Waterproof roll top cycling backpack - what size is right for you?

Size does matter, especially when it comes to choosing the right size waterproof roll top cycling backpack. Choosing the right size for you can seem complicated, as the standard unit of measurements is volume, to display this, most companies will proudly tell you how many litres their backpack holds. Of course, it is good to have a standard unit of measurement, and volume is the logical method when considering how much you can fit into a bag. But in the real world, no one is going to be filling their bag with water! The best waterproof backpacks for cycling are designed to prevent water from getting in.

You need a waterproof backpack for cycling that will hold everything you need while keeping your belongings safe and dry. Realistically you do not need an enormous backpack, such as the ones you see being lumbered around by backpacking travellers. It is simply not practical or comfortable to cycle with an overly large backpack. Equally, you want to make sure that your backpack is large enough to hold everything you need. 

How many litres do you need to carry?

Here is a quick breakdown of backpack sizes:

10L to 15L - Hydration packs and bare essentials

Small and compact. Perfect for a hydration pack and carrying the bare essentials, such as puncture repair kit and some light snacks.

16L to 20L - Perfect for cycling day trips

You will be able to carry everything you need for a bicycle day trip. However, you will struggle to fit a laptop, change of clothes or everything you would want to carry if you are planning to commute by bike. 

21L - 25L - Perfect for lightweight cycling commuter

If you are cycling to work and can store some of your clothes, shoes or toiletries at the office, this size bag could be enough to carry what you need when commuting by bike. They are generally lighter and if you are not looking for your backpack to double up as an overnight or weekend bag, you may prefer this more compact size. People with more slender bodies will find these lighter backpacks more comfortable and easier to carry. 

26L to 30L - Full-time cycling commuter and weekend bag

The perfect size backpack to carry everything you could need from a cycling backpack, without being too cumbersome. At the higher end, a bag with a 30L capacity will have enough space to carry your laptop, change of clothes and just about anything else you could need throughout the day or night. Making this an excellent sized backpack for cycling commuters. 

Even if you plan on working out in the gym at lunch, a 30L backpack is big enough to carry multiple sets of clothes and keep your dirty clothes separate (if you get one with dedicated compartments). These bags have enough capacity to double up as a weekend bag. With enough space to carry all you will need for a weekend away. Carrying everything on your back for a short trip is a lot more comfortable than a holdall or mini suitcase, especially if you are using public transport. 

30L + - not practical for cyclists

Extra large. Not practical or comfortable for cycling. Anything over 30L will start to impair your visibility when checking over your shoulder for passing motorists. If you are looking to embark on a cycling tour, invest in panniers or frame bags to carry your extra equipment as opposed to having such a heavy load on your back. 


When looking at the dimensions for your next waterproof backpack for cycling, consider what the largest item is likely to be that you will need to fit in there. For most cyclists, it will be a laptop. Therefore look for a backpack that has a padded laptop compartment, a 15” laptop with an average height of 20cm and width of 34cm will comfortably fit in a 30L backpack. 

Even if you are not looking for a backpack to carry a laptop, smaller packs fill up surprisingly quickly. 

Right Size and fit for cyclists

Although technically any backpack will serve the purpose of carrying your belongings on your back while cycling. If you are looking to commute on your bicycle or use your backpack regularly to carry everything you need on longer rides, it is worth investing in a waterproof backpack for cycling.

Cycling backpacks are designed with cyclists in mind. While on the bike, your body is not in the normal upright position that you are when walking. To combat the more horizontal position on your back, you should look for a backpack that comes with a hip belt. Additional straps on the hips and chest not only takes some of the strain from your shoulders by balancing out the weight. They also keep your backpack in place and prevent your it from rolling off your back altogether. 

Also, as a cyclist, you can expect to sweat while out on the bike, no matter how hard or easy you are taking it, we all want to try to avoid sweaty back syndrome. A backpack designed with cyclists in mind will feature breathable padding on the back, to help prevent a build-up of sweat on your back. This padding typically has channels allowing air to flow through and cool your back, while also reducing the surface area that is making contact with your back. 

Finally, some additional features that you will benefit from by getting a waterproof backpack for cycling are improved waterproofing, extra easy-access pockets and a clip or loop to carry your helmet or bike light. 


Check the dimensions and measure the largest item that you will need to carry within your backpack, often a laptop, to make sure it is large enough. Anything between 20L - 30L capacity is perfect for a waterproof backpack for cycling. Any less and you will be frustrated by the lack of space and functionality. A 30L backpack can easily accommodate a laptop, spare set of clothes (or two), towel, shoes, toiletries and double up as an overnight bag. Any more than 30L and you need to be questioning what you are taking on your commute or bike ride.