About Endurance Toolbox
Endurance Toolbox is a free collection of 42 calculators for runners, cyclists, swimmers, and triathletes. No signup, no paywall, and no hidden formulas.
Who builds it
The site is built and maintained by Gal Elmalah, an independent software developer. Every calculator, article, and correction is published under that name, so there is one accountable person behind the numbers.
How the calculators are made
- Each tool implements a published method (for example Daniels–Gilbert VDOT, Riegel, Coggan power levels, the 2025 USATF road age-grading tables) and cites it on the page.
- Formulas are covered by automated browser tests that check outputs against independently computed values, unit conversions, and edge cases.
- Every page states what the method cannot tell you. Estimates are labelled as estimates, not prescriptions.
How the site is funded
The calculators are free. The site is supported by display advertising and optionalreader donations. We do not sell sponsored placements, paid links, or rankings, and advertisers have no influence on content.
Corrections and contact
Found a wrong number, a broken source, or want a new tool? Use thefeedback form. Confirmed errors are fixed and the article's “Updated” date changes. See theeditorial policy for details.
Not medical advice
Calculators and articles provide general training information. Talk to a qualified professional before changing training, nutrition, or body weight, especially if you have a medical condition.