Arm Muscle Area (AMA) Calculator

About this calculator

Arm Muscle Area (AMA) is a nutrition-screening measurement calculated from just two numbers — mid-upper arm circumference (MUAC) and triceps skinfold thickness — using the formula AMA = [(MUAC − π × triceps skinfold)²] / (4π), which mathematically strips the subcutaneous fat ring off the arm to isolate the muscle-plus-bone cross-section. A “corrected” version subtracts a further estimate for bone area to isolate muscle alone, and converting that back into a circumference gives Arm Muscle Circumference.

Clinicians and dietitians use AMA as a quick bedside proxy for lean tissue and nutritional status when a DEXA scan or MRI isn't available — a low or declining AMA in a hospitalized or elderly patient is a red flag for malnutrition or muscle wasting (sarcopenia), since it can be tracked over time with nothing more than a measuring tape and skinfold calipers.

This calculator takes your mid-upper arm circumference and triceps skinfold and returns your arm muscle area, corrected arm muscle area and arm muscle circumference.