Planning a race time, pace target, or just figuring out what speed you actually ran your last 5K? This calculator handles all three running questions: enter distance + time, get pace (minutes per mile or km) and speed (mph, km/h). Quick preset buttons for 5K, 10K, half marathon, and full marathon distances. Use it to plan race goals ("if I want to break 4 hours in the marathon, my average pace needs to be 9:09/mile"), set training paces, or just convert between mile and km units.
Pace
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Per km
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Per mile
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Speed (mph)
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Speed (km/h)
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Race distance presets
Pace targets for common race goals
Race goal
Min/mile
Min/km
5K under 30 min
9:39
6:00
5K under 25 min
8:03
5:00
5K under 20 min
6:26
4:00
10K under 1 hour
9:39
6:00
10K under 45 min
7:14
4:30
Half marathon under 2 hr
9:09
5:41
Half marathon under 1:45
8:00
4:58
Marathon under 4 hr (BQ for older)
9:09
5:41
Marathon under 3:30
8:00
4:58
Marathon under 3 hr (BQ for men under 35)
6:52
4:16
How to use this calculator
Distance + unit: in miles or kilometers. Use presets for common race distances.
Finish time: hours, minutes, seconds.
Output: pace in min/km AND min/mile, speed in mph and km/h.
For pace-based planning: pick a target finish time and distance, see what pace you need to maintain.
For workout planning: set distance + pace by working backward from your typical interval times.
Common scenarios
5K finished in 25:00. Pace 8:03/mi (5:00/km). Speed 7.5 mph (12 km/h). Solid recreational runner pace.
Half marathon goal of sub-2 hours. Needs 9:09/mi average (5:41/km). Train at 8:30-9:00 pace for long runs to have margin on race day.
Marathon goal of 3:30 (BQ for women under 35). 8:00/mi pace (4:58/km). Demands serious training: 50+ mile weeks for 12-16 weeks, with marathon-pace long runs.
FAQ
What's a good 5K time? +
For recreational adult runners: 28-32 min is solid. Under 25 min puts you in the top 15-20% of recreational racers. Under 20 min is competitive amateur territory. Sub-15 min is elite. Most healthy adults can train down to ~30 min in 6-12 months.
What's a Boston Marathon qualifying time? +
Varies by age and gender. For 2024-2025 standards: Men 18-34 = 3:00:00; Men 35-39 = 3:05:00; Women 18-34 = 3:30:00. Time gets more generous (slower) with age. Field is competitive — you typically need to beat the qualifying time by 1-3 minutes to actually get a slot.
How long until I see pace improvement? +
For new runners: dramatic improvement in 8-12 weeks (5K time drops by 3-5 min). For intermediate runners (already running 12+ months): 5-10 sec/mile per training cycle. For experienced runners: 1-3 sec/mile per year. Bigger gains require bigger volume; ceiling depends on genetic potential.
Should I run by pace or heart rate? +
Both have value. Pace is what races measure; heart rate is what your body experiences. Train by HR for easy long runs (Zone 2, 70-75% max HR), train by pace for intervals and tempo runs. Pace-based watch with HR monitor gives you both data sets simultaneously.
What pace should easy runs be? +
60-90 sec slower than 5K race pace. Easy runs are about volume and aerobic base, NOT speed. Most runners run their easy runs too fast and their hard runs too easy — a 90/10 split of true easy days to hard days is the secret of elite training.
How does altitude affect pace? +
~2% slower per 1,000 ft of elevation above 3,000 ft. A 25-min 5K at sea level becomes ~26-27 min in Denver (5,280 ft). Acclimatization helps but doesn't fully recover the difference. Many runners use altitude camps for training stimulus, then race at sea level.
Why is my treadmill pace different from outdoor? +
Treadmills don't perfectly simulate outdoor running — no wind resistance, consistent surface, the belt does some of the work. Many runners find 1% incline on the treadmill = closer to outdoor effort. Calibration also varies between treadmill brands.
What about negative splits? +
Negative split = second half of the race faster than first half. Considered optimal racing strategy because it conserves energy early. Average runners typically positive-split (first half faster); elites usually negative-split. Practice in training: turn around at the midpoint and run faster back.