Shoulder width in bodybuilding is measured across the widest point of your deltoid muscles, not your skeleton. This “bideltoid” measurement captures the muscle mass you’re actually building, and for most men it averages around 18 inches before serious training. Here’s how to take the measurement correctly, track it over time, and use it to gauge your proportions.
Two Measurements, Two Purposes
There are two distinct ways to measure shoulder width, and they tell you different things. The first is biacromial width: the distance between the outermost points of your acromion processes, the bony tips of your shoulder blades. This is your skeletal frame width. It’s largely genetic and doesn’t change with training. It’s useful for understanding your bone structure but not for tracking muscle growth.
The second is bideltoid width: the distance between the most prominent points of your left and right deltoid muscles. This is the measurement bodybuilders care about because it reflects actual muscle development. As your lateral and rear delts grow, this number increases. When someone in a bodybuilding context says “shoulder width,” they almost always mean bideltoid.
How to Measure Bideltoid Width
You’ll need a partner and a flexible, non-stretchable tape measure. Stretchy sewing tapes can add a quarter inch of error over time, so use a fiberglass or cloth tape that holds its length.
Stand with your arms relaxed at your sides, posture upright but not forced. Don’t puff your chest or pull your shoulders back harder than normal. Have your partner stand behind you and stretch the tape across your back from the outermost point of one deltoid to the outermost point of the other. Measuring across the back rather than the front tends to be more accurate because the tape follows the contour of your shoulders more naturally. The tape should be taut and level, not draped or angled.
The outermost point of your deltoid is roughly where the lateral head is thickest, usually a couple of inches below the acromion. Your partner should look for the widest horizontal line across your shoulders and measure there. Take three readings and average them to reduce error.
Measuring Biacromial Width
If you also want your frame measurement, the landmark is the acromion process on each side. You can find it by running your fingers along the top of your shoulder toward your arm. It’s the bony ridge where the back of your shoulder meets the top of your arm. Have your partner place the tape (or a straight edge) from the outermost edge of one acromion to the other. This number typically falls between 14 and 16 inches for most men and won’t change with training.
How to Measure Solo
If you don’t have a training partner handy, the wall method works reasonably well. Stand with your back flat against a wall, head up, shoulders relaxed, feet about shoulder-width apart. Reach across your body with your right hand and make a light pencil mark on the wall where your left shoulder is widest (for bideltoid) or where the bony tip sits (for biacromial). Repeat on the other side with your left hand. Then step away and measure the distance between the two marks with a tape measure or yardstick.
This method is less precise than having someone measure you directly because reaching across your body can shift your shoulder position slightly. If you tape sheets of paper to the wall first, you avoid marking the paint and can keep old sheets as a visual record. For consistency, always mark the same type of measurement (bideltoid or biacromial) and stand in the same spot.
Shoulder Circumference for Tracking Growth
Many bodybuilders also track shoulder circumference, which wraps the tape all the way around your shoulders and chest at the level of the deltoids. Data from a large U.S. Army anthropometric survey puts the average male shoulder circumference at about 40.7 inches. This measurement captures front, side, and rear delt mass along with upper chest thickness, so it’s a useful complement to bideltoid width when you want a fuller picture of upper body growth.
To take it, loop a non-stretchable tape around your torso at the widest point of your shoulders, passing over the top of your deltoids and across your upper chest. Keep the tape level all the way around. Again, arms relaxed at your sides, no flaring.
The Golden Ratio Target
Bodybuilding aesthetics aren’t just about raw size. The classic physique ideal is built around the shoulder-to-waist ratio, often called the Adonis Index. The target ratio is approximately 1.618, derived from the golden ratio that appears throughout nature and classical art. To calculate yours, measure your shoulder circumference and divide it by your waist circumference at the navel.
For example, if your shoulder circumference is 48 inches and your waist is 30 inches, your ratio is 1.6, which is nearly the ideal. A 32-inch waist would need roughly 51.8 inches of shoulder circumference to hit 1.618. This ratio matters because physique judges and casual observers both respond to the V-taper it creates. You can chase the ratio from either direction: building your delts wider or leaning out your waist.
Tips for Consistent Tracking
Small inconsistencies compound over months of tracking. Circumference and breadth measurements are more prone to error than something like height or weight, so building a repeatable routine matters.
- Same time of day. Measure in the morning before training. A post-workout pump can add a half inch or more to your shoulders temporarily.
- Same person measuring. Different partners will place the tape slightly differently. If you switch, re-baseline your numbers.
- Same tape measure. Cheap tapes stretch over time. Use a fiberglass anthropometric tape and replace it yearly.
- Same posture. Stand the same way every time: arms down, shoulders relaxed, not flexed. Even a slight shrug shifts the reading.
- Three-reading average. Take three measurements, drop any obvious outlier, and record the average. This smooths out the small positioning differences between reps.
Track your numbers monthly rather than weekly. Deltoid hypertrophy is visible on a tape measure over four to eight week windows, not day to day. If your bideltoid width increases by even half an inch over two to three months of focused lateral delt work, that’s meaningful progress.