Pace is the runner's native unit — not how fast you are going, but how long each kilometer or mile is taking you — and every race plan is built from it. This calculator solves the pace triangle in all directions: pace from time and distance, finish time from pace and distance, distance from time and pace, and the required pace for a goal — with speed conversions included.
The Core Relationship
Work in kilometers or miles; the calculator converts between them (1 mile = 1.60934 km) and also reports speed — pace's reciprocal view: , so a 300-second kilometer is 12 km/h.
| Mode | You enter | You get | | --- | --- | --- | | Pace | Time + distance | Pace per km and per mile, speed in km/h and mph | | Time | Pace + distance | Projected finish time | | Distance | Time + pace | Distance covered | | Goal | Goal time + race distance | Required pace per km and per mile, and speed |
Worked Examples
The 4-hour marathon. 240 minutes over 42.195 km requires 5:41 per km — equivalently 9:09 per mile — at a steady 10.55 km/h. Those two numbers, taped to a wrist or programmed into a watch, are the entire race plan; the goal mode exists to produce them for any target: halve the distance and the same pace yields a 2:00 half marathon, which is why "sub-2 half, sub-4 full" is one fitness level wearing two shirts.
Finish-time projection. Training comfortably at 5:30/km, a 10K takes 5.5 × 10 = 55:00 — enter it in time mode before race day rather than discovering it at kilometer 8.
Treadmill translation. Treadmills speak speed; runners think pace. 10 km/h = 6:00/km, and 6 mph = 10:00/mile — the conversions the pace mode's speed outputs hand you directly.
Racing and Training with the Numbers
A calculator pace is an average over the whole distance, and real races are not run at metronome evenness: crowds, hills, aid stations, and honest fatigue all bend the split pattern. Plan around it — aim for even or slightly negative splits (second half at or a touch faster than the first), bank no time in the opening kilometers when everything feels easy, and on hilly courses judge effort by the average at each checkpoint rather than chasing the target pace up every climb. For training, the same math builds sessions: if your goal marathon pace is 5:41/km, tempo work lives near it, intervals run meaningfully faster (a 5K-pace repetition might be ~5:00/km), and easy days run 60–90 seconds per km slower — the calculator converts any of those targets into the per-lap or per-rep times a track session needs (a 400 m rep at 5:00/km pace is 2:00 exactly). Standard distances for goal-setting: 5K = 3.107 mi, 10K = 6.214 mi, half marathon = 21.0975 km / 13.109 mi, marathon = 42.195 km / 26.219 mi.
Limitations
The math assumes constant pace and ignores elevation, wind, temperature, and fatigue, all of which move real finish times — treat projections as the flat-course, good-day figure and pad accordingly. GPS watches also measure distance imperfectly (a "marathon" on a watch often reads 42.5+ km through city streets), so pace-by-watch and pace-by-course-markers can disagree slightly without either being wrong.
Frequently Asked Questions
What is the difference between pace and speed?
They are reciprocals describing the same motion: speed is distance per time (km/h, mph), pace is time per distance (min/km, min/mi). Runners plan in pace because race targets are stated as times over known distances; treadmills and cyclists default to speed — this calculator reports both so you never convert by hand.
How do I convert min/mile to min/km?
Divide by 1.60934: an 8:00 mile is 480 ÷ 1.60934 ≈ 298 seconds ≈ 4:58/km. Going the other way, multiply by 1.60934. The calculator's dual outputs exist because mixed-unit races and imported training plans make this conversion a weekly chore.
What pace do I need for a sub-30-minute 5K?
Six minutes per kilometer exactly: 30 ÷ 5 = 6:00/km (about 9:39/mile). Enter any goal in goal mode — time plus distance — and it returns the required pace per km, per mile, and the equivalent speed.