Methodology and sources

Planning numbers, not black-box outputs

Running Toolkit calculators are built for planning and comparison. Some outputs are exact arithmetic, while physiology outputs are estimates from common field formulas.

Last updated · June 9, 2026

Exact arithmetic

Pace, speed, distance conversion, and split calculations are deterministic once time and distance are known.

Estimate-based outputs

Calories, race predictions, VO2 max, and heart-rate zones use field formulas and should be read as planning ranges.

Stated limits

Every estimate is affected by route accuracy, weather, terrain, fatigue, device quality, and individual variation.

How the calculators work

Every result has a method and a limit

Pace and speed

Pace, speed, distance conversion, and split calculations use deterministic arithmetic. They are only as accurate as the distance and time values entered.

Calories

Running calories use 2024 Compendium of Physical Activities running MET values, body weight in kilograms, duration in hours, and a heuristic elevation adjustment.

Race predictions

Race predictions use Riegel-style endurance profiles with visible exponents, then need adjustment for course profile, weather, and training evidence.

Heart rate and VO2 max

VO2 max uses the Cooper 12-minute run field-test estimate. Heart-rate zones use either a known max heart rate or the Tanaka-style estimate 208 - 0.7 x age.

Review policy

Author, publisher, and correction process

The goal is to make the calculator logic easy to inspect: what formula is used, what source supports it, and where the result should not be overread.

Author

Mark Portman is an amateur runner and the creator of Running Toolkit. He geeks out on running data and builds calculators that make pace, speed, and training estimates easier to understand.

Publisher

Running Toolkit is published by Hiddenwork Development. No external reviewer is currently listed for the guides or calculators.

Corrections

Running Toolkit pages are reviewed when formulas, sources, implementation tests, or calculator behavior change. Corrections prioritize transparent formulas, source links, and plain-language limitations.

Limitations

These calculators do not replace lab testing, medical advice, a coach, or a sports dietitian. Real-world results vary with running economy, route measurement, surface, wind, heat, altitude, fatigue, fueling, and device accuracy.

Primary references

Source links behind the estimates

2024 Compendium of Physical Activities Riegel-style race prediction formula reference Cooper 12-minute field test Max heart rate formula context

Related guides

See the methodology in context

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