Calculate running pace, finish time, or distance
Any running calculation involves three variables: pace (time per kilometre or mile), time (total duration of the run), and distance (total kilometres or miles). If you know two of these, you can always calculate the third:
Pace = Time ÷ Distance
Time = Pace × Distance
Distance = Time ÷ Pace
A runner who covers 10 km in 55 minutes has a pace of 5:30 per km. At that same pace, a half marathon (21.097 km) would take 5:30 × 21.097 ≈ 1:56:02.
| Race | Distance | At 5:00/km | At 6:00/km | At 7:00/km |
|---|---|---|---|---|
| 5K | 5.0 km | 25:00 | 30:00 | 35:00 |
| 10K | 10.0 km | 50:00 | 60:00 | 70:00 |
| Half marathon | 21.1 km | 1:45:33 | 2:06:36 | 2:27:42 |
| Marathon | 42.2 km | 3:31:00 | 4:13:12 | 4:55:24 |
Different training paces produce different physiological adaptations. Most training plans use 5–6 distinct pace zones:
| Zone | Description | Feel | Purpose |
|---|---|---|---|
| Easy / recovery | 60–65% max HR | Comfortable conversation | Recovery, aerobic base |
| Aerobic | 65–75% max HR | Can speak in sentences | Endurance building |
| Tempo | 80–87% max HR | Comfortably hard | Lactate threshold |
| Threshold | 87–92% max HR | Can say a few words | Race pace fitness |
| VO2 max | 92–97% max HR | Hard, 3–8 min efforts | Maximum aerobic capacity |
Research by exercise physiologist Stephen Seiler shows that elite endurance athletes typically do approximately 80% of their training at easy to moderate intensity and only 20% at high intensity. Most recreational runners do the opposite — running too hard on easy days and not hard enough on hard days. The result is chronic fatigue, inadequate recovery, and slower progress than the easy 80% approach would produce.
It depends entirely on your fitness level and experience. For a beginner, completing a 5K at any pace is an achievement. For reference, average recreational runners complete a 5K in 30–35 minutes (6:00–7:00 per km), a 10K in 60–75 minutes, and a half marathon in 2:15–2:45. Elite marathon runners run at under 3:00/km; typical club runners at 4:30–5:30/km.
To convert min/km to min/mile: multiply by 1.60934. A 5:00/km pace equals 8:03/mile. To convert min/mile to min/km: divide by 1.60934. A 10:00/mile pace equals 6:13/km.
A rough prediction: multiply your 10K time by 4.65 for a marathon estimate. More accurate predictions use formulas like Riegel's: T2 = T1 × (D2/D1)^1.06, where T1 and D1 are your known time and distance and T2/D2 are the target. This accounts for the increasing difficulty at longer distances.
Easy runs should feel genuinely easy — you should be able to hold a full conversation without breathing hard. For most runners this is 1–2 minutes per km slower than your 10K race pace. Many runners run their easy days far too fast, accumulating fatigue without the recovery benefit of truly easy effort.
Performance degrades significantly with temperature. For every 1°C above 15°C, pace slows by approximately 0.3–0.5% for most runners. In temperatures above 25°C, expect 5–8% slowdown; above 30°C, 10–15% or more. Adjust expected pace and hydration strategy accordingly for warm-weather running.