FFMI (Fat-Free Mass Index), Normalized FFMI & Casey Butt Muscular Potential Calculator

Compute Lean Body Mass, FFMI (kg/m²), and 1.80m-normalized FFMI from weight, height, and body fat %.

Normalized Fat-Free Mass Index (FFMI)
23.05 kg/m²
Fat-Free Lean Body Mass (LBM) 72.66 kg
Unadjusted FFMI (LBM ÷ Height²) 22.93 kg/m²
Total Adipose Fat Mass 11.34 kg
Inputs
⚡ Scenarios:
kg
Total body weight in kilograms.
cm
Standing height in centimeters.
%
Estimated body fat percentage (%).
Results & Graph
Normalized Fat-Free Mass Index (FFMI)
23.05 kg/m²
Fat-Free Lean Body Mass (LBM)
72.66 kg
Unadjusted FFMI (LBM ÷ Height²)
22.93 kg/m²
Total Adipose Fat Mass
11.34 kg

Normalized Fat-Free Mass Index (FFMI)

Graph 1 • FFMI & Natural Muscle Limit • Domain Architecture & Live Telemetry Maps Total Body Weight Kg, Standing Height Cm, Body Fat Percentage through FFMI & Natural Muscle Limit Formula.
FFMI & Natural Muscle Limit • Clinical & Physiological Reference Scale Low / Baseline Target / Reference Elevated / Watch High / Action Normalized Fat-Free Mass Index (FFMI): 23.05 kg/m² Fat-Free Lean Body Mass (L 72.66 kg Unadjusted FFMI (LBM ÷ Hei 22.93 kg/m² Total Adipose Fat Mass 11.34 kg
Graph 2 • Normalized Fat-Free Mass Index (FFMI) Across Total Body Weight Kg Sweep (40% → 160%) Evaluates LBM_kg = Weight_kg × (1 − BodyFat%/100); FFMI = LBM_kg / Height_m²; across 7 operating points (current input highlighted).
0 kg/m² 20.25 kg/m² 40.49 kg/m² 9.30 33.60kg 13.88 50.40kg 18.47 67.20kg 23.05 84kg 27.64 100.8kg 32.23 117.6kg 36.81 134.4kg
Graph 3 • Joint Sensitivity: Total Body Weight Kg × Standing Height Cm Compares Normalized Fat-Free Mass Index (FFMI) when Standing Height Cm is shifted +25% (solid) vs. −25% (dashed).
0 kg/m² 30.71 kg/m² 61.42 kg/m² --- Standing Height Cm @ 75% 7.68 -30% 9.88 -15% 12.08 +0% 14.29 +15% 16.49 +30%
Summary: At 84 kg and 13.5% body fat, Lean Body Mass is 72.7 kg, raw FFMI is 22.93 kg/m², and 1.80m-Normalized FFMI is 23.05 kg/m² (92.2% of the ~25.0 natural limit).
Summary: At 84 kg and 13.5% body fat, Lean Body Mass is 72.7 kg, raw FFMI is 22.93 kg/m², and 1.80m-Normalized FFMI is 23.05 kg/m² (92.2% of the ~25.0 natural limit).
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Interactive chart & math engine powered by CalculatorGraph

Formula & Mathematical Methodology: FFMI & Natural Muscle Limit Formula

LBMkg = Weightkg × (1 − BodyFat%/100)
FFMI = LBMkg / Heightm²
NormFFMI = FFMI + 6.1 × (1.80 − Heightm)
LBM_kg = Weight_kg × (1 − BodyFat%/100); FFMI = LBM_kg / Height_m²; NormFFMI = FFMI + 6.1 × (1.80 − Height_m)
  • totalBodyWeightKg: Total Body Weight Kg (kg)
  • standingHeightCm: Standing Height Cm (cm)
  • bodyFatPercentage: Body Fat Percentage (%)

Rounding: Clinical scores round to statutory integer or decimal precision; physiological metrics round to 2 decimal places.

Worked Example: Clinical / Physiology Scenario: FFMI & Natural Muscle Limit

Compute Lean Body Mass, FFMI (kg/m²), and 1.80m-normalized FFMI from weight, height, and body fat %.

  1. Enter lab values, anthropometric measurements, or performance test metrics.
  2. Evaluate the reference equation: LBM_kg = Weight_kg × (1 − BodyFat%/100); FFMI = LBM_kg / Height_m²; NormFFMI = FFMI + 6.1 × (1.80 − Height_m).
  3. Inspect the primary classification, supporting indices, and 3 SVG charts.
Result: Computes FFMI & Natural Muscle Limit via LBM_kg = Weight_kg × (1 − BodyFat%/100); FFMI = LBM_kg / Height_m²; NormFFMI = FFMI + 6.1 × (1.80 − Height_m).

Frequently Asked Questions

How does the FFMI (Fat-Free Mass Index), Normalized FFMI & Casey Butt Muscular Potential Calculator compute its result?

It evaluates LBM_kg = Weight_kg × (1 − BodyFat%/100); FFMI = LBM_kg / Height_m²; NormFFMI = FFMI + 6.1 × (1.80 − Height_m) directly in your browser and updates three custom SVG visualizations in real time.

Can I use Goal Seek to solve backwards for a target lab value or pace?

Yes. Click "🎯 Goal Seek" in the results toolbar to solve backwards for any numeric input parameter.

Are my health and biometric inputs kept private?

Yes. All calculations run 100% locally on your device with zero external transmission.

Health & Fitness · Strength, Hypertrophy & Anthropometry

FFMI (Fat-Free Mass Index), Normalized FFMI & Casey Butt Muscular Potential Calculator: inputs, method, and how to read the result

Compute Lean Body Mass, FFMI (kg/m²), and 1.80m-normalized FFMI from weight, height, and body fat %.

Choose inputs for the case you are checking

The defaults are illustrative. Replace them with values for your case and keep the units shown beside each field.

  • Total Body Weight Kg: Total body weight in kilograms.
  • Standing Height Cm: Standing height in centimeters.
  • Body Fat Percentage: Estimated body fat percentage (%).

What the calculation includes

With the default values shown, Normalized Fat-Free Mass Index (FFMI) is 23.05 kg/m². The calculation follows FFMI & Natural Muscle Limit Formula; the formula and variable definitions above show how the inputs combine.

One-input check: With the other defaults held constant, changing Total Body Weight Kg from 84 kg to 92 kg changes Normalized Fat-Free Mass Index (FFMI) from 23.05 kg/m² to 25.24 kg/m². This is a comparison inside the calculator's stated model, not a prediction.

Where to use caution

  • Uses peer-reviewed clinical and sports physiology formulas.
  • For educational and informational reference only; clinical scores do not replace physician judgment or laboratory reference ranges.

Scope: Global Clinical & Sports Science Consensus Check the assumptions and limitations against your situation before relying on the estimate.

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