Pace Calculator
Solve for running pace, finish time or distance from whichever two you know, and see predicted finish times for a 5K, 10K, half marathon and marathon at that pace.
How to use this calculator
- Choose what you want to solve for: pace (if you know the distance and time you ran), time (to predict a finish time from a target pace), or distance (to see how far a given pace and time would cover).
- Fill in the two known values — the calculator hides whichever field you asked it to solve for.
- Read the result, then check the table for what that pace would predict over standard race distances.
How the calculation works
Pace = total time ÷ distance; Time = pace × distance; Distance = total time ÷ pace; Speed = distance ÷ total time- total time
- Hours, minutes and seconds combined into a single time
- distance
- The distance covered, in miles or kilometres
- pace
- Time per mile or per kilometre
Pace and speed are reciprocals of each other — pace is time per unit distance, speed is distance per unit time — so both are shown from the same two numbers.
Whichever two of pace, time and distance you supply, the third is solved directly from the other two — the underlying relationship (distance = speed × time) is the same in every direction, just rearranged.
Race predictions simply scale your pace per kilometre up to each standard race distance; they say nothing about whether that pace is sustainable for longer.
Worked example
5 miles in 42:00 — solve for pace
- Pace per mile: 42:00 ÷ 5 = 8:24 per mile.
- 5 miles = 8.0467 km, so pace per km: 42:00 ÷ 8.0467 = 5:13 per km.
- Speed: 5 miles ÷ 0.7 hours = 7.14 mph.
- At that per-km pace, a marathon (42.195 km) predicts 3:40:14.
Result: 8:24/mile (5:13/km), 7.14 mph — marathon prediction 3:40:14
10 miles at an 8:00/mile pace — solve for time
- Total time = pace × distance = 8:00 × 10 = 80:00.
- 80 minutes is 1 hour 20 minutes.
Result: Predicted time 1:20:00
1 hour at a 9:00/mile pace — solve for distance
- Distance = total time ÷ pace = 60:00 ÷ 9:00 = 6.67 miles.
- 6.67 miles converts to 10.73 km.
Result: Distance covered 6.67 miles (10.73 km)
"Ran 40 miles in 2 hours — how many miles in one hour?" (a rate word problem)
- Miles per hour is just distance ÷ time: 40 ÷ 2 = 20 miles in one hour.
- The same rate as a pace: 120 minutes ÷ 40 miles = 3:00 per mile.
- This is the unitary method every rate problem uses — find the amount for ONE unit (one hour), then scale to any number of hours.
Result: 20 miles in one hour (20 mph, or 3:00 per mile)
"Runs 4 miles in 20 minutes — how far in 45 minutes at this rate?"
- First find the rate for one unit: 20 minutes ÷ 4 miles = 5:00 per mile.
- Then apply it to the new time: 45 minutes ÷ 5:00 per mile = 9 miles.
- Check by scaling instead: 45 ÷ 20 = 2.25, and 4 miles × 2.25 = 9 miles — same answer, either route.
Result: 9 miles in 45 minutes
Pace versus speed
Pace and speed describe the same underlying rate of motion from two different angles: speed is distance covered per unit of time (miles per hour), while pace is time spent per unit of distance (minutes per mile). Runners overwhelmingly talk in pace rather than speed, mostly because race distances are fixed and known in advance — for a 5K or a marathon, the practically useful question is how long each mile or kilometre takes, not how many miles would be covered in an hour of running at that effort.
Training paces and what they are generally used for
Runners and coaches commonly describe training in terms of named effort levels rather than a single pace, since different training goals call for different intensities:
- Easy or recovery pace — a comfortable, conversational effort used for the majority of training volume in most structured plans, to build aerobic fitness without excessive fatigue.
- Tempo pace — a "comfortably hard" sustained effort, typically used to build the ability to hold a faster pace for longer.
- Interval or speed pace — short, faster repetitions with recovery between them, aimed at raising top-end speed and running economy.
- Race pace — the specific pace targeted for an upcoming event, often practiced directly in some training sessions as the race approaches.
Why a flat pace overpredicts longer distances
Simply scaling a known pace up to a longer distance — as the finish-time table above does — assumes the same effort holds for the whole race, which becomes progressively less realistic the further the target distance is from what was actually run. Endurance and fuel availability decline over distance in a way that a straight-line projection does not capture, which is why more sophisticated race-time prediction formulas apply a fatigue factor that grows with distance, rather than treating pace as constant regardless of how far it is being projected.
Where common race distances come from
The 5K and 10K are metric distances that map neatly onto the metric system used for track and road racing worldwide. The marathon’s distance, 26.2 miles (42.195 km), is less tidy — it was standardized based on the course used at the 1908 London Olympics, and was later fixed as the official distance by the sport’s governing body. The half marathon is, as the name suggests, defined as exactly half that distance.
What this assumes, and where it stops
Assumptions
- Pace is treated as perfectly even for the whole distance entered — no allowance for a faster or slower start, hills, or fatigue.
Limitations
- Race predictions assume the same even pace holds over a very different distance, which is optimistic for anything much longer than what you actually ran — an accurate 5K time typically overpredicts marathon speed by a wide margin.
- Does not account for elevation gain, terrain, heat, or altitude, all of which change what pace is realistic on race day.
Common questions
Why is my predicted marathon time probably too fast?
Endurance drops off over distance faster than a straight-line scale-up suggests — the physiology of sustaining a 5K pace and a marathon pace are different. Race-prediction formulas (like Riegel's) apply a fatigue exponent for exactly this reason; this calculator instead shows a simple even-pace projection, which is a ceiling, not a realistic target, for distances well beyond what you ran.
What is a good pace for a beginner?
There isn't a universal number — it depends entirely on your current fitness. A more useful beginner goal is a pace you can hold in conversation (roughly 60–70% of max heart rate), then let races and Target Heart Rate Calculator sessions tell you what number that actually is for you.
Why show both miles and kilometres?
Races and watches use both depending on the country and the event, and pace "feels" different in each — 5:00/km sounds fast to someone used to thinking in minutes per mile, even though it is the same speed. Showing both avoids the conversion error of comparing the wrong units.
Can I use this to plan a target finish time instead of analysing a run I already did?
Yes — switch "Solve for" to Time, enter the race distance and the pace you want to hold, and the calculator gives the finish time that pace would produce. Switch it to Distance if instead you know how long you can run and at what pace, and want to see how far that takes you.
How do I solve word problems like "ran 40 miles in 2 hours, how far in one hour"?
These are rate problems, and the method is always the same two steps: find the amount for ONE unit, then scale. 40 miles in 2 hours is 40 ÷ 2 = 20 miles per one hour. If the question then asks about 3 hours, multiply: 20 × 3 = 60 miles. This calculator does the same arithmetic — enter the distance and time you know, solve for pace, and the per-hour speed is shown alongside; switch to solving for distance to apply that rate to any other time.
How do I work out my time per mile?
Divide total time by total distance. A 42-minute run over 5 miles is 42 ÷ 5 = 8.4 minutes per mile, and 0.4 of a minute is 24 seconds — so 8:24 per mile. The calculator does the minute-to-second conversion for you, which is where hand arithmetic usually slips.
Distance, pace, time — which two do I need?
Any two give you the third, because they are one relationship rearranged: pace = time ÷ distance, time = pace × distance, distance = time ÷ pace. Pick the one you want as the answer under "Solve for" and the calculator asks for the other two.
Formula and content last reviewed on .
Built and maintained by Dev Mokshrajsinh.
Results are estimates for information only, not professional advice.
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