Lean Bmi Calculator

Lean BMI & Body Mass Calculator

Determine your Lean Body Mass (LBM) and Body Mass Index (BMI) for a clearer picture of your health.

Male Female

Your Composition Analysis

Body Mass Index
0
Lean Body Mass
0 kg
Muscle, bone, water
Estimated Fat %
0%
Fat mass weight

Understanding Lean BMI and Body Composition

While the standard Body Mass Index (BMI) is a useful screening tool for the general population, it often fails to provide a complete picture for athletes, bodybuilders, or individuals with high muscle mass. This Lean BMI Calculator goes a step further by calculating your Lean Body Mass (LBM).

What is Lean Body Mass (LBM)?

Lean Body Mass represents the weight of everything in your body except for fat. This includes your muscles, bones, organs, connective tissue, and water content. Knowing your LBM is crucial for:

  • Calculating precise protein requirements for muscle maintenance.
  • Determining your Basal Metabolic Rate (BMR) more accurately.
  • Tracking true progress in the gym (fat loss vs. muscle gain).

The Boer Formula

This calculator utilizes the Boer Formula, which is widely recognized in clinical settings for estimating LBM based on height and weight. Unlike simpler calculations, the Boer formula accounts for the physiological differences between men and women.

BMI Range Category
Below 18.5 Underweight
18.5 – 24.9 Normal Weight
25.0 – 29.9 Overweight
30.0 and Above Obese

Example Calculation

Consider a male individual weighing 90 kg with a height of 185 cm:

  1. BMI: 90 / (1.85 * 1.85) = 26.3 (Overweight category).
  2. Lean Mass (Boer): (0.407 × 90) + (0.267 × 185) – 19.2 = 66.8 kg.
  3. Body Fat: 90kg – 66.8kg = 23.2kg (Approx. 25.7%).

By looking at both BMI and LBM, this individual can see that while their BMI is high, a significant portion of that weight is lean tissue.

function calculateLeanBMI() { var gender = document.getElementById("gender").value; var weight = parseFloat(document.getElementById("weight").value); var height = parseFloat(document.getElementById("height").value); if (!weight || !height || weight <= 0 || height <= 0) { alert("Please enter valid positive numbers for height and weight."); return; } // BMI Calculation var heightMeters = height / 100; var bmi = weight / (heightMeters * heightMeters); // LBM Calculation (Boer Formula) var lbm = 0; if (gender === "male") { lbm = (0.407 * weight) + (0.267 * height) – 19.2; } else { lbm = (0.348 * weight) + (0.096 * height) – 10.7; } // Body Fat Percentage Estimation var fatMass = weight – lbm; var fatPercentage = (fatMass / weight) * 100; // Determine BMI Category var category = ""; var catColor = "#27ae60"; if (bmi = 18.5 && bmi = 25 && bmi < 30) { category = "Overweight"; catColor = "#f39c12"; } else { category = "Obese"; catColor = "#e74c3c"; } // Display Results document.getElementById("bmi-val").innerHTML = bmi.toFixed(1); document.getElementById("bmi-cat").innerHTML = category; document.getElementById("bmi-cat").style.color = catColor; document.getElementById("lbm-val").innerHTML = lbm.toFixed(1) + " kg"; document.getElementById("fat-val").innerHTML = fatPercentage.toFixed(1) + "%"; document.getElementById("results-area").style.display = "block"; // Scroll to results on mobile if(window.innerWidth < 600) { document.getElementById("results-area").scrollIntoView({ behavior: 'smooth' }); } }

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