Estimate arm size from wrist size with a 2.28 × wrist rule of thumb, see wrist-and-ankle body proportions, or calculate your current FFMI.

Uses a 2.28 × wrist rule of thumb; it is not a validated limit on muscle size.

Optional settings

Muscle Potential Formula

Choose Arm size from wrist size to apply this site-defined circumference example. Choose Wrist size from arm size for its inverse. It is arithmetic only, not a validated prediction of individual arm size or natural muscle mass.

MP = WS × 2.28

Variables:

  • MP is the illustrative flexed upper-arm circumference (inches)
  • WS is the wrist circumference (inches)

The multiplier 2.28 and the legacy chart coefficients are retained site-defined examples without established independent primary-source validation. They are not attributed to a researcher and should not be treated as personal targets. Chart circumferences use arm = 2.28w, forearm = 1.83w, neck = 2.30w, chest = 3.15w + 2.54a, thigh = 2.65a and calf = 1.80a, where w and a are wrist and ankle circumferences in the same unit.

What is Muscle Potential?

The page title does not imply a validated muscle-potential prediction. Circumference outputs are illustrative only. Current FFMI = weight in kg × (1 − body fat/100) ÷ height in m²; fat-free mass includes more than muscle. The retained height adjustment is FFMI + 6.1(1.8 − height in m), as documented in Trexler et al. (2017); the indexed Kouri abstract reports 6.3. This tool applies no universal natural-limit threshold or health/drug-use classification.

How to Calculate Muscle Potential?

The following steps calculate the illustrative arm proportion from wrist circumference. They do not predict future growth.

  1. First, measure your wrist circumference (WS) in inches (or enter it in cm/mm and let the calculator convert it).
  2. Next, use the formula MP = WS × 2.28.
  3. Finally, calculate the illustrative flexed upper-arm circumference (MP) in inches (or select centimeters).
  4. After inserting your wrist size and calculating the result, check your answer with the calculator above.

Example Problem :

Use the following variables as an example problem to test your knowledge.

wrist size (WS) = 6.5 inches

Using the factor = 2.28

illustrative arm circumference (MP) = 6.5 × 2.28 = 14.82 inches