Measuring the circumference of the upper arm, or bicep measurement, is a simple way to track progress toward fitness goals. This measurement monitors changes in muscle size (hypertrophy) and reflects shifts in overall body composition. Tracking this number provides objective data beyond the scale, offering a direct assessment of muscular development or fat loss. Standardizing the measuring technique is important to ensure the collected data reflects a physical change rather than a procedural error.
Preparation and Necessary Tools
Accurate measurement requires the right equipment and setup to minimize variables that could skew the results. The most important tool is a flexible, non-stretchable tape measure, such as a tailor’s tape, designed to conform smoothly to the body’s contours. A plastic or fiberglass tape is preferred over cloth as it maintains its integrity better. Always measure directly against the skin, as clothing, even thin fabric, can add circumference and produce an inaccurate reading.
For the most precise results, it is helpful to have another person take the measurement, especially when beginning to track progress. This assistance allows the individual to maintain the correct posture and muscle relaxation without manipulating the tape measure simultaneously. Before starting, ensure the arm is bare and remove any constricting items like tight watch bands or bracelets. This isolates the arm circumference without external factors adding bulk to the measurement.
The Standard Relaxed Measurement
The standard relaxed bicep measurement is the most reliable method for tracking objective changes in muscle mass and body composition. To begin, stand upright with your arm hanging naturally at your side, completely relaxed, without tension in the muscles. The palm should face forward or slightly toward the body, maintaining a neutral position. Finding the correct anatomical landmark is the next step for consistency.
The measurement should be taken at the midpoint of the upper arm. This point is halfway between the bony protrusion on the top of your shoulder (the acromion process) and the point of your elbow (the olecranon). Many protocols recommend locating and marking this midpoint with a pen to ensure the tape measure is placed in the exact same spot every time. Wrap the flexible tape measure around this marked midpoint, ensuring it is perfectly level around the circumference of the arm.
The tape must be snug against the skin but not so tight that it compresses the underlying tissue, which would artificially reduce the number. Since most people have a slight size difference between their dominant and non-dominant arms, it is beneficial to measure both, but you should select one to consistently track for long-term progress. This relaxed circumference provides the truest representation of your arm’s baseline size, including both muscle and fat tissue.
The Flexed Measurement
In contrast to the relaxed measurement, the flexed measurement gauges the maximum size and peak development of the biceps muscle belly. To perform this measurement, you must first bend your arm at a 90-degree angle, positioning your forearm parallel to the floor. Next, rotate your hand so the palm is facing up (supination), and fully contract the bicep muscle as hard as possible. The goal is to create the maximum possible peak.
While maintaining this contraction, wrap the tape measure around the highest point of the muscle peak. This point is typically slightly higher on the arm than the midpoint used for the relaxed measurement. The tape must be kept level and remain flush against the skin without digging into the muscle. This measurement yields a larger number than the relaxed measurement due to muscle contraction, reflecting peak muscular size and shape rather than baseline body composition.
Ensuring Accuracy for Tracking Progress
Achieving consistent results depends on controlling external factors that can temporarily influence arm size. One important factor is the time of day; measurements should always be taken at the same time, such as first thing in the morning. This consistency helps eliminate the temporary size increase that occurs after a workout, known as a “pump,” where blood is rushed to the muscle tissue.
Hydration and feeding status also play a role in arm circumference. Ideally, the measurement should be taken before consuming a meal or large amounts of water. Always measure the same arm (dominant or non-dominant) and use the same physical reference point, such as the marked midpoint or the absolute peak of the bicep. By rigorously controlling these variables, you ensure that any change in the recorded number represents genuine physical progress rather than simple daily fluctuations.