Fat Percentage Calculator

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Fat Percentage Calculator
MaleFemale
Results:
Please enter your measurements to see results.
function toggleHip(){var gender=document.getElementById('gender').value;var hipRow=document.getElementById('hipRow');if(gender==='female'){hipRow.style.display='table-row';}else{hipRow.style.display='none';}}function calculateFat(){var gender=document.getElementById('gender').value;var w=parseFloat(document.getElementById('weight').value);var h=parseFloat(document.getElementById('height').value);var n=parseFloat(document.getElementById('neck').value);var wa=parseFloat(document.getElementById('waist').value);var hi=parseFloat(document.getElementById('hip').value);var showSteps=document.getElementById('showSteps').checked;if(isNaN(w)||isNaN(h)||isNaN(n)||isNaN(wa)||(gender==='female'&&isNaN(hi))){alert('Please enter valid measurements.');return;}var bf=0;if(gender==='male'){bf=86.010*Math.log10(wa-n)-70.041*Math.log10(h)+36.76;}else{bf=163.205*Math.log10(wa+hi-n)-97.684*Math.log10(h)-78.387;}var fatMass=(w*(bf/100));var leanMass=w-fatMass;var category="";if(gender==='male'){if(bf<6)category="Essential Fat";else if(bf<14)category="Athletes";else if(bf<18)category="Fitness";else if(bf<25)category="Average";else category="Obese";}else{if(bf<14)category="Essential Fat";else if(bf<21)category="Athletes";else if(bf<25)category="Fitness";else if(bf<32)category="Average";else category="Obese";}var resultHtml='
Body Fat: '+bf.toFixed(1)+'%
';resultHtml+='
Category: '+category+'
';resultHtml+='
';resultHtml+='Fat Mass: '+fatMass.toFixed(1)+' lbs
';resultHtml+='Lean Body Mass: '+leanMass.toFixed(1)+' lbs
';resultHtml+='
';if(showSteps){resultHtml+='
Method: U.S. Navy Body Fat Algorithm
Note: Formulas are based on regression equations using log10 of body circumferences. Accuracy is typically +/- 3%.
';}document.getElementById('answer').innerHTML=resultHtml;}function resetCalc(){document.getElementById('answer').innerHTML='Please enter your measurements to see results.';document.getElementById('hipRow').style.display='none';}

Calculator Use

The fat percentage calculator is a vital tool for anyone looking to track their health and fitness progress beyond simple weight monitoring. While scales show total body mass, this calculator estimates the percentage of that weight comprised of adipose tissue (fat) versus lean mass (muscle, bone, and organs).

To get an accurate result, you should use a flexible measuring tape and measure at the following points:

Neck
Measured just below the larynx, sloping slightly downward to the front.
Waist
For men, at the navel; for women, at the narrowest point of the abdomen.
Hips (Women only)
Measured at the widest horizontal point of the buttocks.

How It Works

This fat percentage calculator utilizes the U.S. Navy Method, which is one of the most reliable circumference-based estimation techniques. It uses logarithmic equations to correlate body measurements with total density.

Male Formula: %BF = 86.010 × log10(Waist – Neck) – 70.041 × log10(Height) + 36.76

Female Formula: %BF = 163.205 × log10(Waist + Hip – Neck) – 97.684 × log10(Height) – 78.387

  • Log10: The base-10 logarithm used to smooth out the variance in body shapes.
  • Circumference: Measurements should be taken on bare skin for maximum precision.
  • Height: Measured without shoes, standing tall against a flat surface.

Calculation Example

Example: A male athlete weighs 190 lbs, stands 72 inches tall, has a 33-inch waist and a 16-inch neck.

Step-by-step solution:

  1. Calculate Waist – Neck: 33 – 16 = 17 inches.
  2. Apply the logarithm: log10(17) &approx; 1.230.
  3. Apply the height logarithm: log10(72) &approx; 1.857.
  4. Plug into formula: (86.010 × 1.230) – (70.041 × 1.857) + 36.76.
  5. Result = 105.79 – 130.06 + 36.76 = 12.49% Body Fat.

Common Questions

Why is body fat percentage more important than BMI?

Body Mass Index (BMI) only accounts for weight and height. It cannot distinguish between muscle and fat. A muscular individual might be classified as "overweight" by BMI, but our fat percentage calculator would reveal they have a healthy, low body fat level.

How often should I check my body fat?

Because body fat changes more slowly than water weight, it is best to check your percentage every 2 to 4 weeks. Checking daily can be discouraging due to minor measurement errors or temporary bloating.

What is a "healthy" body fat range?

For men, 10-20% is generally considered healthy and fit. For women, 18-28% is the typical healthy range. Essential fat (the minimum needed for survival) is roughly 3-5% for men and 10-13% for women.

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