RunCalc
Pace, race predictions, VO2max, heart rate zones, and treadmill conversions. Train smarter with data.
Pace Calculator
Calculate pace, speed, time, or distance. Enter any two to find the rest.
Race Time Predictor
Predict race times from a recent result using the Riegel formula.
VO2max Estimator
Estimate your VO2max from a recent race time using the Daniels formula.
Heart Rate Zone Calculator
Calculate training zones from max heart rate or resting + max (Karvonen method).
Treadmill Pace Converter
Convert treadmill speed (mph) to pace per mile/km. Calculate incline equivalents.
About RunCalc
RunCalc provides free running calculators for recreational joggers, marathon trainees, and competitive athletes. Calculate pace, predict race times, estimate VO2max, and find your training zones.
All tools run in your browser. Share calculations via URL — perfect for texting your training partner or bookmarking for race day.
Pace calculation: pace is the time to run one unit of distance. Pace (min/mile) = total time in minutes ÷ distance in miles. A runner finishing a 10K (6.214 miles) in 50 minutes runs 50/6.214 = 8:03 per mile. Speed and pace are reciprocals: if pace is 8 min/mile, speed is 60/8 = 7.5 mph. Converting: mph = 60 / pace_in_minutes.
VO₂ max estimation from race performance: Jack Daniels' formula estimates VO₂ max from a best-effort race time. The percentage of VO₂ max a runner can sustain decreases as duration increases. A 1-mile effort uses roughly 95–100% of VO₂ max; a marathon uses approximately 75–80%. Race calculators use these percentages (velocity at VO₂ max = vVO₂max) to estimate fitness and predict equivalent times at other distances.
Calorie burn estimation: running energy expenditure is approximately 0.63 × body weight in lbs per mile for most runners (roughly 100 calories per mile for a 158 lb runner). This is nearly independent of speed over typical recreational running ranges — running faster burns the same calories per mile, just in less time. Wind, hills, and surface add additional cost: uphill at 10% grade roughly doubles energy expenditure per mile; treadmill with 1% incline closely approximates outdoor flat running energy cost.
Heart rate training zones: using maximum heart rate (HRmax ≈ 220 − age as a rough estimate), Zone 2 (aerobic base) is 60–70% HRmax; Zone 3 (tempo) is 70–80%; Zone 4 (threshold) is 80–90%; Zone 5 (VO₂ max intervals) is 90–100%. Most training volume for endurance runners (70–80% of weekly miles) should be in Zone 2 — conversational pace — with only 20–30% of miles in higher zones.