How To Calculate Litre Capacity of a Bag? How Big is Your Backpack? - Reviews (2022)

Whether you are a frequent traveller or an adventurist, one of the essential companions you need to carry with you is the Rucksack bag. When it comes to a backpack or rucksack bag, it should be able to handle everything you would need for surviving for the period that you would be on the move.

From that perspective, it is essential to understand how much capacity does your new bag offer, or rather how to calculate litre capacity of a bag. Let us check out the options you can use to measure the capacity of a rucksack bag. In addition, we will also check out a few specific sizes of the bags and learn how they fulfil your needs.


  • 1 How to Calculate litre capacity of a bag?
  • 2 How big is a 20 litre backpack?
  • 3 How big is a 25 litre backpack?
  • 4 How big is a 30 litre backpack?
  • 5 How big is a 40 litre backpack?
  • 6 50 vs 65-litre backpack – How to Choose?
  • 7 65 vs 75-litre backpack
  • 8 Which Backpack is Right for me?
  • 9 The Parting Thoughts on Litre Capacity of a Backpack

How to Calculate litre capacity of a bag?

Well, ideally you will find it described on the bag. However, if you are unsure of the volume capacity of your bag or just looking to confirm the claims of the manufacturer, there are a few options and methods you can use to calculate litre capacity of a bag.

One of the common methods used is to use small Ping-Pong balls or dried beans to find the volume of your bag. Prepare a few balls or collect enough dried beans and begin the exercise.

  • Take a measuring cup and begin filling your bag with the beans or balls.
  • Once the bag is full, you are aware of the number of the cups you needed to fill the bag to its full capacity.
  • Based on the measuring cup size and the number of cups used, you can easily arrive at the litre capacity of your bag.
(Video) How Backpack Liters Are Calculated: Explained!

For instance, if the measuring cup is of 500 ml capacity and you have used 40 cups, the total capacity of the bag is 20 litres. While you may fill the main compartment alone or fill out the outer pockets as well.

How big is a 20 litre backpack?

The 20-litre backpack capacity should be ideal for daily travels. In case your travel begins in the morning and ends by night, it should be an ideal option for your needs. The size is quite limiting, and you will need to go through a lot of compromises, but being precise, how big is a 20-litre backpack?

A 20-litre bag should meet the following needs:

  • The bag is ideal for a day’s travel, definitely not more than that.
  • Filled to the fullest capacity, it should ideally have a weight of around 7 to 9 kgs depending on the material used.
  • The weight of the empty bag measures around 800 to 900 grams.
  • The bag should ideally take a load of a good sleeping mat, a pair of trousers, a bottle, along with a jacket and a pillow.

How big is a 25 litre backpack?

A 25-litre backpack is ideally a good option for you – once again a daily trip. If your needs are slightly more than what we have outlined above, a 25-litre bag can be a good option. In a way, there should not be a huge difference between a 20 litre and 25-litre bag.

But how big is a 25-litre backpack? The 25L backpack should ideally meet the below needs:

  • Best suited for a day’s travel. The maximum it can take is an overnight stay.
  • The bag should pack an additional pair of clothes than what we specified above. The bag should be able to host your laptop as well.
  • The full filled bag should weigh around 10 kg.
  • The empty bag weighs around 900 grams to a kg.
(Video) Ultimate Backpack Size Guide - What Size Backpack Do I Need for School, Work, or Commuting?

How big is a 30 litre backpack?

The 30-litre bag can be a perfect match for those looking for the weekend trips that may take around three days max. It will let you carry sufficient options for survival through a couple of days.

But how big is a 30-litre backpack? Ideally, you could expect the below from a 30-litre Rucksack bag:

  • In addition to your daily wear, water bottles, and other items we already covered above, the bag should let you carry a sleeping bag as well. You should be able to carry spare clothing, water, food, and other essential items.
  • The empty bag should weight anywhere between 600 grams to 1000 grams depending on the material and design.
  • Filled to full capacity, it should weigh around 12 to 13 kgs.
  • The bag is best suited for use on the weekend trips. You may need to make a choice between sleeping bags and other essentials.

How big is a 40 litre backpack?

The 40-litre backpack comes under the medium rucksack bags. It should be your ideal companion for overnight camps, hiking and similar other requirements. They can carry heavier loads than the day packs we just discussed.

Again, but how big is a 40-litre backpack? A few features that these 40L bags come with include:

  • The bag should weigh around 1 kg to 1200 grams when empty.
  • The fully filled weight of the bag will range between 12 to 15 kgs.
  • The bags come with all the features on a 30-litre bag but will pack in extra options for additional padding and storage. Camping gear or sleeping bags or a couple of additional utensils should ideally be accommodated.
  • The 40 litre backpack is an excellent option for overnight camps and other high demand needs.

50 vs 65-litre backpack – How to Choose?

Are you confused between a 50 litre vs 65-litre backpack? Well, it should be dependent upon what you tend to carry. A 50-litre bag should ideally weigh at 13 to 15 kg, while the 65 kg bag should weigh around 18 to 20 Kgs.

(Video) Guide to Backpack Sizing - Volume & Liters

Carrying weight worth 20 kgs may not be an ideal condition. Of course, when you have a larger bag, you tend to be tempted to carry more. We would want to stick with a capacity of around 50 kgs as such, and we believe it can help you carry enough of the needs. Of course, if you are with a family, you will need more items to carry and be forced to opt for a larger bag. Even then we would advise opting for a 50 kg bag itself, or better still two bags with 50 kg and 20 kg so that you can share the weight between your family members.

65 vs 75-litre backpack

This is yet another confusion that frequent travellers tend to face quite regularly. We would indeed not recommend opting for a bag with a high capacity as 75 litres. Of course, a bigger bag is tempting, and you would feel like carrying your entire wardrobe! But is it really needed?

What is most important is the personal packing style. Keep yourself confined to the exact requirements. With high capacity bags like 75 litres, you may tend to break your back. Moreover, with that kind of a load on your back, you would not be able to enjoy your trip either.

Which Backpack is Right for me?

Now that we have understoodhow to calculate litre capacity of a bag, how big is a 30-litre backpack, 40-litre backpack etc… now let’s see which is the right backpack for you. Here is a small infographic which shall help you to understand which backpack size should be the best pick for you.

How To Calculate Litre Capacity of a Bag? How Big is Your Backpack? - Reviews (1)

The Parting Thoughts on Litre Capacity of a Backpack

With the above, you should now be familiar how big is a 25/30 etc… litre backpack and how to calculate litre capacity of a bag. The crux of the matter is to learn to pack your bags with a proper focus on the right things that you will be using in your trip.

Please share your thought below on how much can you fill-in in your backpacks, in the comment section below.

(Video) Calculating The Volume Of A Backpack In Liters

How To Calculate Litre Capacity of a Bag? How Big is Your Backpack? - Reviews (2)

Sandhya Sinha

A mom to 2 kids, Sandhya has been passionate about cooking and home decor since her early twenties.She loves spends more than enough time researching & then buying useful home & kitchen appliances and trying out new recipes.

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(Video) Which Bag Size Do I need? BAG GUIDE


How do you calculate the Litre capacity of a bag? ›

The first thing you need to do is multiply the length by the width by the height. That gives the number of cubic millimetres. To calculate the number of litres, you then divide that number by a million.

How do you calculate backpack capacity? ›

You can get the accurate volume of the backpack by checking the amount of balls/beans you have filled in. For example, if you are using a 1L measuring cup, and the backpack can take 20 cups of ball/beans, then the volume of the backpack is simply 20L.

Is 23 Litre backpack big enough? ›

Medium: 21 to 30 liters

A school backpack of 21 to 30 liters is suitable for this. This is the most common size for backpacks. The bags have enough space, but are not larger than necessary.

Why are backpacks measured in liters? ›

Because the characteristic of a backpack in question is volume or how much content it can hold, not mass. An extreme example: If I fill lead into a 20l pack, I get ~225kg, if I fill styropor into a 50l pack, I get about 2.5kg. Mass is still specified sometimes to give the empty mass of a pack.

How do you measure litres capacity? ›

1 litre = 1000 millilitres. If capacity of a bucket is 10 litres it is written as 10 l. If capacity of a small bottle is 100 millilitres it is written as 100 ml. The milkman measures milk in liters.

How do you calculate capacity? ›

The formula for calculating capacity of an Individual Resource:
  1. Individual capacity per day = sum of (working hours per day - team availability per day)
  2. If a resource is assigned to a team 100%, their individual capacity is synonymous with team capacity.

Is a 45 Litre backpack big enough? ›

Yes, 45 liters is more space than most people will need in a day hiking pack. The sweet spot for day packs is more like 15 – 30 liters, which is enough space for a day's worth of food and water, warm layers or rain gear, safety essentials, and other small items.

Is 27 liters a big backpack? ›

24-26 liters is considered a medium-size backpack and is probably the most popular bag capacity out there. It's great for taking to school or work, depending on the styling, and can also be a great travel pack for taking on a plane. Here is a potential packing list for that size depending on where you're headed.

How do you measure a bag size? ›

To measure your bag, place it upright with the wheels (if it has them) on the bottom and the extension handle on top, but don't extend it. Measure from the bottom of the wheels up to the tallest part, which is likely to be the handle.

How many litres is a 10kg bag? ›

The suitcases have capacities of about 25 to 50 liters, which equals about 10kg of luggage.

How many kg is 40l bag? ›

Different strokes, etc. The bag I take as checked luggage is 40 litres. Typically weighs 11-13kg fully packed.

How many litres is 30 kg of luggage? ›

The suitcase weights 3kg, so that means I can take 20kg in 90 liters, 4,5 liters per kilo. As in my next trip I wanted to take 30kg (including suitcase), that means 26kg x 4,5 = 117, the suitcase I found was a Desley that weights 4.2kg. So filling this 117 liters with the usual stuff, will give me exactly 30kg.

How much can a 70L bag hold? ›

You can expect to fit the following in a 60-70L backpack: Water bottles. A heavier jacket and extra sets of clothing. A larger first aid kit.


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