How to Measure Arm Width

• Stand with your arms naturally at your sides.
• Have a friend wrap a fabric tape measure around the thickest part of your bicep.
• This measurement is your arm width.

Measuring around Your Bicep

Ask someone to help you measure your arm width. It is very awkward and difficult to try measuring around your own biceps. Ask a friend or family member to help you out, it will only take a minute or two! If you don’t have anyone who can help you measure your arm width, you can get all your measurements taken for free at most clothing stores that sell dress clothes.

Stand with your arms hanging naturally at your sides. Stand up straight and let your arms hang down loosely. Don’t force them straight or bend them upwards at all, just let them hang all on their own.Tip: Don’t wear thick clothing or multiple layers. A single shirt is fine and won’t throw off the measurement, but remove any extra layers like sweaters or jackets to get an accurate number. Your arms will have a slight natural bend at the elbow when you stand straight with your arms completely loose at your sides. Don’t flex, either. Always take your arm width measurements with your arms totally relaxed.

Have your helper wrap a flexible tape measure around your bicep. Have them place the end of a flexible tailor’s tape measure against the middle of the outside of your arm, at the thickest point of your bicep. Tell them to wrap the tape measure all the way around your arm until it doubles back on itself. Always measure around the thickest part of your arm to get accurate arm width measurements.

Read the numbers and lines on the tape measure to find out your bicep width. Look at the line on the tape measure exactly where it starts doubling back on itself. The lines are decimal fractions of a full centimeter or inch, so count the lines and add them to the number just before as a decimal to get your arm width. For example, say your tape measure is in centimeters. If the number right before the tape measure doubles back on itself is 32 and there are 5 lines after it before the tape measure touches the beginning of the numbers, then your arm width is 32.5 cm (12.8 in).

Finding the Sleeve Width of a Shirt

Lay a shirt out on a flat surface with the arms spread out smoothly. Button up the shirt if it has buttons and lay it down on a table or the floor. Spread the arms out flat and smooth them out with your hands so that there are no wrinkles or creases. You can do this with any shirt if you just want to know the sleeve width to purchase a similar shirt. Or, if you want to use a shirt to find your approximate arm width, choose a shirt that fits very closely around your upper arms.

Use a measuring tape to measure across the middle of the upper arm sleeve. Place the end of the tape measure at the top edge of the upper arm sleeve, approximately where your bicep would go. Stretch the tape measure out flat across the sleeve to the bottom edge.Tip: A flexible tailor’s measuring tape is best for this. However, if you don’t have one you can use a standard stiff tape measure. If you do, make sure you press it down as tightly as you can against the shirt. Make sure you aren’t measuring right next to the shoulder or where the sleeve starts to narrow for the forearm. The best place to measure is usually about 15–18 cm (5.9–7.1 in) from the seam where the sleeve attaches to the arm hole.

Read the measuring tape to get half of the sleeve width. Look at the number and lines at the bottom edge of the shirt sleeve. Add the lines as decimal points to the number just above the bottom edge of the sleeve, if it is not an exactly even number, to know what half of the sleeve’s width is. For example, if you are reading a measuring tape in inches, and the number just above the bottom edge of the sleeve is 6 with 2 lines below it where it meets the edge of the sleeve, then half of the sleeve’s width is 6.2 in (16 cm).

Double the number to get the full sleeve width or your approximate arm width. Multiple the measurement you got from the tape measure by 2 to get the total circumference of the sleeve. Use this to buy a shirt of the same size or to know your approximate bicep size if you chose to measure a shirt with tight-fitting sleeves. For instance, if the half sleeve width measurement was 6.2 in (16 cm), the total circumference of the sleeve would be 12.4 in (31 cm).