Will a Bike Helmet Rain Cover Fit Your Helmet? Our 52-63 cm Fit Test

A bike helmet rain cover only does its job if it fits. Too loose and it flaps, lets water in and can work its way off. Too tight and it won't go over your helmet at all. Some riders have told us they found a cover too big or couldn't get it snug, so we put one of our waterproof hi vis helmet covers on two real helmets and filmed what actually happens.

The video's just over a minute long. It's the quickest way to see whether the cover will suit the helmet you already own.

The short answer: the cover fits helmets sized about 52 to 63 cm, which is the size printed inside your helmet. That takes in most adult helmets and youth helmets, visors included. A stretchy cord round the hem pulls it snug under the rim.

What the fit test shows

Everything in the video is our own footage: one cover, two helmets we use at home, no special helmet picked to flatter it. If you want to skip to a part, here's where each bit starts:

• 0:00 adult helmet with a visor (58-61 cm)
• 0:11 pulling the stretchy cord
• 0:23 youth helmet (52-58 cm)
• 0:35 snug from every angle
• 0:45 room to spare, up to 63 cm

Adult helmet with a visor, 58-61 cm

The first helmet is an adult city and MTB style helmet, size 58-61 cm, with a visor at the front. The cover pulls straight on from front to back and goes right over the visor. You don't have to take the visor off, and the hem ends up underneath it.

Pull the cord and it tightens under the rim

The cover closes with an elastic cord threaded round the hem, locked by a spring toggle. Pull the cord, let the toggle grip and the hem gathers in under the helmet's rim all the way round.

This is the bit that matters. The cord is what turns a loose cover into a snug one, and it's why the same cover can fit a big adult helmet and a much smaller youth one. With the adult helmet turned round you can see the finished fit, with the reflective stripes lying flat along the sides.

Youth helmet, 52-58 cm

Next is a youth helmet, size 52-58 cm, the one our 13 year old rides in. It's noticeably smaller, with a short visor and a built in rear light. The same cover goes on, the cord gets another pull and the hem gathers in to fit.

Turned all the way round, it's snug from every angle. You'll spot some spare fabric gathered at the back. That's normal at this size, and it's also why we don't claim the cover fits anything smaller than 52 cm. With hands off, the cover sits firmly in place on the helmet.

Room to spare, up to 63 cm

The biggest helmet in the video is labelled 58-61 cm. At the end we go back to it with the cord drawn, and there's still give in both the fabric and the cord. That spare room is why we list the fit as up to about 63 cm. It's worth knowing because plenty of large and XL helmets are labelled 58-62 or 59-63 cm.

How to check your helmet size

You probably don't need a tape measure. Look inside your helmet: cycle helmets made to the EN 1078 standard carry a label or sticker with their size range in centimetres, something like "M 54-58 cm". If your helmet's range sits anywhere between 52 and 63 cm, it's within the range our cover fits.

Label worn off? Measure your head instead. Run a soft tape round the widest part, about 2.5 cm above your eyebrows and just over the tops of your ears. Your helmet's size range will include that number.

Brands size helmets differently, so one maker's medium isn't always another's. As a rough guide, lots of UK and European brands sell a medium or youth helmet at 52-58 cm and a large at 58-61 cm, the two sizes in our video. Some large and XL models go up to 62 or 63 cm, which is still in range.

How to fit a bike helmet rain cover properly

It takes less than a minute once you've done it a couple of times:

1. Hook the front of the cover over the visor or the front edge of the helmet.
2. Stretch it back over the shell until the hem sits below the rim all the way round.
3. Check it's straight, with the reflective stripes even on both sides.
4. Squeeze the toggle, pull the cord until the hem gathers in under the rim, then let go of the toggle so it locks.
5. Tuck the loose end of the cord inside the hem so it doesn't flap about.

Have a practice at home first. Fitting a cycling helmet rain cover for the first time at the side of the road, in a downpour, with cold fingers, is nobody's idea of fun.

What it fits, and what it doesn't

• Adult helmets: commuter, city and MTB helmets sized roughly 52-63 cm
• Helmets with a visor or peak: the cover goes over the top and the hem closes underneath
• Youth helmets: 52-58 cm youth helmets fit, as the video shows
• Small children's helmets: we haven't tested anything under 52 cm, and the cover is usually too big for smaller children's helmets
• Built in rear lights: the cover goes over the whole helmet, so it covers an integrated rear light too

On that last point, every cover has a small loop on the back where you can clip a rear light, so you're not left without one. And one more honest note: we haven't yet tried the cover on a long, pointed road or aero helmet. If that's what you ride, check the size label and drop us a message if you're unsure.

Because the same cover fits both an adult helmet and a teenager's, the helmet cover 2 pack is an easy way to sort out two riders in one household. You can see every colour in our helmet covers collection.

Why a snug fit matters in UK rain

The UK averages around 159 days a year with at least 1 mm of rain, based on Met Office figures for 1991-2020. On a bike that rain comes at you from the front and the side, not just from above. A bicycle helmet rain cover that's pulled snug keeps water out of the vents and stays put instead of flapping. It also keeps the hi vis fabric and reflective stripes facing out, where drivers can see them.

If you're working out what else to wear on wet rides, our guide to cycling in the rain covers clothing, kit and riding tips. Still deciding whether you need a cover at all? Do cycling helmet covers actually work? goes through the pros and the downsides. And if you're comparing covers, how to choose the right cycling helmet cover explains what to look for.

Frequently asked questions

Will a bike helmet rain cover fit my child's helmet?

Ours fits youth helmets sized 52-58 cm, like the one in the video, which is a common size for older children and teenagers. We haven't tested it on children's helmets under 52 cm and it's usually too big for them. Check the size label inside the helmet before you buy.

Does the cover go over a helmet visor?

Yes. It stretches over the visor or peak, and when you pull the cord the hem closes underneath it. You don't need to remove the visor first.

How does the cover stay on?

An elastic cord runs round the hem and locks with a spring toggle. Pull it tight and the hem gathers in under the helmet's rim all the way round, and that's what holds the cover in place.

My helmet has a built in rear light. Will the cover block it?

Yes, an integrated rear light will be covered, because the cover goes over the whole helmet. Each cover has a small loop on the back so you can clip on a separate rear light instead.

How do I find out what size my helmet is?

Look for the label inside the shell, which gives a size range in centimetres. If it falls anywhere between 52 and 63 cm, the cover is in range. No label? Measure round your head about 2.5 cm above your eyebrows.