Pace Calculator
Solve for pace, time or distance - with race time predictions
👟 Run details
Last updated June 2026
Method: Pace = time ÷ distance, computed in both minutes per mile and minutes per kilometer using the exact conversion 1 mile = 1.609344 km. Speed and predicted race times are derived from the same pace.
Included: Solving for pace, finish time or distance; min/mile and min/km pace; mph and km/h speed; and even-pace finish-time projections for 5K, 10K, half marathon and marathon.
Not included: Fatigue, terrain, elevation, heat, wind, walk breaks and individual physiology - all of which affect real performance. Results are estimates, not medical or training advice; consult a coach or physician before changing your training.
Running pace calculator: how it works
Say you run a half marathon (13.1 miles) in 2 hours flat. Divide the time by the distance: 120 minutes ÷ 13.1 miles = about 9:09 per mile, which is roughly 5:41 per kilometer and a speed of about 6.6 mph (10.5 km/h). That single pace then tells you what to expect at every other distance - and that is exactly what this pace calculator does: enter any two of pace, time and distance, and it solves for the third.
The pace formula
Pace, time and distance are linked by one simple relationship. Pace is just time divided by distance:
pace = time ÷ distance • time = pace × distance • distance = time ÷ pace Because the three are tied together, knowing any two gives you the third. The calculator keeps the time in seconds internally, so it can switch cleanly between minutes per mile and minutes per kilometer (1 mile = 1.609344 km) without rounding drift.
Reading pace vs. speed
Runners usually think in pace (how long it takes to cover one mile or kilometer), while treadmills and cyclists think in speed (mph or km/h). They are inverses of each other: a faster runner has a lower pace number but a higher speed number. An 8:00 per-mile pace equals 7.5 mph; a 10:00 per-mile pace equals 6.0 mph. The calculator shows both so you can match a treadmill setting to your outdoor pace.
Race time predictions and even pacing
Once it knows your pace, the calculator projects finish times for the four standard road distances - 5K, 10K, half marathon (21.0975 km) and marathon (42.195 km) - by assuming you hold that exact pace the whole way. This even-pace model is the cleanest way to set a goal, but it is optimistic for longer races: as distance grows, most runners slow slightly, so a marathon predicted purely from 5K pace will usually come in faster than reality. Use the projections to set realistic splits, then adjust based on your own training history.
Using pace to plan a goal time
- Have a goal time? Set the mode to "Pace", enter the race distance and your target time, and read off the per-mile and per-km pace you need to hold.
- Know your pace? Set the mode to "Finish time" to see how long a given distance will take at that pace.
- Have a time budget? Set the mode to "Distance" to see how far you can go in a fixed amount of time at a chosen pace.
- Match a treadmill: use the mph / km/h speed figure to dial in the machine.
How to use this calculator
You only need two of the three values - pace, time, or distance - and the tool fills in the rest. Work through it in order:
- Pick what to solve for: choose "Pace", "Finish time", or "Distance" so the calculator knows which field to leave blank.
- Choose your unit: miles or kilometers. The result is shown in both min/mile and min/km regardless, but the distance you type uses the unit you select.
- Enter the distance: type a custom number (for example 3.1 miles) or pick a standard race - 5K, 10K, half marathon, or marathon.
- Enter time or pace: use the hours, minutes, and seconds fields. For pace, enter the minutes and seconds it takes to cover one mile or one kilometer.
- Read the result: the calculator returns the missing value plus your speed in mph and km/h, and projects finish times for the four standard distances.
Everything updates instantly as you type, so you can nudge a number up or down and watch how your goal pace or finish time shifts.
A second worked example: hitting a sub-25 5K
Suppose you want to break 25 minutes for a 5K (3.107 miles). Set the mode to "Pace", choose the 5K distance, and enter a target time of 25:00. The calculator divides 25 minutes by 5 km to return about 5:00 per kilometer, which is roughly 8:03 per mile and a speed of about 7.5 mph (12 km/h). That tells you the steady effort to rehearse in training. Flip the mode to "Finish time", keep the 8:03 per-mile pace, and switch the distance to 10K and the projection jumps to about 50:00 - a quick way to see what your 5K fitness implies for the next distance up.
Key running terms explained
- Pace: how long it takes to cover one unit of distance, written as minutes:seconds per mile or per kilometer. A lower number is faster.
- Speed: how much distance you cover per hour (mph or km/h). It is the inverse of pace - a higher number is faster.
- Split: the time recorded for a segment of a race, such as each mile or each 5K. Comparing splits shows whether you sped up or slowed down.
- Negative split: running the second half of a race faster than the first. Many coaches consider it the most reliable way to race well.
- Even pacing: holding a single, steady pace from start to finish - the assumption behind every projection on this page.
- Marathon (26.2 miles / 42.195 km) and half marathon (13.1 miles / 21.0975 km): the two most common long-road distances, alongside the 5K (3.107 miles) and 10K (6.214 miles).
What changes your real pace
The math here assumes a flat course on a calm day, but several factors push your actual pace away from the number on screen:
- Distance and fatigue: almost everyone slows as a race gets longer, which is why a marathon predicted from 5K pace is optimistic.
- Elevation and terrain: hills, trails, sand, and uneven ground all cost time compared with a flat, paved course.
- Heat and humidity: warm, humid conditions raise your heart rate and can add 10-30 seconds per mile or more.
- Wind: a headwind slows you noticeably, and a tailwind rarely gives all of it back.
- Walk breaks and stops: water stations, traffic lights, and run-walk strategies lower your average pace even if your running pace stays steady.
- Fitness and rest: training, sleep, fueling, and how fresh your legs are on the day all move the number.
Who this calculator is for
- Goal-race runners working out the exact pace to hold for a target finish time.
- New runners who want to translate a treadmill speed into an outdoor pace, or vice versa.
- Walkers and joggers tracking progress, since pace works the same way at any speed.
- Coaches and pacers setting split targets for a training group.
- Anyone curious how their 5K time stacks up against a 10K, half, or full marathon at the same effort.
Tips to improve your pace
Pace is an output of fitness, so improving the number usually means training smarter rather than just trying harder on race day. Common approaches include:
- Build an easy-run base: most weekly mileage at a conversational pace develops aerobic endurance with low injury risk.
- Add a little faster work: intervals or tempo runs once or twice a week can raise your sustainable pace over time.
- Practice goal pace: rehearse the exact pace this calculator gives you so it feels familiar on race day.
- Pace the start conservatively: starting a few seconds slower than goal pace often produces a faster finish.
- Recover properly: sleep, fueling, and rest days let training adaptations stick. Pace targets are a planning tool, not training advice - consult a coach or physician before making big changes.
Limitations and assumptions
This is a planning estimate, not a performance prediction tailored to you. Keep these assumptions in mind:
- It assumes a single even pace across the whole distance and a flat course in neutral conditions.
- Race-time projections hold your pace constant as distance grows, so longer-distance estimates are an optimistic best case.
- It does not model fatigue, elevation, heat, wind, or walk breaks, all of which affect real finish times.
- It uses the exact conversion 1 mile = 1.609344 km; rounding in the displayed minutes and seconds can differ by a second or two from a stopwatch.
Sources
- National Institute of Standards and Technology (NIST) - unit conversion (1 mile = 1.609344 km).
- Centers for Disease Control and Prevention (CDC) - Physical Activity Basics.
- U.S. Department of Health & Human Services - Physical Activity Guidelines for Americans.
⚠️ Common mistakes & edge cases
Mixing up miles and kilometers
A 6:00 pace per mile is a very different effort from 6:00 per kilometer (about 9:39 per mile). Always check which unit you selected - the calculator labels both, but the gap is large.
Confusing pace with speed
Pace and speed move in opposite directions. A bigger speed number is faster, but a bigger pace number is slower. Don't assume "9" beats "8" - 8:00 per mile is faster than 9:00 per mile.
Trusting the marathon prediction literally
Projecting a marathon straight from your 5K pace assumes you never slow down over 26.2 miles. Almost everyone fades somewhat, so treat the longer-distance estimates as an even-pace best case, not a guarantee.
Entering seconds over 59
Time and pace use minutes and seconds, so seconds should stay between 0 and 59. Typing "1:75" instead of "2:15" will throw the math off - roll extra seconds into the next minute.
❓ Frequently asked questions
How do I calculate my running pace?
Pace is your time divided by your distance. For example, running 5 miles in 45 minutes is 45 / 5 = 9 minutes per mile. To get pace per kilometer, divide total seconds by total kilometers. This calculator does the math both ways and also shows your speed in mph and km/h.
What is a good running pace?
It depends entirely on your fitness, age, distance and goal. Many recreational runners cover a mile in roughly 9 to 12 minutes (about 5.6 to 7.5 km/h), while a casual jog might be 12 to 15 minutes per mile. The best target is a pace you can sustain while still being able to talk; there is no single 'good' number.
How do you convert min/mile to min/km?
Multiply your pace per mile by 0.621371 to get pace per kilometer, because one kilometer is 0.621371 of a mile. For example, a 9:39 per-mile pace is about 6:00 per kilometer. The calculator shows both at once so you don't have to convert by hand.
Can this predict my marathon time?
It projects your finish time at 5K, 10K, half marathon and marathon by holding the pace you enter constant across the full distance. This is a simple even-pace estimate; real race times over longer distances are usually a bit slower because pace drifts as fatigue builds, so treat the marathon figure as an optimistic best case.
What is marathon pace?
Marathon pace is the steady speed you plan to hold for all 26.2 miles (42.195 km). For a 4-hour marathon that is about 9:09 per mile (5:41 per km). Enter your goal time and the marathon distance, set the calculator to 'Pace', and it returns the exact pace you need to hold.
Should I run at the same pace the whole race?
Even or slightly negative splits (running the second half as fast or faster than the first) are a common strategy because starting too fast often leads to slowing badly later. This calculator assumes a single even pace; many runners deliberately bank a few seconds of margin rather than running dead-even.
Is faster pace always better training?
No. Most endurance plans mix easy runs at a conversational pace with a smaller amount of faster work. Running every session hard raises injury and burnout risk. Pace targets are a planning tool, not training advice - consult a coach or physician before making big changes.
How do I convert pace to speed in mph or km/h?
Speed is distance divided by time, the inverse of pace. To get mph, divide 60 by your pace in minutes per mile; an 8:00 (8.0) per-mile pace is 60 / 8 = 7.5 mph. For km/h, divide 60 by your pace in minutes per kilometer. This calculator shows both speeds automatically, which is handy for matching a treadmill setting to an outdoor pace.
What pace do I need to run a sub-2-hour half marathon?
A 2-hour half marathon (13.1 miles / 21.0975 km) works out to about 9:09 per mile, which is roughly 5:41 per kilometer. To break two hours you need to hold slightly faster than that the whole way. Set the calculator to 'Pace', choose the half marathon distance, and enter your goal time to see the exact pace for any target.
Why is my real race time slower than the prediction?
The projections assume you hold one even pace on a flat course in neutral conditions. In reality, fatigue builds over distance and hills, heat, humidity, wind, and walk breaks all add time. That is why estimates for longer distances - especially the marathon - usually come in faster than what most runners actually achieve. Treat them as an optimistic best case.
💡 Good to know
Pace and speed are inverses
A lower pace number means you are running faster, but a higher speed number means the same thing. If you are unsure, glance at both: 8:00 per mile and 7.5 mph describe the exact same effort.
Longer-distance predictions run optimistic
The marathon and half-marathon projections assume you never slow down. Most runners fade as distance grows, so add a buffer when you set a goal time from a shorter race result.
Rehearse your goal pace
Once the calculator gives you a target pace, practice it in training so it feels natural on race day. Starting a few seconds slower than goal pace often leads to a faster finish.