About Caterpillar.fit

Small inputs, steady crawls, complete metamorphosis.

The site is named for the caterpillar because that is what body transformation actually looks like: not a sudden emergence of wings, but weeks of unglamorous, consistent work that eventually compounds into something unrecognisable. Our job is to give you the numbers that make that work deliberate — how much to eat, how hard to lift, how fast to run.

Every formula is published and citable

• TDEE & BMR — Mifflin-St Jeor (1990); Katch-McArdle when you supply body fat
• Body fat — US Navy circumference method, Hodgdon & Beckett (1984); categories per the American Council on Exercise
• One-rep max — Epley, Brzycki, Lombardi, O'Conner and Mayhew equations, shown side by side
• Ideal weight — Devine (1974), Robinson (1983), Miller (1983) and Hamwi (1964)
• Macros, protein, water — sports-nutrition consensus ranges converted to your numbers

Where the science is fuzzy, we say so on the page — every calculator includes its limits and the honest error bars.

The privacy promise

Every calculator runs entirely in your browser. Nothing you type is transmitted, stored or logged — there is no account, no cookie banner, because there is nothing to banner about. See the privacy policy for the plain-English version.

A word on health decisions

Caterpillar.fit is informational, not medical advice. If you are managing a condition, pregnant, under 18, or planning big changes to diet or training, run the numbers here and then past a qualified professional.