Pace & Speed Converter
Convert running pace to speed or speed to pace, then estimate finish times, split checkpoints, and Riegel race projections in km or miles.Pace-Speed Conversion
Current result
| 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.
|
||||||
Introduction
Race plans, treadmill consoles, GPS watches, and coaching notes often describe the same running effort in different languages. Pace writes the effort as time per distance, such as 5:00 / km or 8:03 / mile. Speed writes it as distance per hour, such as 12.00 km/h or 7.46 mph. Both are correct, but they move in opposite directions: a faster runner has a smaller pace number and a larger speed number.
That reciprocal relationship is why pace-speed conversion is easier to misread than a normal unit switch. Changing from kilometres to miles changes the distance basis, not just the label. A five-minute kilometre is a strong recreational pace; a five-minute mile is a much faster racing pace. The same problem appears on treadmills when 12 km/h is accidentally treated like 12 mph.
| Term | Plain meaning | Where runners use it |
|---|---|---|
| Pace | Elapsed time needed to cover one kilometre or one mile. | Workout targets, race splits, coaching plans, and watch alerts. |
| Speed | Distance covered in one hour at the same average effort. | Treadmills, multi-sport displays, and some training logs. |
| Finish time | Average pace multiplied by a chosen race or route distance. | Checking a 5K, 10K, half marathon, marathon, or custom goal. |
| Projection | An estimate of how a reference effort may translate to another distance. | Comparing a recent race with a longer or shorter target event. |
Distance is what turns a rate into a plan. A 5:00 / km pace by itself describes a running effort. Over 10 km, it becomes a 50:00 finish time. Broken into one-kilometre checkpoints, it becomes a split sheet. Compared with a half-marathon goal, it becomes a projection that needs more judgment because the event length has changed.
Even-pacing math is exact once the chosen rate and distance are fixed, but race planning rarely stays that neat. Hills, weather, surface, turns, crowding, watch error, fatigue, and fueling all affect the real clock. A conversion can tell you what a steady effort means; it cannot prove that the effort will feel the same at every point in a race.
Race projections add one more assumption. They compare a reference performance with another distance using an endurance exponent, so a 10K result can be turned into a half-marathon estimate without pretending the same pace carries unchanged. The estimate is useful for setting expectations, but it is most trustworthy when the reference run and target race are similar in distance, conditions, and training demand.
How to Use This Tool:
Start from the number you trust, then add distance only when you want finish-time, split, or race-projection outputs.
- Choose whether you are entering Pace or Speed. Use pace for minutes and seconds per kilometre or mile, and speed for treadmill-style values such as
12.0 km/hor7.5 mph. - Select the road unit that matches the entry. The pace unit and speed unit stay aligned, so kilometre pace pairs with
km/hand mile pace pairs withmph. - Check Effort Snapshot and Conversion Table first. They show the primary pace, alternate pace, primary speed, and alternate speed for the same effort.
If the validation message asks for a pace or speed, enter a value above zero before using the result tabs.
- Open Advanced and set Distance when you need a finish time, course markers, split ladder, or race projection. Leaving distance at
0keeps the page in conversion-only mode. - Set Split distance to the checkpoint you will actually follow, such as
1 km,1 mi, or400 m.Very small split sizes can create a dense ladder. The table stops at a bounded checkpoint count so the result stays readable. - Choose a Projection profile only after the base rate and distance are correct. Balanced uses Riegel
1.06, Endurance-leaning uses1.04, and Speed-leaning uses1.08. - Use Race Projection Ladder and Goal stretch as planning checks, then copy or download the JSON only when the selected units, distance, split size, and profile match the run you meant to model.
Interpreting Results:
Pace and Speed are the core conversion results. They are arithmetic equivalents, so they should agree with each other even when the chosen unit system changes. If a result feels surprising, check the distance unit before changing the number.
- Finish time assumes the selected average pace holds across the full distance.
- Course Markers gives quarter, halfway, three-quarter, and final-unit timing cues when they fit inside the route.
- Split Ladder shows segment time, cumulative time, remaining time, and progress for the selected checkpoint size.
- Race Projection Ladder estimates standard race distances and a custom goal distance from the selected Riegel profile.
- Pace-Speed Map places the current effort on an inverse rate curve with nearby faster and slower regions.
Treat direct conversions as rate facts and projections as training assumptions. A near-reference projection, such as 10K to 5K or 10K to 10 miles, usually asks less of the model than a short run projected to a marathon. When Goal stretch reads moderate or high, use the projected time as a rough range marker rather than a race promise.
Technical Details:
Pace and speed are reciprocal rates. The calculation normalizes the effort to seconds per kilometre, then derives seconds per mile, kilometres per hour, and miles per hour from that base. This keeps a pace entry and a speed entry consistent even when the visible unit changes.
Finish-time calculations are linear. If pace stays fixed, doubling distance doubles elapsed time. Race projections are not linear because fatigue, economy, and event demands change with distance. The projection uses a power-law form associated with Peter Riegel's race-time model, with selectable exponents that make the estimate more endurance-leaning or more conservative.
Formula Core:
| Item | Value or rule | Why it matters |
|---|---|---|
| Mile conversion | 1 mi = 1.609344 km |
Used for mile pace, miles per hour, mile distances, and metre split conversion. |
| Standard projection distances | 5K, 10K, 10 miles, half marathon, marathon, and custom goal |
Gives a consistent race-equivalence ladder once a reference distance is set. |
| Projection exponents | 1.04, 1.06, 1.08 |
Lower values preserve pace more strongly; higher values add more slowdown as distance grows. |
| Goal stretch | High at >= 1.75 or <= 0.55; moderate at >= 1.25 or <= 0.8 |
Flags projections where the goal distance is far from the reference distance. |
| Split ladder size | Up to 500 intermediate checkpoints plus finish |
Keeps very small checkpoint choices from producing an unbounded table. |
A 5:00 / km pace equals 300 seconds per kilometre. The matching speed is 3600 / 300 = 12.00 km/h. Over 10 km, the even-pace finish is 300 x 10 = 3000 seconds, or 50:00. With the balanced exponent, a half-marathon projection from that 10K reference is 3000 x (21.0975 / 10)^1.06, which rounds to about 1:50:19.
Displayed times are rounded to whole seconds, and displayed speeds are rounded to readable decimals. Small differences can appear when a rounded pace was derived from a more exact speed entry, especially near boundaries such as 4:58 / km versus 4:59 / km.
Limitations:
The conversion rows are deterministic, but the planning rows depend on running assumptions. Even pace, clear distance measurement, and comparable race conditions are simplifications.
- Hills, wind, heat, altitude, turns, surface, congestion, and GPS drift can change real splits.
- Projection rows do not measure current fitness, injury risk, recovery, fueling, or late-race durability.
- Very short checkpoints can help on a track or treadmill, but road watches may not measure them cleanly.
- Data is calculated in the browser after the page loads; no server lookup or file upload is needed for pace, split, chart, or JSON results.
Worked Examples:
Convert a 50-minute 10K plan
Enter 5 minutes and 0 seconds for pace, keep the unit on kilometres, and set Distance to 10 km. The speed is 12.00 km/h, the alternate pace is about 8:03 / mile, and the finish time is 50:00. A one-kilometre split ladder shows 5:00 segments.
Turn treadmill speed into mile pace
Choose speed entry, set the unit to miles, and enter 7.5 mph. The matching pace is about 8:00 / mile, and the alternate pace is about 4:58 / km. If the distance is 5 mi, the even-pace finish is 40:00.
Compare a 10K result with a half-marathon goal
A 50:00 10K reference with the balanced profile projects the half marathon near 1:50:19. Switching to Endurance-leaning makes the estimate faster, while Speed-leaning makes it slower. The spread is useful because a longer race tests endurance and fueling, not just the 10K pace.
Fix a blank result
If both pace and speed are blank or zero, the page asks for a valid rate. Enter either pace, such as 5:00, or speed, such as 12.0 km/h. The summary, conversion table, and optional planning rows return as soon as one valid rate exists.
FAQ:
Should I enter pace or speed?
Enter whichever value came from your source. Use pace for a training plan, race result, or split target. Use speed for a treadmill, bike-style display, or log that records distance per hour.
Why did switching kilometres and miles change the result?
The unit switch changes what the pace number means. 5:00 / km and 5:00 / mile are both valid entries, but they describe very different running speeds.
Does split distance change finish time?
No. Split distance only changes checkpoint spacing. Finish time still comes from average pace multiplied by the total distance.
Which projection profile should I use?
Use Balanced for the middle estimate. Use Endurance-leaning when your longer races usually hold up well, and Speed-leaning when you want a more conservative slowdown estimate.
Why are shorter races included in the projection table?
The ladder compares the same reference effort across standard distances. Shorter targets can still differ from a direct conversion because the Riegel exponent changes projected pace with distance.
Glossary:
- Pace
- Time per unit distance, usually minutes per kilometre or minutes per mile.
- Speed
- Distance covered per hour, usually kilometres per hour or miles per hour.
- Split
- A checkpoint interval inside a run, such as each kilometre, mile, or 400 metres.
- Reference distance
- The distance tied to the current rate before projecting to another race length.
- Riegel exponent
- The power-law value used to estimate how race time changes when distance changes.
- Goal stretch
- The custom goal distance compared with the reference distance.
References:
- Handbook 44 Appendix C, General Tables of Units of Measurement, National Institute of Standards and Technology, 2023.
- The Measurement of Road Race Courses, World Athletics and AIMS, 2023.
- Athletic Records and Human Endurance, Peter S. Riegel, American Scientist, 1981.