How to Measure Cap Size Step by Step

Understanding Cap Sizing Basics

Cap sizing is an essential skill for anyone who wants to wear hats that fit properly and look good. A poorly fitting cap can be uncomfortable, slip off your head, or sit awkwardly on your face. Understanding how cap sizing works begins with knowing that most caps are sized using a numerical system based on head circumference measured in inches or centimeters. Unlike clothing sizes that vary dramatically between brands, cap sizes follow a more standardized approach, though variations still exist between manufacturers.

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The most common sizing system in the United States uses measurements ranging from approximately 6 5/8 inches to 8 inches in circumference, which translates to sizes labeled as XS, S, M, L, XL, and XXL. Some brands use numerical sizing instead, such as 54, 55, 56, 57, 58, 59, and 60 centimeters. International brands may use different systems entirely. For example, European sizing often relies on centimeter measurements, while some specialty hat makers use fractional sizes like 6 7/8 or 7 1/4.

The difference between consecutive sizes might seem small—often just 1/8 inch or about 3 millimeters—but this small variation can significantly impact comfort and fit. A cap that is a quarter inch too small can create uncomfortable pressure across your head, while one that is a quarter inch too large will rotate and slip. Understanding these basics helps you navigate the sizing systems you'll encounter when shopping for caps either in stores or online.

Practical Takeaway: Before measuring, familiarize yourself with the sizing system your preferred cap brand uses. Check their size chart, as this will guide you on whether they measure in inches, centimeters, or use letter sizes.

Gathering Your Measurement Tools

Accurate cap sizing requires only a few simple tools, most of which you likely already have at home. The most important tool is a soft measuring tape—the flexible kind used in sewing or tailoring. These tapes are typically made of fabric or plastic with printed measurements and are far superior to rigid measuring tools like metal rulers or wooden yardsticks. A soft measuring tape costs between $3 and $8 at most fabric or craft stores and can last for years.

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If you don't have a soft measuring tape, you can substitute it with a piece of string or thin rope, along with a ruler or measuring stick. Simply wrap the string around your head where a cap would sit, mark where the string overlaps, and then lay it straight against a ruler to get your measurement. This method is less convenient than using an actual measuring tape but produces accurate results when done carefully.

Beyond the measuring tape itself, you'll need a few additional items: a mirror or reflective surface to see what you're doing, a pencil or marker if you're using the string method, and optionally a notebook to write down your measurements. Some people find it helpful to have another person assist with measuring, as it can be tricky to hold the tape in place while reading it accurately. However, measuring yourself is entirely possible with practice and patience.

Environmental factors matter too. Make sure you're measuring in a well-lit area where you can clearly read the tape measurements. Avoid measuring when your hair is wet or styled in an unusual way, as this can affect the result. Your hair should be in its normal, everyday state. Additionally, wear the types of hats or caps you plan to buy when taking measurements, as some people prefer to wear their caps over certain hairstyles or with specific styling that affects fit.

Practical Takeaway: Invest in an inexpensive soft measuring tape before you start. It's a one-time purchase that will serve you well for multiple cap purchases over the years and provides the most accurate and consistent results.

Finding the Correct Measurement Location

The location where you measure around your head is critical to obtaining an accurate cap size. Most cap manufacturers measure across the forehead, just above the eyebrows, and around the back of the head where the cap would naturally sit. This spot is typically about half an inch to three-quarters of an inch above your eyebrows. The measurement should go horizontally around your head in a complete circle, creating an imaginary line parallel to the ground.

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To locate this spot precisely, place your index finger on your forehead, approximately one finger-width above your eyebrows. This is where the front of the measuring tape should sit. From there, the tape should run horizontally along the sides of your head and across the back. Many people make the mistake of measuring too high on their head, near the crown, or too low, near the temples. Both of these locations produce measurements that won't match how a cap actually sits.

The back portion of the measurement is particularly important. The tape should cross the back of your head at approximately the same height as the front measurement, running around the fullest part of the back of your skull. This is usually an inch or two above the base of your skull where your neck begins. Some people have fuller backs to their heads than others, so make sure the tape follows the contour of your head naturally without being forced or repositioned.

A helpful way to verify you're measuring in the correct location is to try on any cap you currently own and note where it sits on your head. Then, place your measuring tape in the same location. You can also take a photo of yourself from the side while holding the measuring tape in place—this provides a visual reference for whether you're measuring at the right spot on future occasions.

Practical Takeaway: Mark your measurement location by placing a small piece of tape on your forehead at the eyebrow line. This creates a visual guide and helps you maintain consistency if you need to measure multiple times or remeasure at a later date.

Taking Your Measurement Accurately

Once you've located the correct measurement spot and have your soft measuring tape ready, it's time to take the actual measurement. Begin by positioning the end of the measuring tape at the center of your forehead, right at the eyebrow line. Have the tape sit flat and snug against your head, but not tight. The tape should be firm enough that it doesn't slip, but loose enough that you can comfortably fit a single finger underneath it. This tension mimics how a cap should fit—snug but not restricting circulation or causing discomfort.

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Bring the measuring tape horizontally around the right side of your head, keeping it at the same height as where it started. Continue around the back of your head, then down the left side, and finally back to the starting point at the center of your forehead. Make sure the tape doesn't twist or spiral as it goes around. The tape should remain parallel to the ground throughout the measurement. Many people accidentally angle the tape upward or downward without realizing it, which produces inaccurate results.

When the tape reaches the starting point, note where it meets or overlaps. If you're using a soft measuring tape with printed measurements, read the number where the tape meets itself. Write this number down immediately. If you're using the string method, mark the overlap point with a pencil, then measure the string against a ruler. Take your time reading the measurement—don't guess or round up or down. If the measurement falls between two marks, such as between 22 and 22.25 inches, record the exact value you see.

For the most reliable results, take your measurement three separate times on the same day and record all three numbers. If the measurements vary significantly—more than one-eighth inch apart—you may have positioned the tape differently each time. If they're consistent within one-eighth inch, average the three measurements to determine your cap size. This triple-measurement approach accounts for minor variations in how you position the tape and produces a more dependable result than a single measurement.

Practical Takeaway: Create a small record of your head measurement and store it in your phone or a notebook. Having this information readily available makes future cap purchases much faster and reduces the likelihood of ordering an incorrect size.

Interpreting Your Measurement and Finding Your Size

After obtaining your head circumference measurement, the next step is converting that number into an actual cap size. The conversion process depends on which sizing system your chosen cap brand uses. If your measurement is in inches, you'll typically subtract one-eighth inch from your total measurement to find your cap size. For example, if your head circumference is 22 and 1/8 inches, your cap size would be 22 inches. This one-eighth inch reduction accounts for the fact that caps are designed to fit slightly snugly

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