Bike Lights: Guide to Lumens, IP Ratings & More

No matter what kind of cyclist you are, it's worth knowing what else bike lights can give you other than the ability to see or be seen. In this article, we'll delve into lumens, waterproof ratings, and more.

What are lumens?

Lumens (sometimes written as lm) are a way of measuring a light's output; in other words: how bright it is. Rear lights are usually between 5 and 100 lumens, whereas a front light can be anything from 10 up to thousands of lumens.

For comparison, the full moon on a clear night is about 1 lumen, a smartphone's backlight is around 20, and a single standard car headlight is 1200 lumens.

Cycle Lights Choose the right lights for you & your bike so you’re more visible day or night
  Well lit urban streets Well lit
urban streets
Dimly lit urban streets Dimly lit
urban streets
Unlit streets/partially lit lanes Unlit streets
partially lit lanes
Unlit country lanes Unlit country
Dark forest trails Dark
forest trails
Front lights 50 Lumens 200 Lumens 500 Lumens 800 Lumens 1200+ Lumens
Rear lights 100+ Lumens 50+ Lumens 25+ Lumens

Many lights' advertised maximum lumen output is in flashing mode, so if you're going to be using a constant mode, bear in mind that it may put out slightly less light than advertised. Where possible, we'll show max lumens for all modes on a product's page.

You may also hear about lux. Lux takes into account the surface area in which the light is spread. Several light brands have used lux previously as it's an accurate measurement for determining what we actually see in front of us. Whilst lumen is the most common measurement of light output, it doesn't always equal the light quality in a real world setting.

If you're riding on unlit roads, you're probably going to want a front light that's around 600 lumens as a minimum, but you also want to make sure that you're not going to be dazzling any oncomers. When cycling on the road, it's important to get a light that's not going to blind any oncoming traffic. To avoid this, look for a light with a narrow beam pattern.

Front bike lights

Some lights will state that they are best suited for off-road cycling, and those will be the ones that you want to avoid using on the road. That said, many of these lights will allow you to turn their brightness down, so there's no need to compromise if you're going to be riding both on and off-road. If you are going to be riding off-road at night, look for lights rated above 1,000 lumens.

It's worth knowing that light performance can drop as the battery runs out, so it's always worth having a few low-cost spare lights on you, or buying a light with a battery life that's longer than your average ride time.

If your battery is running low, switch to a flashing or eco mode where possible. Don't risk using a flashing mode on unlit roads, but in built-up areas it's ideal and can help to make you even more visible.

Mounts and brackets

No matter where you're riding, the strength of your light's mount is pretty important. Some mounts can slip if you're riding over bumps, and attempting to adjust them whilst riding isn't easy (and nor do we recommend it!). Because of this, we'll always try to give an indication of how secure the mount is.

Many rear lights are secured to your bike with a simple silicone strap, making them easy to attach and remove. Safety lights will also be secured this way.

Many front lights also feature straps, but you'll also come across clamp mounts. These are a lot more rugged and are able to withstand bumpy trails with ease. They'll usually require tools to assemble so they aren't as quick to secure to your bike as a strap mount, but will often feature a quick release for easy removal. It's worth considering a light with a silicone strap mount if you're going to be swapping your light between bikes.

Waterproof rating

Riding in the UK and Ireland means you're definitely going to need a set of bike lights with a decent waterproof rating. Waterproof ratings on lights vary, so it's worth knowing what those letters and numbers mean.

Waterproof ratings begin with 'IP', which stands for Ingress Protection. It will then be followed by two numbers - the first number is the protection from solid particles (dust), whereas the second number is the protection from liquid.

We don't recommend buying a light that's less than IP64. A light rated at IP63 will allow water spray in at a certain angle, whereas a light rated at IP64 is protected against spray from any direction. As you continue up the scale, the waterproof protection is even greater: IP67 can withstand immersion up to 1 metre, which should be more than enough for any cyclists' needs!

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