20L backpacks are great for short walks such as a few hours as you will easily be able to fit your water, some snacks and another layer with ease. If you are hiking for the full day then opt for a 30L. You will be able to bring several litres of water, lunch and your waterproofs and still have space for the rest of the essentials.
Ultimately what bag you want to bring all depends upon what is most comfortable for you. That usually is the smallest size that fits everything in but some backpacks feel better than others. Larger technical bags with padded straps and hip belt may feel better on the trail than a smaller backpack which digs in under the weight.
One of the many good aspects of hiking is that you can usually grab whatever you already have and use that to get started. So long as it fits all you need in it then it’s good to go, but in case you are thinking about investing in a new backpack, maybe even a technical one then ill give you a hand!
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20L vs 30L Backpack For Hiking
Below is a table summerary of when you would use each bag.
| Considerations | 20L Backpack | 30L Backpack |
| Hike Duration | Half Day Hikes | Full Day Hikes To Multi-Day Hikes If Packed Light |
| Layers | Waterproof jacket, Fleece Or Windbreak | Waterproof Jacket, Waterproof Trousers And Fleeces |
| Extra Gear | Only Essentials | All Essentails Plus Small Camera, Cooking Gear And Extra Layers Or Hobby Equipment |
| Water | 1 Large Bottle (1L) Or 2 Small Bottles Or Hydration Bladder If Compatible (1-2L) | 2 Water Bottles And Hydration Bladder (2+L) |
| Weather Conditions | Predictable, Mild And Dry | Can Cope With Wide Range Of Conditions |
| Remoteness | Local Walks Close To Villages Or Towns | Day Or Overnight Level Of Remote (Enough Equipment For Emergencies And Supplies). |
| Emergency Preparation | Small First Aid Kit And Survival Bag | Larger First Aid Kit, Survival Bag Or Bivy. Could even take a tent for camping |
| Food | Snacks, Lunch | Snacks, Lunch, Additional Meals |
| Weight | Lightweight Backpack Bare Essentials | Heavier Backpack, Tendency To Overpack |
| Technical Capability | Small hip belt If Any, Less Padding On Shoulders, Fewer Technical Features | Hip Belt With Pockets, More Padding, Structured For Optimal Weight Distribute, Improved Breathability, More technical Features. |
The best rule to follow for backpacking is to make it fit COMFORTABLY in the smallest backpack possible. In order to work that out you need to work out exactly what you need to take on each trip. Luckily for most the basic kit list is pretty straight forward so you know what set size yours will be. You then only need to adjust for duration, weather conditions and any technical equipment such as crampons you need to bring and of course can you fit your camera!
As you can see above the 30L backpack has loads more room and I didn’t even put anything in the additional pockets but everything did fit into the 20L backpack even if it looks full. With the use of dry bags you could compress your fleece and waterproofs which would create more space if you needed to fit more into it.
Essential Hiking Kit list
The hiking essentials should be packed into your backpack for every hiking trip you do and are as follows:
- Waterproof Jacket
- Waterproof Trousers
- Water
- Food
- First Aid Kit
- Warm Layer e.g. Fleece
- Sunglasses- summer and winter
- Suncream
- Map
- Compass
- Shelter- survival bag if not camping
- Multitool
- Head-torch
- Power bank (or turn your phone off or airplane mode).
The basic hiking principles when walking around your local park are pretty simple. You look outside, see what the weather is like and pop on the layers you think you need and grab a bottle of water. If you misjudge it you just hide from the rain in a local cafe or head on home.
For those longer hikes in more remote places you are packing to be prepared as you simply cannot bail. A full waterproof set may seem overkill until your sunny morning turns into a torrential downpour by afternoon. Even if it’s cloudy you can still get sunburn and always bring sunglasses even in winter. There is nothing worse than spending the day squinting. It can be bright even with cloud cover and the glare can be intense if you are near water or snow.
I am notoriously bad for forgetting my multitool and most of the time I don’t feel like I need it but it is one of those items that come in surprisingly useful and never in the ways you predict.
If you are planning on camping then a multitool or a penknife will come in super handy. The same with the head torch. Unless you are planning to watch the stars then you would never think to bring one and mostly wont use it. It is there for emergencies. On more remote hikes getting lost is a possibility, or misjudging terrain can add hours onto a hike. Last thing you want is to be cutting it fine with the daylight and worse case scenario they are excellent to signal for help without draining your phone battery.
After you grab these items you then need to adjust quantities for each hike you plan to take and this can take some getting used to and trail and error.
How Do You Know How Much Water To Take On A Hike
To estimate how much water you need to take on a hike you need to consider duration, terrain, elevation changes and weather conditions. For most people taking 2L of water will be sufficient on a moderate full day hike in mild conditions.
In hot conditions you can easily double to 4L plus. For example, my 1.5L hydration bladder only lasted me 2 hours during a hike near Seville in 35 degrees C. I planned for this and also took another 1L bottle with me to make sure I stayed hydrated.
You will also need more water if you are climbing prolonged uphills as you will be working hard and therefore sweating more. Higher altitudes also dehydrate you faster because of the thinner, drier air. In conditions like those you will need more water even if it’s cold.
If you are worried you need to carry litres and litres of heavy water then there is another solution which is frequently used by thru-hikers. You can buy water filters and water purification tablets so that you can then refill your bottles any time you pass a suitable water source such as a stream. This is also a good back up in case you under estimated the conditions or the time out hiking.
How Do You Know How Much Food To Take Hiking
In order to work out how much food to take hiking you need to start with what you would normally eat in a day and cross reference it to how long you expect to be out on the trail for. Then you can create bigger portion sizes for the meals and carry more snacks to compensation for the increased energy expenditure of hiking.
Below is an example table of what and when to eat when hiking.
| Time | Food |
| 0800 | Eaten prior to hike. If you hike before breakfast then bring it with you e.g. sunrise hikes. |
| 0900 | |
| 1000 | Mid morning snack- choose something with slow release carbs so you don’t have that sugar crash! Consider snack cheese or a fruit and nut mix. |
| 1100 | |
| 1200 | Pack Lunch- consider bringing a jet boil for something warm. Do not be surprised if you want to eat lunch earlier than you are used to. Hiking needs fuel! |
| 1300 | |
| 1400 | Snack #2 |
| 1500 | |
| 1600 | Snack #3- choose something that is a real pick me up to keep you going for the final push to the finish. Sweets are a good moral boost. |
| 1700 | |
| 1800 | Dinner- eaten at home |
As you can see you likley only need to bring a packed lunch and at least 3 snacks for a day hike. You will be expending more energy than normal so don’t skimp on the snacks. They are the perfect little boost to get your through the tough bits. I would always bring a few more snacks just in case there’s an issue and I spend longer out than I planned. An emergency 24 hours of food can be useful if you are planning to camp or go really remote in case you are waiting a long time for help should you need it.
If you start your hike before breakfast to catch the sunrise or simply can’t eat breakfast as soon as you get up then you need to take someone on the trail. Consider flapjacks or making yourself a bagel or breakfast wrap with some fruit. If you have a camping stove with you then instant porridge will be a good option. You can even get breakfast options from outdoors shops that include sausages and beans.
The process continues to be simple for multi-day hikes or camping. Work out what you normally eat in a day. Plan around the meals, then how many snacks you normally eat during the day. Then add a few more snacks to each day because hiking will make you hungry and depending on how long and remote some spare food in case of emergency.
Can You Camp With A 30L Backpack?
You can camp with a 30L backpack but it will require compressible equipment alongside simply packing just the bare essentials. You will be adding the above hiking list with tent, sleeping mat and sleeping bag and you will need to consider more food and water.
Many 30L hiking backpacks have additional straps to attach your sleeping mat, otherwise it is something that can be put under your top flap with a bit of weather protection. This is especially true for the roll mats or foldable ones. These are also fairly cheap and ultralight. If you have a inflatable sleeping pad for a bit more comfort then how small that can compress will be the leading factor.
As for your sleeping bag, those made of duck or goose down will be the most compressible maximising space in your backpack. Some of the summer sleeping bags pack down to less than the size of a 1L bottle of water.
Finally the bulkiest part which is your tent or shelter for the night. If you are happy just sleeping under a bivvie, tarp or single walled tent then you will maximise your space and save on weight. Many of these are held up by using what is around you and your hiking poles.
If you’re joining a campsite or just simply prefer the warmth and privacy of a traditional tent layout then choose one that is small as your needs and packable. The fabric is usually fairly compressible and then place the poles in seperately. If you are in a group with a larger tent split up the parts to maximise space.
If you’re camping then you will need to bring a camping stove. I have a Jetboil (Amazon) and its excellent design means everything fits perfectly together minimising the space it takes to carry it. Then of course any meals you need to bring and even more snacks. Also consider thermals, hats, gloves and a warmer jacket as the night closes in alongside your spare dry clothes for the evening.
People can and do go backpacking and camping with a 30L backpack but you will not have much room for luxuries. You will be wearing the same clothes each day with a change of socks and underwear. You will be relying on filtering water or your campsite for supplies but it is totally doable.
The longest so far I have lived out of my favourite 30L bag (which I take everywhere I can) is 10 days. You just get used to having 1 spare outfit and washing your underwear in a sink. You can buy fabric wash leaves in a handy travel pot such as Lifeventure fabric wash leaves (Go Outdoors) or you can make your own by cutting down laundry sheets and putting them in a small tin.
Conclusion
Whether to bring a 20L or 30L backpack all depends on the type of hike you are doing. For day trip out hiking you can easily use a 20L backpack and carry everything you need and taking a 30L backpack will probably be overkill.
However, if you’re venturing far away from the classic pub walks then I would consider the 30L backpack because you can take more supplies and they often have better weight distribution features to make it more comfortable such as space for hydration bladders and padded hip belts.
