Pace is the single number that ties every run together. It tells you how fast you are actually moving, whether you are on track for a goal race, and how a 25-minute 5K compares to a 3:30 marathon. This running pace calculator takes any distance and finish time and converts them into minutes per mile, minutes per kilometer, and miles per hour — then goes one step further and predicts what you could run at a different race distance using the classic Riegel formula.
Type in your distance, pick miles or kilometers, enter your hours, minutes, and seconds, and the result card updates instantly. Choose a target race distance and the calculator estimates your finish time there, so you can set realistic goals before you ever toe the starting line.
How to Use
- Enter the Distance you ran or plan to run. For a 5K, type
5; for a marathon, type26.22; for a half marathon, type13.1. - Set the Distance Unit to km for metric races (5K, 10K) or miles for imperial workouts. The calculator converts between them automatically using 1 mile = 1.609344 km.
- Enter your finish time in the three boxes: Hours, Minutes, and Seconds. If you ran a 25-minute 5K, put
0hours,25minutes, and0seconds. - Pick a Predict Time For race — 5K, 10K, Half Marathon, or Marathon. The engine applies the Riegel formula to estimate your finish time at that distance based on your current effort.
- Read the result card: Pace (min/mile) and Pace (min/km) show your normalized speed, Speed (mph) shows the equivalent road speed, and the predicted target time shows what you might run next.
The pace figure is the most useful number for training. If your easy runs are around 9:00 per mile and your race pace lands near 8:00 per mile, you have about a one-minute gap between easy and hard effort — a healthy spread that leaves room for recovery.
The Pace and Riegel Formulas
Your running pace is simply time divided by distance:
pace = total minutes ÷ distance
To get minutes per mile, divide your total minutes by the distance in miles. To get minutes per kilometer, divide by the distance in kilometers. Speed in miles per hour is the distance in miles divided by the time in hours.
The race prediction uses the Riegel formula, developed by runner and researcher Pete Riegel:
T2 = T1 × (D2 ÷ D1)^1.05
Where T1 is your known time over distance D1, and T2 is your predicted time over distance D2. The exponent 1.05 captures the fact that running twice the distance does not take twice the time — fatigue slows you down slightly, so the exponent sits just above 1. Think of it as a 5% penalty built in for the extra distance. This is why a 25-minute 5K predicts a marathon around 3:55 rather than a naive linear multiple.
Examples
Example 1 — A 5K in 25 minutes. Running 5 km (3.107 miles) in 25 minutes gives a pace of about 8:03 per mile, or 5:00 per kilometer, at roughly 7.5 mph. That is a solid beginner-to-intermediate road pace. If you choose "Marathon" as the target, the Riegel formula predicts a marathon of about 3 hours 55 minutes (234.7 minutes) — a realistic first marathon goal for someone who can hold this effort.
Example 2 — A 3:30 marathon. Finishing 26.219 miles in 3 hours 30 minutes (210 minutes) works out to about 8:01 per mile, or 4:59 per kilometer, at just under 7.5 mph. If you then ask the calculator to predict a half marathon, Riegel estimates around 1 hour 41 minutes — close to the common rule that your half marathon time is a little under half your marathon time.
Example 3 — Shaving 5% off your pace. If your current 10K pace is 9:00 per mile and you improve by 5%, you drop to about 8:33 per mile. Over a 6.2-mile race that improvement saves nearly three minutes — the difference between a near-miss and a personal best. Small percentage gains in pace compound quickly across longer distances.
FAQ
What is a good running pace for a beginner?
Beginner runners often start between 10:00 and 12:00 minutes per mile (about 6:15 to 7:30 per kilometer). A comfortable conversational pace is the right target at first; you should be able to speak in short sentences. As fitness builds, most runners drift toward 8:30–9:30 per mile for easy runs.
How do I convert minutes per kilometer to minutes per mile?
Multiply your minutes per kilometer by 1.609344. For example, a 5:00 per kilometer pace becomes 5.0 × 1.609344 = 8.05 minutes per mile, or about 8:03 per mile. The reverse conversion divides minutes per mile by 1.609344.
What pace is a 3-hour marathon?
A 3-hour (180-minute) marathon over 26.219 miles requires about 6:51 per mile, or 4:16 per kilometer, and holds an average speed near 8.7 mph. It is a standard club-runner benchmark and demands consistent, disciplined pacing from the first mile to the last.
How accurate is the Riegel race prediction?
Riegel's formula is a reasonable estimate for well-trained runners and distances between 5K and the marathon, usually within a few percent of actual performance. It is less accurate for very short sprints, ultra-distance events, or runners nearing their physiological limits. Use it to set goals, not to guarantee a finish time.
Should I run the same pace on easy days as on race day?
No. Easy days should be 30–90 seconds per mile slower than your race pace. Running every workout at race pace leads to fatigue, injury, and stalled progress. Reserve the faster pace for intervals, tempo runs, and races, and keep the bulk of your mileage comfortable.
How do pace bands help on race day?
Pace bands list the split time you should hit at each mile or kilometer to reach your goal. If your target is 8:00 per mile, you should pass mile 5 at 40:00, mile 13 at 1:44:00, and so on. Checking the band each mile keeps you from starting too fast — the most common mistake in distance running.
Disclaimer
This running pace calculator is provided for informational purposes only and is not medical advice. Pace and race predictions are estimates based on the inputs you enter and the standard Riegel formula; real performance varies with fitness, terrain, weather, elevation, sleep, and nutrition. Always warm up properly, listen to your body, and consult a qualified healthcare professional before beginning or changing a training program, especially if you have a pre-existing condition or are new to running.