How to Sew a Beanie Helmet Liner From a T-Shirt

person wearing a red beanie helmet liner
Mollie Johanson
Overview
  • Total Time: 60 mins
  • Skill Level: Intermediate
  • Estimated Cost: $10

Why buy a helmet liner when you can make one out of a T-shirt? This beanie-style cap protects your head and hair under a motorcycle helmet, bike helmet, or hard hat. It also can be an extra layer under another hat. Plus, you can even wear it on its own. By using a T-shirt, you can make this beanie in a flash. The project should take intermediate sewers about an hour to complete. And you don't even need a serger because the T-shirt creates the finished hem of the hat. Plus, with a few simple adjustments, it's easy to make this hat in any size you need.

Tip

Instead of a T-shirt, you can use other knit fabric. But you will need to do a bit more finishing for the hem.

What You'll Need

Equipment / Tools

  • Tape measure
  • Rotary cutting tools
  • Pins
  • Sewing machine
  • Paper plate (or another 9 1/4-inch circle template)

Materials

  • T-shirt
  • Matching thread

Instructions

  1. Measure and Cut the T-Shirt

    First, measure the head of the person who will wear the beanie. Measure around from the forehead to the top of the neck. Add 1/2 inch to the measurement. This average-size hat starts with a 24-inch measurement.

    Cut a piece 8 inches wide and the length of the head measurement from the bottom of the T-shirt, so the hem is the bottom of the long edge. The easiest way to do this is to lay the shirt flat, cutting the piece on the fold to half the head measurement. 

    Knit fabrics, especially pre-washed T-shirts, often have a little twist. Don't worry if you find this in the shirt you're using, as it won't affect the hat.

    measuring T-shirt for beanie
    The Spruce / Mollie Johanson
  2. Sew the First Seam

    Sew the rectangle into a tube with a French seam for added strength. To do this, fold the rectangle, matching the short edges with the wrong sides together. Pin the fabric, and sew along the short edge with a scant 1/4-inch seam allowance.

    sewing rectangle into a tube
    The Spruce / Mollie Johanson
  3. Finish the Back Seam of the Hat

    Turn the tube wrong side out. Pin and sew the seam again with a 1/4-inch seam allowance (or slightly larger if needed to encompass the first seam). If possible, verify that the tube fits the wearer's head at this point. Then, lay the tube flat with the seam centered. 

    finishing the back seam
    The Spruce / Mollie Johanson
  4. Mark and Cut the Shaping

    Fold a large paper plate in quarters. You can also use a paper circle template from a dinner plate that's at least 9 inches in diameter.

    Use the folded plate to cut curves on each side of the top of the tube.

    cutting the curves
    The Spruce / Mollie Johanson
  5. Sew the Curved Top of the Helmet Liner

    Pin the curves and top edge. Sew the top of the hat together with a 1/4-inch seam allowance. Back stitch at the beginning and end, making sure the sewing reaches the edges of the folded sides.

    Turn the hat right side out, and try it on.

    Sew the Curves on the Hat
    The Spruce / Mollie Johanson

T-Shirt Beanie Tips and Ideas

  • Instead of a close-fit helmet liner, make this into a slouchy beanie by cutting the initial rectangle to 10 inches tall or more.
  • For a snugger fit, use a larger circle template. 
  • All-over print T-shirts make great caps with lots of decoration.
  • For a warmer helmet liner, make this out of anti-pill fleece and hem the bottom.
DIY T-shirt beanie
The Spruce / Mollie Johanson