Lean Mass Calculator
About the project

The Reality Check You Need. Not Just Another Number.

We've all been there: staring at a number on a screen, panicking, and wondering what it actually means. Most health calculators just spit out a meaningless digit with zero context. We built Lean Mass Calculator because you deserve cold, hard facts about your body composition—backed by actual clinical science—so you can stop guessing and start taking action.

3Published formulas
100%Browser-only, no data sent
FreeAlways, no account needed

Parent company & legal entity

Lean Mass Calculator is operated by HealthTools Media Ltd., an independent digital publisher focused on transparent, evidence-based health and fitness calculation tools. The site is an educational resource and its calculators are screening tools — they do not replace advice from a qualified healthcare professional. For full legal detail see our Terms of Use and Privacy Policy.

HealthTools Media Ltd., 27 Old Gloucester Street, London WC1N 3AX, United Kingdom
Our team

Who We Are

We are a tight-knit crew of clinicians, dietitians, and engineers who know exactly what it feels like to panic when a health metric doesn't make sense. We believe a number is totally useless unless you understand the math behind it—and how to fix it.

Editorial Team

Health and Fitness Content Reviewers

Our editorial team reviews each health calculator against the original published equations and clinical reference data. We focus on making the math transparent and the results easy to interpret. Calculations are estimates and are not a substitute for professional medical or dietary advice.

  • Formulas sourced from peer-reviewed publications: Boer (1984), James (1976), Hume (1966)
  • Reviewed against published clinical body-composition reference ranges

Engineering Team

Product & Accessibility

Builds the calculation engine and keeps the site fast, accessible, and privacy-first across every device. WCAG AA compliant from day one.

  • Web Performance
  • WCAG AA
  • Privacy-First Architecture

Scientific Review Board

Formula Validation & Citation

Validates every formula against original peer-reviewed publications and ensures reference ranges are drawn from recognised clinical bodies such as WHO, CDC, and ACE.

  • PubMed Research
  • Clinical Reference Data
  • ACE Guidelines
Our story

Our Story

Lean Mass Calculator started out of pure frustration. You know the drill: you google a calculator, it spits out a number with zero explanation, and the page is buried in terrible ads. One of our clinicians wanted a clean lean mass estimate for a patient consultation and couldn't find a single tool that actually cited its formula.

So we built the solution. What started as one blunt, honest calculator grew into an entire library. We built Lean Mass Calculator for the people who want to understand the numbers, verify the math themselves, and stop guessing. No ads, no tracking, just the hard facts.

Our mission

What We Do

We take dense, peer-reviewed medical formulas and turn them into something you can actually use in seconds. Then, we cut through the noise and tell you exactly what the result means for your training or diet.

Every calculator on this site shows its working, cites the original research, and tells you the reality. We build the tools that answer the only question that actually matters: “Okay, so what do I actually do with this number?”

We cover lean body mass, body fat percentage, FFMI, protein targets, BMR, and TDEE. They are all free, blazingly fast, and completely private.

Trusted source statement

Why You Can Trust Us

We earn trust the boring way: by showing our assumptions, citing recognised standards, and being honest about what a screening number can and can't tell you.

You can read the methodology behind every category on the relevant guide page, and cross-check the math yourself — our formulas are fully visible and documented.

Documented formulas

Each calculator explains the exact equation it uses and how edge values are handled.

Recognised standards

Health categories map to published WHO / CDC guidance, not figures we invented.

Clear scope boundaries

We screen, we don't diagnose. Every result page points you to a clinician for decisions.

Peer-reviewed sources

Every formula is traceable to the original academic paper, cited and linked on each tool page.

Social proof

What People Are Saying

Trusted by fitness professionals, dietitians, and thousands of individuals tracking body composition goals.

★★★★★

Finally a lean mass calculator that actually shows its working. I cross-checked the Boer formula manually and it matched perfectly. Bookmarked.

James R.Personal Trainer, London
★★★★★

I use this with my sports nutrition clients. The protein target output saves me time and the citations make it credible for professional use.

Dr. Sarah K.Registered Dietitian
★★★★★

No ads cluttering the page, no sign-up, no data sent anywhere. Just the calculation. Exactly what I was looking for.

Marcus T.Competitive Powerlifter
★★★★★

The comparison between Boer, James, and Hume formulas is really helpful. You can see why formula choice matters for certain body types.

Priya M.Exercise Physiologist
Core principles

What Makes This Different

Exact Math, Not Guesses

Every result comes straight from the published formula — Boer (1984), James (1976), Hume (1966) — with no rounding shortcuts or averages standing in for the real calculation.

Sourced & Cited

Categories and thresholds follow recognised standards from bodies like the WHO, CDC, and ACE, with sources listed on every relevant page.

No Account Required

The calculator runs entirely in your browser. Nothing you enter is sent to a server, stored, or used to identify you — ever.

Server-Rendered for Speed

Content and FAQs ship as crawlable static HTML. The interactive calculator hydrates on top without replacing the page — fast on any connection.

Plain About Limits

We document where a metric falls short — athletes, children, and edge cases — instead of pretending one number fits every body.

Open & Auditable

The formula, the categories, the assumptions — all visible. Check the numbers against your own and verify every step yourself.

Roadmap

What's Coming Next

Tap a milestone to see what it includes.

Contact & legal

Get in Touch

Registered Office

HealthTools Media Ltd.
27 Old Gloucester Street
London WC1N 3AX
United Kingdom

Email

hello@leanmasscalculator.com

For corrections, feedback, or press enquiries