About Running Calculators

Running Calculators is a free, science-based set of tools designed to help runners of all levels train smarter and reach their goals. It is built and maintained by a running coach with a decade of ultramarathon experience, the coach behind Coach Carl. The mission is simple: make exercise science accessible to every runner.

Whether you are planning your first 5K or chasing a Boston Marathon qualifier, these calculators provide instant, accurate insights into your race pace, heart rate zones, and aerobic fitness. All calculations run directly in your browser. No data is sent to servers, and we do not collect any personal information.

The pace calculator helps you plan race strategies and training runs. The Zone 2 heart rate calculator uses proven methods from exercise physiology, including the Maffetone formula and the Karvonen method. The VO2 max estimator offers five validated field tests that do not require expensive lab equipment.

Every formula on this site comes from the published exercise science literature, and each calculator page documents how its numbers are produced so you can check the math yourself.