Pace & Speed Converter

Pace-Speed Conversion

{{ paceReadable || '—' }} = {{ speedReadable || '—' }}

Pace:

Format is minutes + seconds, e.g. 5 and 00 for 5:00 per selected road unit.

Speed:

Use values such as 12.0 km/h or 7.5 mph; unit selection syncs the pace basis.

Distance:

Enter race or session distance in the active road unit; 0 hides planning rows.

Split distance:

Use 1 km/mi for race splits or 400 m for track-style checkpoints; minimum 0.01.

Projection profile:

Balanced 1.06, endurance 1.04, speed 1.08; compare profiles when distance changes.

Goal distance:

Enter a positive race distance, for example 21.0975 km or 13.1 mi.

View	Current	Notes	Copy
{{ row.label }}	{{ row.current }}	{{ row.notes }}

Metric	Value	Copy
{{ row.label }}	{{ row.value }}

Marker	Clock	Remaining	Copy
{{ marker.label }}	{{ marker.clock }}	{{ marker.remaining }}

Topic	Details	Copy
{{ note.title }}	{{ note.text }}

Checkpoint	Distance	Split Time	Cumulative	Remaining	Progress	Copy
{{ s.label }}	{{ s.splitDistance }}	{{ s.splitTime }}	{{ s.cumulativeTime }}	{{ s.remainingTime }}	{{ s.progress }}
No split ladder yet Add a distance and keep a valid pace or speed input to build the pacing ladder.

Race	Distance	Projected Time	Projected Pace	Projected Speed	Vs Current Pace	Copy
{{ row.race }}	{{ row.distance }}	{{ row.projectedTime }}	{{ row.pace }}	{{ row.speed }}	{{ row.paceDelta }}
No projection ladder yet Add a distance to generate equivalent race projections from the current pace-speed conversion.

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Running pace and running speed describe the same effort from opposite directions. Pace asks how long one kilometre or mile takes. Speed asks how many kilometres or miles fit into one hour. Switching between those views is common when a road plan uses min/km or min/mi but a treadmill, bike display, or training log shows km/h or mph.

A useful conversion also needs distance context. A pace of 05:00 / km is just a rate until it is tied to 5 km, 10 km, a half marathon, a marathon, or a custom route. With a distance entered, the same effort becomes a finish time, course markers, a split ladder, and distance-based race estimates.

Pace and speed curve with the current effort between easy running and race-push effort

The direct conversions and finish-time rows are arithmetic. Race projections are estimates from a distance model, so they are best read as planning ranges, especially when the goal race is much shorter or much longer than the reference effort.

How to Use This Tool:

Start with the measurement you trust most, then add only the race or workout context you need.

Enter either Pace or Speed. Road plans usually start with pace, while treadmills often start with speed.
Choose the active unit system. Use kilometres for min/km and km/h, or miles for min/mi and mph.
Add Distance when you want a finish time, course markers, split rows, and race projections. Leave it blank when you only need conversion.
Set Split distance to match the feedback you expect during the run. 1 km and 1 mi suit road pacing; metre-based splits suit shorter repeats.
Pick a projection profile only after the base pace and finish time look right. Endurance assumes less slowdown over longer races, Balanced uses the common middle exponent, and Speed assumes more slowdown as distance increases.
Review Effort Snapshot and Conversion Table first, then move to Course Markers, Split Ladder, Race Projection Ladder, and Pace-Speed Map.

If the result looks wrong, check the pace unit before changing the number. A valid 05:00 / km effort and a valid 05:00 / mi effort are very different speeds.

Interpreting Results:

Pace per km, Pace per mile, Speed km/h, and Speed mph are equivalent statements of one average effort. When distance is blank, these conversion fields are the main result.

Finish time assumes the same average pace holds for the full selected distance.
Course Markers show broad checkpoints such as quarter, halfway, three-quarter, and late-race cues when the distance supports them.
Split Ladder lists repeated checkpoints with split time, cumulative time, remaining time, and progress percentage.
Race Projection Ladder applies the selected distance exponent to estimate how the reference effort may translate to other race lengths.
Pace-Speed Map places the current effort among nearby faster and slower ranges for a visual sanity check.

Treat projection rows with more caution than conversion rows. A 10 km time can give useful half-marathon context, but a marathon estimate also depends on durability, fueling, weather, elevation, and pacing discipline.

Technical Details:

Pace is time divided by distance, and speed is distance divided by time. The reciprocal relationship means a faster pace has a smaller time value, while a faster speed has a larger distance-per-hour value. The calculation normalizes every entry to seconds per kilometre, then derives the mile view and speed views from that shared value.

Race distance estimates use a power-law relationship. The reference time is scaled by the ratio between goal distance and reference distance, raised to an exponent. The classic Riegel form is often written as T2 = T1 × (D2 / D1)^1.06. The selectable profiles keep that middle value and add lower and higher exponents so runners can see how sensitive longer targets are to assumed endurance.

Formula Core:

The core equations keep pace, speed, finish time, and projection math tied to one normalized effort.

v_{km/h} = \frac{3600}{p_{km}} p_{km} = \frac{3600}{v_{km/h}} T_{finish} = p_{km} \times D_{km} T_{goal} = T_{ref} \times {(\frac{D_{goal}}{D_{ref}})}^{e}

Pace and speed symbol definitions
Symbol or value	Meaning
`p_km`	Pace in seconds per kilometre.
`v_km/h`	Speed in kilometres per hour.
`D`	Distance after conversion to kilometres. One international mile is exactly `1.609344 km`.
`e`	Projection exponent: `1.04` endurance, `1.06` balanced, or `1.08` speed-leaning.

For a 05:00 / km reference, p_km is 300 seconds. The speed is 3600 / 300 = 12.00 km/h. Over 10 km, finish time is 300 × 10 = 3000 seconds, or 00:50:00. A balanced projection from that 10 km reference to a half marathon uses 3000 × (21.0975 / 10)^1.06, which lands near 01:50:19.

Road distance and projection rules used by the calculator
Rule	Value	Why it matters
Mile conversion	`1 mi = 1.609344 km`	Keeps mile pace, kilometre pace, `mph`, and `km/h` consistent.
Half marathon	`21.0975 km`	Uses half of the official marathon distance rather than a rounded `21.1 km` label.
Marathon	`42.195 km`	Matches the standard road-race distance used by World Athletics.
Projection profile	`1.04`, `1.06`, or `1.08`	Shows how strongly assumed endurance changes longer-distance estimates.

Rounding is for display, not for changing the underlying effort. Time values are shown as readable clock strings, speeds are rounded to practical decimals, and split rows are capped so very small intervals do not overwhelm the page.

Limitations:

Even pacing is an assumption, not a race plan. The calculator does not model hills, wind, heat, altitude, crowded starts, water stops, GPS drift, terrain changes, footwear, or fatigue late in a race.

The Riegel projection is a distance-based estimate, not a personal physiology model. It cannot know recent training load, long-run history, injury risk, fueling practice, or how well a runner holds pace after the reference distance. Estimates become less reliable when the goal distance is far from the reference performance.

Use the results to compare rates, build checkpoint sheets, and test target plausibility. Race-day decisions still need current fitness, course conditions, and recovery status.

Worked Examples:

Convert a 10 km goal pace into finish time and checkpoints

Enter 05:00 / km and set distance to 10 km. The matching speed is 12.00 km/h, the finish time is 00:50:00, and the broad markers land at 00:12:30, 00:25:00, 00:37:30, and 00:45:00 for the start of the final kilometre.

Start with treadmill speed and read the road pace

Enter 7.5 mph. The equivalent pace is 08:00 / mile, about 04:58 / km, and the matching metric speed is about 12.07 km/h. With a 5 mi distance, the even-effort finish time is 00:40:00.

Compare projection sensitivity from a 50-minute 10 km

A 10 km result of 00:50:00 projects to roughly 01:48:41 for a half marathon with the endurance profile, about 01:50:19 with the balanced profile, and about 01:51:59 with the speed-leaning profile. The spread is the useful signal: a longer goal race should be planned with margin, not treated as one exact clock.

FAQ:

Should I enter pace or speed?

Enter the value you measured or plan to use. Pace is usually better for road running and racing. Speed is often better when copying a treadmill setting.

Why did my result change so much after switching from kilometres to miles?

The unit changed the meaning of the pace entry. Five minutes per kilometre is not the same effort as five minutes per mile. Check the active unit before trusting the conversion.

Does split distance change the finish time?

No. Split distance only changes the checkpoint spacing. The finish time still comes from average pace multiplied by total distance.

Which projection profile should I use?

Use balanced when you want the common middle estimate. Use endurance when your training supports longer distances well. Use speed-leaning when the goal race is longer than your reference effort and you want a more conservative slowdown assumption.

Why are marathon projections more uncertain than 5K or 10K projections?

Marathon performance depends heavily on long-run durability, fueling, weather, pacing discipline, and late-race fatigue. A distance-only model cannot measure those factors.

Does my data leave the browser?

No. The pace conversion, chart, downloadable files, and JSON output are generated in the browser after the page loads.

Glossary:

Average pace: Time per unit distance, usually written as minutes per kilometre or minutes per mile.
Speed: Distance per hour, usually shown as kilometres per hour or miles per hour.
Split: A checkpoint interval inside a longer run, such as every kilometre, mile, or 400 metres.
Reference distance: The distance tied to the current pace or finish time before projecting to another race length.
Riegel exponent: The power-law value used to scale a known race time to another distance.

References:

Handbook 44 Appendix C, General Tables of Units of Measurement, National Institute of Standards and Technology.
Marathon, World Athletics.
Terms and abbreviations, World Athletics.
Athletic Records and Human Endurance, Peter S. Riegel, American Scientist, 1981.