A snug bike helmet fit is key if the helmet is to do the job of protecting you in an accident. Like sneakers, helmets are made on different molds that vary among brands. Unlike shoes, though, there are no standard “measurements” in helmet sizing. Most helmets list a measurement of the head circumference it will fit. This can help narrow the options, but your head might be a medium from one maker and a small from another.

Most of the models we tested come in a single “universal” shell size while other adult bike helmets, including the top-rated Scott Arx Plus ($125) come in multiple sizes. The goal is to find the helmet that fits your specific head shape as closely as possible and requires few if any pads to achieve a snug fit. The best way to do this is to go to a bicycle shop and try on different brands and different helmets within brands. “Try on the size you think you need, and then try a size smaller,” says Rich Handel, Consumer Reports' assistant test project leader. (Warning: Don’t be tempted to buy a larger size for your child, thinking she will grow into it!) If you wear a hat under your helmet, or put your hair in a ponytail, make sure your head is ride-ready before you go helmet shopping. If you’re buying a bike helmet online, check the return policy to make sure you can exchange it.

If you ride a comfort bike or a cruiser that puts you in an upright position, you might be fine with a less-expensive mid-weight helmet. If you ride a racing bike with dropped handlebars in an aerodynamic position, consider a lightweight model that may decrease the strain on your neck muscles during day-long rides at high speeds. Another factor that’s especially important to performance riders is ventilation—rated by our testers at 20 mph on a motorized bicycle. Mountain bikers should consider a helmet with a removable visor to protect for your face against branches or other hanging obstacles.

Follow our tips to make sure you get the best bike helmet fit for you.

Check the Fit

  • The helmet must be level on your head.
  • The front edge should be no more than an inch or so above your eyebrows.
  • The strap should fit closely under your chin.
  • Straps should meet just below your jaw and in front of your ears, forming a V under your earlobes.

How Do You Know Whether the Helmet Fits?

Push the helmet side to side, then front to back, and give it a twist. (The skin at your temples should wrinkle.) The helmet should move only a little bit.

If it’s too loose and your helmet has an adjuster knob, tighten it, or if your helmet came with extra pads, use the thicker ones. If it’s too tight, turn the knob to loosen it or use the thinner pads.

Will It Stay Put While You’re Riding?

With the heel of your hand, push up on the front edge of the helmet. If it exposes your forehead, shorten the front straps. Then grab the back and try to push the helmet forward off your head. If it covers your eyes, shorten the back straps.

You’ll know the chin strap is tight enough when you open your jaw halfway and feel the helmet press down on your head.

Getting a good bike helmet fit and then wearing your helmet every time you ride is just one part of bicycling safety. Follow the rules of the road and make sure you are visible to drivers. The safest move is to avoid an accident in the first place.