All bike helmets sold in the U.S. must meet safety standards set by the Consumer Product Safety Commission and have a label saying the helmet meets these standards. Consumers can usually find this label on the liner inside of the helmet, on the exterior surface, or attached to the chinstrap, according to the CPSC. (A 2019 investigation by CR found that some off-brand helmets sold online do not meet these standards.)

At Consumer Reports, we evaluate helmets for ventilation, fit adjustments, ease of use, and other features. We also conduct rigorous, hands-on tests to see exactly how each helmet would fare in a crash.

In our tests we strap helmets onto head forms and use an apparatus that drops the helmets at about 14 mph onto a flat anvil to find out how well they withstand impact. An electronic sensor inside the head form monitors the force that would be transmitted to a rider’s skull in a crash.

We also test the strength of the chinstraps, attachment points, and buckles to make sure that a helmet will stay on your head and in position during a crash. We drop an 8¾-pound weight 2 feet so that it yanks on the straps to simulate the force that might occur in a crash.

Remember: A bike helmet should be replaced approximately every five years, or sooner if it is damaged. If the helmet has been involved in a crash, replace it, even if it does not appear to be damaged. The expanded polystyrene foam that dissipates the energy from the impact may still look intact, but bike helmets are designed to do the job just once.

Bike helmets are designed and tested for their ability to protect against severe head injury, such as a skull fracture. But there are a few different helmet technologies that aim to reduce rotational force, which correlates to how much the brain moves inside the skull in the event of an impact and is thought to be a factor in concussions. There are many of these systems, including Multi-directional Impact Protection System (MIPS) and WaveCel.

MIPS, the most widely known of these technologies, is a thin, low-friction liner inside the helmet that allows the outer shell to slide a few millimeters across the skull on impact, reducing rotational force and the amount of energy transferred to the head. It was first released in a cycling helmet in 2010 and can now be found inside hundreds of different helmets made by companies including Bell, Cannondale, Giro, and Trek.

In our earlier tests of two pairs of the same brand and model helmets—one MIPS, one not—the MIPS helmets reduced rotational force up to 43 percent compared with the non-MIPs helmets. The MIPS helmets cost around $20 more than non-MIPS versions of the same model.

Instead of a sliding component, helmets with WaveCel have an internal layer made of a malleable plastic that forms a sort of three-dimensional mesh. It’s designed to crumple, flex, and glide sideways at the moment of impact, functioning like a suspension system to absorb the rotational force from the impact.

Both technologies are comparable in reducing the risk of brain injury, according to researchers at the Virginia Tech Helmet Lab, but it’s difficult to prove that any helmet will protect against concussion because there’s no single objective test, such as a CT scan or an MRI, that can determine whether someone has one. Instead, concussions are diagnosed based on symptoms and the results of a neurological exam. But there may be some added benefit, so even if it’s not definitive, a MIPS or WaveCel helmet—or a helmet with another system to reduce rotational impact—may be worth the extra cost.

A good fit is crucial. If the helmet is not properly positioned on the head, it might not protect you at the moment of impact. Straps must be snug and the helmet positioned correctly. Once it’s properly adjusted, only minor adjustments are likely to be necessary the next time you wear it.

Manufacturers’ styles and sizing are different, so the best way to find a helmet that fits you well is to go to a store and try a variety of brands, models, and sizes. Head sizes and shapes vary. If a helmet can’t be adjusted to stay on your head, try a different model. For kids, never buy a too-big helmet thinking the child will grow into it. 

Once you find one that fits your head the best, adjust it so that it will protect properly. Here is a three-step checklist for ensuring the right fit while in the store.

• The helmet should fit snugly but not uncomfortably, with your head partially compressing the soft foam pads inside—even before the straps are tightened.

• Select the size that fits as closely as possible without being uncomfortably tight. Then use the sizing pads, if provided, to fine-tune the fit.

• Check in the mirror to be sure the straps form a V under and slightly forward of each earlobe.

Once you have found the helmet that is right for you, use the tips from the illustration below to fine-tune the fit of your new helmet.

Our Bicycle Helmet Ratings are dedicated to Marc McEntee, a Consumer Reports testing employee for 25 years who died unexpectedly in May 2016. Marc lent his talents to many important projects during his tenure with CR, including bicycle helmets, heart rate monitors, and strollers. We honor him and his contributions.

1. The front edge should be no more than 1 inch above your eyebrows. With the straps fastened, push up firmly on the front edge of the helmet. If it moves back, the straps are too loose.

2. Push the helmet side to side and front to back: It should be snug enough that the motion wrinkles the skin at your temples.

3. A ponytail can alter your fit, so make sure to test a helmet wearing the same hairstyle you ride with.

4. To test that a buckled chinstrap is tight enough, open your mouth halfway; the helmet should press down on the top of your head as you do.

5. The front and back straps should make a V that meets just below and forward of the ear.

6. Grab the back tip and try to pull it up over the top of your head to the front. If the front of your helmet slips down, shorten the back straps.