The over-arm measurement wraps a tape measure around the widest part of your upper body, including your arms, to determine your suit jacket or tuxedo size. It differs from a standard chest measurement because it accounts for the bulk of your arms pressed against your torso, giving a more accurate picture of how a jacket will actually fit across your frame.
What the Over-Arm Measurement Captures
A standard chest measurement goes around your ribcage, usually just under the armpits. The over-arm measurement sits higher and wider. It circles the broadest point of your chest, shoulders, and upper arms all at once. This matters because a jacket doesn’t just drape over your chest; it has to accommodate the full width of your arms when they hang naturally at your sides. Two people with the same chest size can have very different over-arm measurements depending on their shoulder width and arm muscle.
How to Take the Measurement
You’ll need a soft, flexible tape measure (the kind used for sewing, not a retractable metal one). Having a second person help makes this significantly easier and more accurate, since reaching around your own body can shift your posture and skew the reading.
Stand upright with your arms relaxed and hanging straight down at your sides. Don’t puff out your chest or pull your shoulders back. Breathe normally and take the reading at the end of a natural exhale, not while holding a deep breath.
The person measuring should wrap the tape around the fullest part of your upper body. This means the tape passes across the broadest point of your chest in front, over the thickest part of each upper arm, and across your shoulder blades in back. Keep the tape level on both sides so it doesn’t dip or ride up. It should be snug enough to stay in place but not tight enough to compress your arms or clothing. Read the number where the tape overlaps.
If you’re measuring yourself, stand in front of a mirror to check that the tape is level. Pass the tape around your body, hold both ends in front, and adjust until it sits flat without twisting.
Common Mistakes to Avoid
The most frequent error is measuring too low. If the tape slips down to mid-chest level, you’re getting closer to a chest measurement than an over-arm measurement. The tape should cross the peak of each bicep, not the lower part of your arm.
Wearing a thick sweater or bulky shirt will inflate the number. Measure over a dress shirt or thin layer, since that’s what you’ll typically wear under a jacket. Pulling the tape too tight is another issue. You want the tape to make contact all the way around without digging in. If it leaves a mark on your skin or bunches the fabric of your shirt, loosen it slightly.
Over-Arm Size and Jacket Size
Suit manufacturers use over-arm measurements to map customers to standard jacket sizes. The ranges overlap, so your reading points you toward the right ballpark rather than a single precise size. Here are some common reference points for men’s suit jackets:
- Size 36 jacket: 42 to 44 inches over-arm
- Size 38 jacket: 44 to 47 inches
- Size 40 jacket: 46 to 49 inches
- Size 42 jacket: 48 to 51 inches
- Size 44 jacket: 50 to 54 inches
- Size 46 jacket: 52 to 54 inches
- Size 48 jacket: 56 to 58 inches
- Size 50 jacket: 56 to 58 inches
- Size 52 jacket: 58 to 60 inches
Short, regular, and long versions of the same size can differ by an inch or two in the over-arm range. A 38 Short, for example, tends to run 44 to 46 inches, while a 38 Regular runs 45 to 47. If your measurement falls at the boundary between two sizes, the fit of the shoulders and chest will help you decide which direction to go.
Over-Arm vs. Chest Measurement
Some sizing guides ask for a chest measurement, others ask for over-arm, and mixing them up will land you in the wrong size. Your over-arm number will always be larger than your chest number, typically by 4 to 8 inches depending on your build. Someone with a 40-inch chest might measure 46 or 47 inches over-arm. If a size chart doesn’t specify which measurement it uses, check whether the numbers seem to correspond to jacket sizes directly (chest) or run noticeably larger (over-arm).
Tuxedo rentals frequently use the over-arm measurement because it’s a faster way to estimate fit for off-the-rack jackets. Custom tailors, on the other hand, usually take both measurements plus several others to get a complete picture of your proportions.
Tips for a Reliable Reading
Take the measurement two or three times and use the average. Small shifts in arm position or tape angle can change the result by an inch. If you’re ordering online and can’t try the jacket on first, rounding up to the larger size is generally safer. A slightly roomy jacket can be tailored in, but a jacket that’s too tight across the arms and shoulders is difficult to alter without replacing panels of fabric.
Body measurements can shift throughout the day. Muscles tend to be slightly pumped after exercise, and water retention can add volume later in the afternoon. For the most consistent reading, measure at the same time of day you’d normally get dressed.