Fitness Calculators
Calorie Burn Calculator
Estimate calories burned across eighteen common activities using MET values combined with body weight and session duration for an accurate kcal figure.
Cycling FTP Calculator
Estimate cycling Functional Threshold Power from a 20-minute or ramp test, with a full seven-zone power training breakdown.
Exercise Calorie Estimator
Estimate calories burned using sex-specific heart-rate-based regression formulas from average heart rate, weight, age, and duration.
Half Marathon Pace Calculator
Calculate half marathon pace or finish time from the official 21.0975 km distance, with checkpoint splits at 5K, 10K, 15K, and 20K.
Heart Rate Zone Calculator
Calculate five training heart rate zones using the Karvonen method or percentage of max heart rate, from age and resting heart rate.
Hiking Time Calculator
Estimate total hiking time using Naismith's Rule, factoring trail distance, elevation gain, elevation loss, and walking pace.
Marathon Pace Calculator
Calculate marathon pace or finish time from the official 42.195 km distance, with checkpoint splits at 5K, 10K, half, and beyond.
One Rep Max Calculator
Estimate your one-rep max using the Epley, Brzycki, or Lombardi formula from a submaximal set, plus a full rep-range percentage chart.
Pace Calculator
Solve for pace, time, or distance from any two running variables, with results shown in hours, minutes, and seconds for any race distance.
Swim Calories Calculator
Estimate calories burned swimming using stroke-specific MET values across freestyle, backstroke, breaststroke, butterfly, and more.
VO2 Max Calculator
Estimate VO2 max using the Cooper 12-minute run test or a resting heart rate ratio method, with results mapped to a fitness category.
Training by Numbers Instead of Feel
Structured training relies on numbers that translate broad goals into specific, checkable targets — a heart rate zone to stay within during an easy run, a one rep max to base a lifting program's percentages on, a marathon pace that's actually sustainable for 26.2 miles rather than optimistic. Eleven calculators here cover running, lifting, and cardio training math.
Popular Fitness Calculators
Eleven tools span running, strength, and cardio metrics:
- One Rep Max Calculator — estimates a true one-rep max from a heavier set of reps, without needing to test it directly.
- Heart Rate Zone Calculator — finds training zones based on max or reserve heart rate for targeted intensity work.
- VO2 Max Calculator — estimates aerobic capacity from performance data like race times or heart rate response.
- Marathon Pace Calculator — finds a sustainable per-mile pace based on goal finish time.
- Calorie Burn Calculator — estimates energy expenditure for a given activity, duration, and body weight.
Why One Rep Max Calculators Use a Formula, Not a Test
Testing a true one-rep max directly carries real injury risk and requires fatigue-free conditions, so most one-rep max calculators instead use a formula (like Epley or Brzycki) that estimates it from a set taken to or near failure at a lighter weight — the accuracy holds up reasonably well in the 2-10 rep range but degrades noticeably for higher-rep sets, since the relationship between reps and percentage of max isn't perfectly linear across the full range. This is also why most strength programs base training percentages on a recently tested or estimated max rather than one from months earlier, since strength changes faster than many lifters expect.
Frequently Asked Questions
Why do heart rate zones use "max heart rate" when everyone's actual max differs?
Formula-based max heart rate (like 220 minus age) is a population average with meaningful individual variation, so heart rate zone calculators using a directly tested max heart rate are generally more accurate than age-based estimates.
Is VO2 max the best predictor of race performance?
It's a strong predictor of aerobic capacity, but running economy and the ability to sustain a percentage of VO2 max both matter too, which is why two runners with identical VO2 max scores can have different race times.
Explore More
Tracking nutrition alongside training? See the Nutrition Calculators, or check broader health metrics in the Health Calculators.