Lean Body Mass Skinfold Calculator
Enter 7-site skinfold measurements to calculate lean body mass and body fat percentage using Jackson-Pollock formula.
Diagonal fold halfway between nipple and armpit
Vertical fold 2cm right of navel
Vertical fold midline of thigh
Vertical fold back of arm, halfway between shoulder and elbow
Diagonal fold 2cm below shoulder blade
Diagonal fold just above hip bone
Vertical fold on midaxillary line at nipple level
How accurate are skinfold measurements for body fat?
With proper technique, 3-site skinfold has ±3-4% accuracy vs DEXA. 7-site Jackson-Pollock (used here) has ±2-3% accuracy. Key factors: Same trained technician, same caliper (Harpenden > Lange > Accu-Measure), consistent location, right tension. Measurements should be taken on right side of body. Retest at same time of day (morning fasted ideal).
Which skinfold sites are measured?
Men (7 sites): Chest, Abdominal, Thigh, Triceps, Subscapular, Suprailiac, Midaxillary. Women (7 sites): Triceps, Abdominal, Thigh, Suprailiac, Subscapular, Midaxillary, Lower calf. The formula converts sum of skinfolds to body density, then uses Siri equation to calculate % fat and lean mass.
Why measure lean mass instead of just weight?
Lean mass (muscle + bone + organs + water) determines metabolic rate, strength, and health outcomes. Two people at 180 lbs: One with 140 lbs lean mass (athletic), another with 120 lbs (skinny fat). Same weight, vastly different health. Tracking lean mass > weight for athletes, bodybuilders, and aging adults losing muscle.
How often should I measure skinfolds?
Every 4-6 weeks for body composition tracking. More frequent (weekly) won't show meaningful change. Take measurements at same time of day (morning fasted ideal), same technician, same caliper. Track trends over 3-6 months. If lean mass drops >2 lbs/month, increase protein/calories. If body fat rises >1%/month, adjust diet.