Your running pace (time per kilometer) is the basic number for managing training intensity and setting race goals. Enter any two of distance, time and pace and this tool calculates the third, along with projected times for common race distances (5K, 10K, half, full) and per-kilometer splits.
How to use this tool
Choose what to solve for, then fill in the other two values. For example, to find your pace after running 10 km in 55 minutes, select "Pace" and enter distance 10 and time 55 minutes. To work backwards from a goal, select "Pace" and enter your target race time and distance to see the per-km pace you need.
Reading the projections
Projected times assume you hold exactly the same pace to the finish. In real races pace drops as distance grows, so predictions from shorter races use conversion formulas such as Riegel's formula. Treat the values here as guides for setting training paces.
Tips
Pairing pace with heart-rate control keeps intensity consistent (Heart Rate Zone Calculator). Check calories burned with the Calories Burned Calculator and hydration with the Water Intake Calculator.
What is the difference between pace and speed?+
Runners usually talk in pace. Examples: 5:00/km pace = 12 km/h, 6:00/km = 10 km/h. This tool shows both.
What pace do I need for a sub-4 or sub-3 marathon?+
Because of water stops and course conditions, most runners target a pace a few seconds faster than these.
How reliable are the projected times?+
Since pace drops as distance grows, projecting a long race from a short one gives an optimistic value. For race predictions, also consider Riegel’s formula (T2 = T1 × (D2/D1)^1.06).
What pace should I train at?+
Easy runs (conversational): 1–2 min/km slower than race pace
Tempo runs: around race pace
Intervals: faster than race pace, over short distances
Combining pace with heart-rate zones (Zones 2–4) makes intensity easier to manage.
Can I convert this to a treadmill speed?+
Since there is no wind resistance indoors, setting a 1% incline is commonly said to approximate outdoor effort.
・Formula: pace (sec/km) = time (sec) ÷ distance (km). Projections are simple same-pace conversions.
・Riegel PS. (1981). Athletic Records and Human Endurance. American Scientist, 69(3), 285–290.
Projected times are simple conversions assuming a constant pace and do not guarantee race results. Conditions, course and how you feel on the day all matter. Choose sustainable paces and stop immediately if you feel unwell.
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