Fitness Calculators

Fitness calculators give endurance athletes, lifters, and general-population exercisers the standard math their training relies on: target heart rate zones, VO2 max estimates, one-rep-max projections, calorie burn estimates, and pace/distance/time conversions. We've prioritized the formulas with the strongest published evidence and broadest acceptance in coaching literature.

The target heart rate zone calculator uses the Karvonen formula (heart rate reserve method) for personalized zone-1 through zone-5 thresholds, with the Tanaka formula (208 - 0.7 × age) as the max heart rate estimator. This is more accurate than the older 220-minus-age rule for most adults, especially older athletes. The VO2 max calculator uses the Cooper test and Rockport walking test protocols, both validated in submaximal-fitness-assessment literature.

For strength training, the one-rep-max calculator implements the most common projection formulas (Epley, Brzycki, Lombardi) and shows results from each so you can compare. The right answer depends on the rep range — Epley tends to over-project at very low reps, Brzycki at very high reps.

Calorie-burn calculators use MET (metabolic equivalent of task) values from the 2024 Compendium of Physical Activities (Ainsworth et al.). The walking calories and cycling power calculators are the most-used specialty tools. Cycling power uses the standard Coggan-derived FTP and power-zone framework that virtually all training-with-power coaches use.

Pace and distance conversions are exact (math, not estimates) for running, swimming, and cycling, including conversions between min/mile and min/km that confuse many recreational runners traveling internationally.

Formulas use peer-reviewed sources (ACSM Guidelines for Exercise Testing and Prescription, current edition; Compendium of Physical Activities; Tanaka et al. JACC 2001 for max heart rate). These are estimates intended for healthy adults exercising for general fitness or recreational competition. Athletes with cardiovascular conditions, medications affecting heart rate, or other medical considerations should consult a sports cardiologist or their physician before relying on heart-rate-based training prescriptions.