Free running calculators
Pace, prediction, heart rate, and fitness testing tools with the math done right, built by a running coach who uses them.
Pace and race
Plan goal paces, splits, and realistic predictions for race day.
Race pace calculator
Solve for pace, finish time, or distance for any race from the mile to 100 miles, with cumulative mile splits.
Plan your race pace →Race time predictor
Predict your time at every distance from one recent race result using the Riegel formula, with honest exponent options.
Predict your times →Splits calculator
Build even or negative-split pace bands per mile or kilometer, plus 400m lap splits for track races. Copy or print the table.
Build your pace band →Treadmill pace calculator
Convert treadmill mph to pace per mile and kilometer, and see the equivalent flat-ground pace for any incline.
Convert treadmill pace →Age grading calculator
Score any road race with the current WMA age-graded percentage, from the mile to 100 miles, using the 2025 factor tables.
Get your age grade →Training paces and heart rate
Keep easy days easy and hard days honest with the right ranges.
Zone 2 heart rate calculator
Find your aerobic base-building heart rate range using the MAF formula, percent of max HR, or the Karvonen method.
Find your Zone 2 range →Max heart rate calculator
Estimate max heart rate with the Tanaka formula, compare it with 220 minus age, and see why the old formula misses.
Estimate your max HR →MAF calculator
Get your MAF low heart rate training range with the full Maffetone health and training adjustment checklist.
Get your MAF range →Training pace calculator
Turn one race result into a fitness score, equivalent race times from 1500m to the marathon, and all five training paces with the published Daniels formulas.
Get your score and paces →Heart rate zone calculator
Build all five heart rate zones from percent of max, the Karvonen method, or your lactate threshold heart rate.
Build your five zones →Race day and environment
Adjust pacing for heat, altitude, and hills before they adjust it for you.
Heat pace calculator
Adjust your race pace for temperature and dew point with published hot-weather guidance, plus a band reference table.
Adjust for the heat →Altitude conversion calculator
Convert race times between altitude and sea level with the Daniels rule or the Bassett research model.
Convert for altitude →Grade-adjusted pace calculator
Turn any hill pace into its flat-ground equivalent with the Minetti energy-cost research behind GAP.
Get your GAP →Fueling and physiology
Fuel, fluids, form, and the body doing the work.
Carb intake calculator
Get grams-per-hour carb targets by duration and effort, with gel equivalents and honest guidance on gut training.
Get your carb targets →Sweat rate calculator
Turn the two weigh-in test into your personal sweat rate in liters and ounces per hour, with replacement guidance.
Measure your sweat rate →Running calorie calculator
Estimate net and gross calories burned from weight and distance, with an honest look at the error bars.
Estimate calories burned →Cadence and stride length
Relate pace, cadence, and step length, and get past the 180 steps per minute myth to what actually matters.
Check your cadence math →BMI calculator
The standard BMI formula with runner-specific context on what it can and cannot tell an athlete.
Calculate BMI →Tests and predictors
Measure fitness with field tests you can run without a lab.
VO2 max calculator
Estimate your VO2 max with five validated field tests: resting heart rate, Rockport walk, Queens College step test, Cooper run, and 2000m row.
Estimate your VO2 max →Cooper test calculator
Turn your 12-minute run distance into a VO2 max estimate with fitness classifications and standards tables.
Score your Cooper test →Yasso 800s calculator
Convert 800m repeat times to a marathon estimate and back, with an honest look at where the folk wisdom breaks.
Run the Yasso math →Couch to 5K calculator
The classic 9-week plan with a week-by-week progress checker, from the first 60-second jogs to a continuous 30 minutes.
Check your C25K progress →Ultra tools
Yard math, time on feet, and hour-by-hour fueling from the backyard to 100 miles. Built by an ultrarunner; you will not find these anywhere else.
Backyard ultra calculator
Yard pace, rest earned, and cumulative miles by the hour for last-one-standing racing, survival floor included.
Do the yard math →Time-on-feet estimator
Estimate ultra finish time from flat pace, distance, vert, and a fatigue factor, with the error bars stated honestly.
Estimate your day out →Ultra fueling planner
Hour-by-hour carbs, fluids, and sodium for a goal duration, with totals and a copyable crew-sheet plan.
Build your fueling plan →Hike-run blend pace
The napkin math of trail racing: average pace from the fraction you hike and the fraction you run.
Blend your pace →Built for the questions runners actually ask
Every tool here answers a real training question: what pace do I need, what can I race off my current fitness, how easy should easy days be, and how fit am I right now. The formulas come straight from the exercise science literature, the sources are named on each page, and every calculation is covered by automated tests so the math stays correct.
Start with the race pace calculator to turn a goal into a pace, check it against the race time predictor, and build a pace band for race day. For daily training, the Zone 2 calculator and MAF calculator keep your easy runs honest, and the VO2 max calculator tracks the engine over time.
Everything runs in your browser. Nothing you type is sent to a server, stored, or tracked.