Calculate Outdoors A conditions almanac

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Editorial

About This Almanac

Calculate Outdoors exists to answer a question that activity calculators cannot: whether the conditions support going out at all, and what they will cost you.

What this site is

Most outdoor calculators are activity calculators. They take a distance and a pace and return a time. That is useful once you have already decided to go.

This site sits one layer above that. It takes the environment as its input — ultraviolet, daylight, temperature, humidity — and returns a decision. Four instruments, organised by condition rather than by activity, with reference material explaining the physiology and physics each one runs on.

Why the sections are conditions

Sun, daylight, heat and effort are the four variables that determine an outdoor day before the choice of activity does. A hiker, a cyclist, a runner and someone walking a dog face the same UV index and the same civil dusk. Organising around the environment rather than the sport removes duplication and makes the tools genuinely portable across activities.

How the calculators are built

Every instrument on this site is built on a published model, and each calculator page names the model it uses and states its limitations.

  • Sunrise, sunset and twilight use standard solar position equations with a zenith of 90.833 degrees for geometric sunrise and 96 degrees for civil twilight.
  • Apparent temperature uses the Rothfusz regression published by the National Weather Service, including its low- and high-humidity corrections.
  • Vitamin D synthesis is modelled on erythemal dose accumulation with Fitzpatrick-specific minimal erythemal doses and a photodegradation plateau.
  • Energy cost uses metabolic equivalents from the Compendium of Physical Activities.

None of these produce clinical-grade output, and each calculator page says so explicitly rather than burying it.

Who writes this

Calculate Outdoors is an independent publication produced in Pittsburgh, Pennsylvania. Articles are researched against primary literature and public standards documentation, with mechanisms explained rather than asserted. Where evidence is contested — and in several of these subjects it genuinely is — the article says so instead of picking a side for narrative convenience.

How this site is funded

Two sources, both disclosed. Display advertising through Google AdSense, and affiliate commission through the Amazon Services LLC Associates Program on the gear page. Neither influences editorial content, and no advertiser or affiliate partner reviews articles before publication.

Questions and corrections: contact page.