About Calcpace

Our Mission

Calcpace started with a simple question — what would it take to build running calculators that are actually grounded in physiology, not just rough estimates? Most pace calculators online apply a single linear formula and call it done. We wanted something better.

We use the same models that coaches and sports scientists use — the Riegel formula for race prediction, the Daniels & Gilbert method for VO2max estimation, and the World Masters Athletics 2023 standards for performance by age. Every result comes with an explanation of the formula behind it, so you understand what the numbers mean.

What We Build

Calcpace provides free tools for runners of all levels:

• Pace Calculator — compute pace, time, or distance in km or miles
• Race Predictor — predict your finish time across distances using Riegel and Cameron formulas
• VO2max Estimator — estimate your aerobic capacity from any recent race result
• Performance by Age — compare your performance fairly across different ages and sexes
• Unit Converter — switch between km/mi, km/h/mph, and min/km/min/mi
• Race Calendar — upcoming marathons, half marathons, and major road races worldwide

Open Source at the Core

The math that powers Calcpace lives in an open-source Ruby gem also called calcpace, published on RubyGems. All the formulas are public, tested, and available for anyone to use or audit. We believe the science of running should be transparent.

Privacy First

The logged-in area of Calcpace is 100% ad-free and tracker-free. Public calculators display ads served by Google AdSense to cover infrastructure costs. We do not sell your data. We collect only what is necessary to make the service work.

Get in Touch

Built by runners, for runners. If you have a question, a bug report, or a suggestion, reach out at contact@calcpace.app.