `d2`	Predicted target time and target race distance	Seconds and metres
`p`	Riegel exponent used for distance fade	0.90 to 1.20
`K`	Weekly running distance used by the training estimate	km/week
`V`	Average training speed used by the training estimate	km/h
`R`	Runs per week used by the training estimate	Whole runs/week
`a`	Finish adjustment for weather, course difficulty, calibration, or conservative planning	Percent

After the base clock is known, the elapsed finish adds assumptions. A positive finish adjustment slows the moving estimate, a negative adjustment speeds it up, and planned stops add race-clock time. The split ladder then divides the adjusted race into kilometre or mile checkpoints. The displayed split pace is gross pace for that segment, so a planned stop inside a segment makes that segment look slower.

Race pace suite calculation paths and validation boundaries
Path	Required evidence	Important boundary
Plan from target pace or speed	Positive distance plus pace, speed, or finish time	Wrong kilometres versus miles changes every pace and split value.
Predict from a recent race	Previous race distance, previous race time, target distance, and exponent	Reference-to-target distance ratio drives the `Prediction caution` label.
Estimate marathon from training	Weekly running distance, average training speed, and runs per week	A non-positive model result is rejected, and very fast outputs need a sanity check against training speed.
Split ladder and scenarios	Any positive finish estimate	The split unit changes checkpoints, not total race distance.

Everyday Use & Decision Guide:

Start with Planning mode. Use Plan from target pace or speed when you already know the goal, such as 5:00 per kilometre for 10 km or 12.0 km/h on a treadmill. Use Predict from a recent race when a verified race is your best evidence. Use Estimate marathon from training for a rough marathon check from a normal training block.

Keep the first pass simple. Set the race distance, confirm kilometres or miles, leave Finish adjustment at 0%, and leave planned stops at 0 until the neutral baseline looks right. Then change one assumption at a time, such as a +5% course stress allowance, a late-fade pacing profile, or a short stop budget for aid stations.

The most common bad output comes from a good number in the wrong unit. A pace entered as 8:00 per kilometre is much slower than 8:00 per mile. The Average pace, Average speed, and Target distance rows in Pace Plan Brief are the fastest way to catch that mistake before using the split table.

For direct pacing, trust the arithmetic only after the Projected finish and both pace units match your race plan.
For race prediction, slow down when Prediction caution says Wide-distance stretch.
For marathon training, compare Race speed vs training speed before treating the estimate as a goal.
For planned stops, remember that the split containing the stop includes the pause because the race clock keeps running.

A result is useful when it changes a race decision. If the scenario guide moves the finish by several minutes, build the plan around a range. If all scenarios cluster tightly, the current target is less sensitive to the assumptions being tested.

Step-by-Step Guide:

Follow the branch that matches the evidence you trust most, then read the brief before using the detailed tables.

Set Planning mode to the path you need. The summary badge changes to Pace plan, Riegel prediction, or Training model.
For direct pacing, choose Race distance and set Target input to Pace, Speed, or Finish time. Check that the large summary finish and Average pace row match the intended unit.
For recent-race prediction, enter Previous race distance, Previous race time, and Target race distance. Review Prediction caution before using the target as a race goal.
For the marathon training estimate, enter Weekly running distance, Average training speed, and Runs per week. If Race speed vs training speed is very high, treat the result as a rough model output rather than a pacing promise.
Choose Split ladder unit as 1 kilometre or 1 mile so Race Split Ladder matches course markers, watch alerts, or crew notes.
Open Advanced only after the neutral result is sensible. Add Pacing profile, Finish adjustment, Planned stops, Stop placement, or Riegel exponent changes one at a time.
If the warning says to enter a positive race distance and valid time, pace, speed, or training profile, fix the primary inputs first. Results appear only after the inputs produce a positive finish time.
Read Pace Plan Brief, then move to Race Split Ladder, Adjustment Scenario Guide, Pace Band Ladder, or the chart tabs depending on whether you need checkpoints, sensitivity, pace offsets, or visual timing shape.

Interpreting Results:

Projected finish is the elapsed race time after finish adjustment and planned stops. Neutral baseline is the base moving estimate before those additions. When those values differ, the gap is not mysterious fitness gain or loss; it comes from the adjustment percent, stop budget, or both.

Average pace is gross race pace. It includes planned stop time and therefore may be slower than the pace you expect to see while actively running. Use Race Split Ladder for checkpoint planning, but use the segment notes to notice where a stop has been inserted.

Race prediction confidence changes with distance stretch. The same Riegel exponent can be useful for nearby distances and much shakier for a jump from a short race to a marathon.

Prediction caution label boundaries
Prediction caution	Reference-to-target distance ratio	How to read it
`Close-distance comparison`	< 1.8	Usually the most defensible use of a recent race result.
`Moderate stretch`	≥ 1.8 and < 4.0	Useful as a planning estimate, but check race specificity and conditions.
`Wide-distance stretch`	≥ 4.0	Treat the finish as a broad range unless other evidence supports it.

A fast result does not mean the goal is safe. Check the Scenario Finish Chart, the pace-band rows, and the mode-specific caution fields. If a small exponent change, a +5% race-day adjustment, or one extra weekly run changes the result enough to alter the plan, the honest output is a range.

Worked Examples:

A 10 km target pace becomes a pacing sheet

A runner chooses Plan from target pace or speed, sets Race distance to 10 km, and enters 5:00 per kilometre. Projected finish is 50:00, Average pace shows 5:00 /km | 8:03 /mile, and the kilometre split ladder has ten checkpoints. With no adjustment and no planned stops, Neutral baseline also reads 50:00.

A 10 km result predicts a half marathon

A recent 50:00 10 km result is entered in Predict from a recent race with Target race distance set to half marathon and Riegel exponent at 1.06. Projected finish is about 1:50:19, with average pace near 5:14 /km | 8:25 /mile. Because the half marathon is just over twice the reference distance, Prediction caution reads Moderate stretch, so the estimate should be checked against endurance training and race conditions.

A training estimate needs a sanity check

A marathon estimate from 55 km/week, 9.0 km/h, and 3 runs per week produces about 3:31:08, or roughly 5:00 /km. Changing only Runs per week to 4 moves the model near 2:45:02. That large jump is a warning to inspect Race speed vs training speed and compare the result with recent long runs before using it as a race target.

A planned stop changes one split

A 10 km plan at 50:00 with one 30-second planned stop finishes at 50:30. If the stop lands inside a kilometre segment, that row in Race Split Ladder includes the pause and its Split pace looks slower than the moving effort. The result is useful for race-clock checkpoints, not for judging running form during the stop.

FAQ:

Which planning mode should I use first?

Use Plan from target pace or speed when you already know the target. Use Predict from a recent race when a verified finish time is your strongest evidence. Use Estimate marathon from training when you want a rough marathon check from weekly distance, training speed, and run frequency.

Why does the same finish show different pace units?

Average pace reports both kilometres and miles from the same elapsed finish. One mile is treated as 1.609344 kilometres, so 5:00 /km becomes about 8:03 /mile.

Why does a planned stop make a split slower?

The split table uses elapsed race time. If stop time is placed inside a segment, the pause is included in that segment's Segment time and Split pace.

Why does a race prediction show a caution label?

Prediction caution compares the larger race distance with the smaller one. A ratio below 1.8 is close, a ratio below 4.0 is moderate, and anything wider is marked as a wide-distance stretch.

What should I do when the page shows the yellow input warning?

Fix the primary numbers first. The warning appears when the selected path does not produce a positive finish time from the race distance and valid time, pace, speed, or training profile.

Does the calculator upload my race data?

The race calculations run in the browser from the values on the page. The tool does not send those race inputs to a dedicated prediction service for processing.

Glossary:

Race pace: The time needed to cover one kilometre or one mile at the planned average speed.
Gross pace: Average pace across elapsed race time, including planned stop time when stops are included.
Neutral baseline: The base finish estimate before finish adjustment and planned stop time are added.
Riegel exponent: The power value that controls how much predicted pace slows as target distance grows.
Finish adjustment: A percentage change applied to the moving estimate for weather, course difficulty, calibration, or conservative planning.
Split ladder: The kilometre or mile checkpoint table that shows segment time and cumulative race-clock time.
Prediction caution: The label that flags whether the previous race and target race are close, moderate, or widely separated by distance.

References:

The Measurement of Road Race Courses, World Athletics and AIMS, 2023.
U.S. Survey Foot: Revised Unit Conversion Factors, National Institute of Standards and Technology, updated February 3, 2026.
An empirical study of race times in recreational endurance runners, BMC Sports Science, Medicine and Rehabilitation, 2016.
Prediction of marathon performance time on the basis of training indices, Journal of Human Sport and Exercise, 2011.