Hats for cancer patients, or "chemo caps," provide warmth for patients who lose their hair during chemotherapy. With a small amount of yarn, you can knit a hat for a friend undergoing chemotherapy, or to donate to a charitable organization. A basic hat pattern is adaptable for any size, adult or child, by changing the size of needles used.
Choose a soft yarn. After losing her hair, a patient's scalp is tender, so a soft yarn is important. In addition, chemotherapy patients are often sensitive to wool, so choose a cotton, cotton-blend or synthetic yarn.
Pick a circular needle in an appropriate size for the yarn. The information on the yarn's ball band includes the recommended needle size.
Cast on enough stitches on the double-pointed needles (DPNs) to make a tube about 5 inches around. Consult the ball band for the stitches per inch for an approximate number. Join the stitches into a round, and knit for about 4 inches. Cast off. This is your gauge swatch.
Measure around the swatch with the tape measure. To determine the number of stitches per inch, divide the number of stitches you cast on by the circumference of the swatch. For example, if you cast on 30 stitches, and the swatch is 5 inches around, the stitch gauge is 6 stitches per inch.
Measure around the patient's head at the point where the brim will be. Also measure from this point to the crown of the head to determine the height of the hat. The hat should cover her entire head. If you cannot measure her head, a small adult has a head size of around 20 inches and a crown height between 6 1/2 and 7 1/2 inches, according to "Knitting Rules" by Stephanie Pearl-McPhee.
Multiply the stitches per inch by the circumference of the her head to determine how many stitches to cast on. A chemo cap should fit snugly, so do not add any ease to the measurement. For example, if her head measures 19 inches around, and the stitch gauge is 6 stitches per inch, your cast on is 114 stitches. If you get an odd number, add one more stitch.
Knit the Hat
Cast the number of stitches calculated onto the circular needle. Join the stitches into a round, making sure not to twist the stitches. Put a safety pin on the stitch at this point to show the beginning of the round.
Start the hat with a knit one, purl one ribbing. Continue with this stretchy and comfortable ribbing for about 2 inches.
Change to stockinette stitch, by knitting every stitch until the total length of the hat equals the crown height.
Decrease evenly around, starting at the safety pin. To decrease evenly, choose a number that divides evenly into your number of stitches. For example, six goes into 114 evenly, so to decrease evenly knit four stitches and knit two stitches together. This is a decrease round.
Knit one round evenly, with no decreases.
Knit one decrease round, followed by an even round until you have only a few stitches left. Change to the DPNs when there are too few stitches to reach around the circular needle.
Break the yarn, leaving a 12-inch tail. Thread the tail through a tapestry needle. Draw the needle through the last stitches, and draw the top of the hat together snugly.
Weave in the ends. Wash and block the hat before giving it to the patient, as washing softens the yarn.
Consider making several hats to go with her wardrobe. If you enjoy making hats, check your local hospital for charities that accept hand-knit chemo caps.