Why Are Backpacks Measured In Litres (Helpful Guide)

In the backpack, the gears can be of different sizes and volumes can describe the capacity easily. The measured volume is always taken in litres because of the standards set by the authorities and manufacturers. This is the reason why backpacks are measured in litres.

There are more points that you should know about measuring the backpack.

So, keep reading.

What Are The Methods Of Measuring a Backpack?

There are different ways of measuring the backpack, i.e., measuring the volume of the backpack and measuring the actual dimension of the backpack.

Both methods are quite different from each other and this is why we are going to discuss them in detail one by one.

#1. Water-filling Method (Measuring the Volume)

No matter, which type of backpack you are looking for or currently carrying with you whether it is a school backpack, hiking backpack, or travel backpack with trolley sleeves.

You must have seen 40 litre, 30 litre or 20 litre in the description/specification section of the backpack when you are purchasing it.

This is what represents the volume of the backpack and also the storage capacity of the whole backpack.

The volume of the backpack is a total three-dimensional space that can be filled in a backpack.

Why Are Backpacks Measured In Litres

To measure it, the manufacturers fill the whole backpack with water because the water can take any space and size and this is why you get the idea of the whole volume of the backpack.

This means that the whole volume required to fill the water must be equal to the volume of the backpack.

Sometimes, the volume is measured separately for each compartment to get a better idea of the capacity of the compartments.

Then, the manufacturers of the backpack sum up the volume of each compartment inducing the external pockets and side pockets to get an overall volume of the backpack (which is more accurate).

If you are measuring the volume of the backpack at your home, then you should only measure the whole of the main compartment by filling them with water. 

There is one more way that you can use to calculate the volume which is using the dimension. So, let discuss it.

#2. Dimensional Method (Measuring The Dimensions)

Measuring the Dimensions of the backpack is the easiest way to get an overview of the backpack’s capacity.

You will need a ruler or a measuring tape for it and after finding the perfect measuring tool for yourself you need to measure the exterior dimensions, which are length, height, and weight.

The first step is to measure the external dimensions of the backpack using the measuring tape. 

If you want to go one step farther, then you should measure the interior dimensions which will give you an idea about what you can keep in your backpack.

Once, you have the dimension (in centimeters) you can multiply them and divide them by 1000, to get the volume of the backpack in liters.

Also, the dimensional method is used to measure the size of the backpack.

However, this method will not give you the exact volume of the backpack, you will just get a rough idea about it.

Why backpacks are measure in liters?

The backpacks are measured in liters but sometimes ounces too. This is because every measurement can not be universally acceptable, this is why to overcome this problem the backpacks are measured in liter which represents the volume of the backpack. 

Also, the cubic centimeter is not a standard unit of measuring volume, this is why the volume is converted into liters after you measured the volume using the dimensional method.

To determine the capacity of the backpack, the manufacturers use a basic formula that is directly proportional to the length, width, and height of the backpack.

In this formula, the dimensions of the backpack are measured and then they are multiplied together and divided by thousands.

The formula can be written as – Length*Width*Depth(in centimeter)/1000.

Backpack Dimensions Explained:

The backpacks come in different sizes and different capacities, each size of the backpack is designed for specific use.

For example, a 40 to 50 litre/liter backpack is generally used for hiking while a 20-liter backpack can be good for light packing and short trips.

Volume/CapacityDimensions (inches)
8 Liter Backpack17*8*5  inches
20 Liter Backpack17*11*9 inches
30 Liter Backpack21*13.5*9 inches
40 Liter Backpack21*14*9 inches
50 Liter Backpack29*13*10 inches
70 Liter Backpack30*18.5*13 inches

How To Measure A Backpack at home?

Although, the backpack size and the dimension are already specified by the manufacturers and the seller on their website and sometimes in stores too.

But, if you want to confirm it yourself. Then you need to follow two simple steps.

#1. Meaure the Dimensions of The Backpack

First, get a measuring tape or ruler to measure the dimension of the backpack.

You should start by measuring the dimension of the backpack and divide it by 1000 to convert volume into liters.

You can also measure the internal dimensions of your backpack to get a more accurate measurement of the backpacks.

#2. Measure Each Compartement Separately

Measuring each compartment separately can be a tough job and this is why most manufacturers do not do it.

So, the volume that you see in the description of the backpack is precise volume.

You can measure each compartment separately and then sum them together to find the final and total volume of the backpack.

So, this is how you can measure a backpack at home.

In conclusion, the backpacks are measured in liters to maintain the standard of measuring the volume of the backpack. This is an effective approach because the volume can be easily measured in liters using the water filling method rather than inches or cubic centimeters.

Frequently Asked Question:

What Are The Dimensions Of A Backpack?

The dimensions of the backpack simply mean the length, height, and width of the backpack. The dimension can help you to know what size of items you can fit into your backpack.

How Big Is a Standard Backpack?

32 Liter is a standard backpack size of the backpack which has a dimension of about 19.57 x 15.31 x 3.9 inches. This backpack can be travel backpacks, school backpacks, work or office backpacks.

Is 65l Backpack Too Big?

65 liter backpacks are big for schools and travel trips but in case you are hiking then this can be a good option as you can carry a lot of stuff. Also, it will let you attach the tent and sleeping bag if you want.