How to Easily Measure the Volume of Your Backpack in Liters 

 September 30, 2023

By  Keith Terrell

Have you ever tried to pack a week's worth of hiking essentials into your backpack, only to find out it's just not large enough? Perhaps you've racked your brain trying to figure out why your friend's backpack is the same size as yours, but he’s mysteriously been able to fit in two extra sweaters and a sleeping bag in it! The secret lies not in his packing skills but merely in the volume of his backpack. Think about it like this: Two houses can look similar from the outside, but one can have an attic that dramatically increases the interior space. The same principle applies to backpacks. 

To estimate the volume of your backpack in liters, measure the height, width, and depth of the main compartment of your backpack. Then multiply these three values together. Note that this method only gives an approximate result and does not take into account external pockets or material properties. 

Knowing how to measure the volume of your backpack in liters will take your packing skills to a new level and ensure you never suffer from a lack of space on your adventures again! So get ready for us to dive into the world behind the zippers and buckles and free you from unnecessary packing stress for good!

Measuring Backpack Volume in Liters

Backpacks have become indispensable for many people, from students to hikers to professionals. Choosing the right backpack size helps ensure that you can carry everything you need without straining your back or shoulders. The universal unit of measurement for the volume of a backpack is the liter (L), but measuring it can be challenging. To determine the right backpack size you need, you need to know how to measure its volume correctly.

Suppose you want to buy a new backpack with a certain capacity. You go online and find two different backpacks, both of which are supposed to have a capacity of 30 liters. However, when you receive the backpacks, one feels much bigger than the other. The reason for this is that there is no standardized method for calculating the volume of backpacks from different manufacturers. It is also because backpacks have different shapes with rounded edges, multiple pockets, and compartments, which makes measuring their volume complicated.

To determine the capacity of a backpack more precisely, some users use water as a measuring tool. They fill their closed backpack with water and then pour the liquid into a bucket to determine the capacity of the backpack. However, this only works if the backpack they are measuring has no holes or leaks.

Another efficient method is to accurately measure the outer dimensions of the backpack. Measure each level of the backpack's surface from top to bottom and side to side while it is empty and standing on a flat surface. Be sure to measure each individual compartment that makes up the backpack from edge to edge.

Some argue that the sole use of these linear dimensions in the correct calculation of volume can include unusable spaces, especially for smaller bags with curved edges or complex compartments. Others, however, argue that the linear dimensions are still essential for comparing the volume of different bags and brands.

Measuring the volume of a backpack using a 3D scanner, for instance, could be more accurate, but scanners are hard to come by, especially for ordinary users. Therefore, it is necessary to rely on simple and accessible methods like measuring the length, width, and height of the backpack.

In the following section, we look at the tools you need to accurately measure the volume of a backpack.

Process and Required Tools

To measure the size or capacity of your backpack, you will need three things:

  1. A tape measure
  2. A flat surface
  3. A calculator or smartphone with an app that allows you to calculate cubic meters.

To start measuring your backpack, place it on a flat surface or table that is parallel to the ground. Make sure to leave all zippers open and close all outside pockets of the bag. This allows you to get an accurate measurement of only the main storage compartment of your backpack.

Suppose you have an internal-frame hiking backpack with several compartments and nooks that would make it challenging to measure accurately. In this case, you can break it down into its components: main compartment, sleeping bag compartment, and other small compartments such as hip belt pouches and mesh pockets. Measuring each of these parts separately will give you a better idea of how much your backpack can hold.

Regardless of whether some companies fill bags with pellets or use small measuring tools to calculate the usable space when determining the size of their bags; however, here we recommend our method to our readers as simple and easy.

Next, it is time to measure each dimension:

  • Length: Measure from top to bottom along one vertical side of the backpack
  • Width: Measure across from one side seam to the other
  • Height: Measure from front to back to find the total depth

Combine these three dimensions by multiplying them together—length x width x height = total volume. In some cases, however, the result may not be accurate because of curved edges or oddly shaped compartments.

Imagine a cake recipe where you square the butter before adding it to the mix, or imagine that you can easily calculate the surface area of a flattened paper bag using multiplication. In the same way, linear dimensions are simply individual metrics that need to be multiplied together to calculate the total volume of an object.

Having explained the process and required tools for measuring backpack volumes, we’ll now look at converting cubic measurements into liters.

Key Takeaway

Measuring the size or capacity of a backpack is easy if you have the right tools and know-how. To accurately measure your backpack, you will need a tape measure, a flat surface, and a calculator or smartphone with an app that can calculate cubic meters. It's important to place the backpack on a flat surface, leave all zippers open, and close the outside pockets before you measure.

If the backpack has multiple compartments, it's best to measure each compartment separately to increase accuracy. Once you have the dimensions, simply multiply them together to calculate the total volume of the backpack in cubic meters. If you convert the cubic meters into liters, you can more easily compare the sizes of different backpacks or brands.

Converting Cubic Measurements to Liters

Measuring the volume of a backpack in liters is not only more accurate but also an international standard. To do this, we need to convert cubic measurements into liters using the correct formula. While this process is generally straightforward, there are some nuances.

Let's say you have a backpack with dimensions of 40cm x 30cm x 20cm. To find the volume in cubic centimeters, you would multiply these values:

40cm x 30cm x 20cm = 24,000cm³

To convert cubic centimeters to liters, divide by 1000:

24,000 ÷ 1000 = 24L

Your backpack therefore has a volume of 24 liters.

Note that while this formula works well for rectangular shapes, other shapes may require a different approach.

Let's delve into the specifics of this conversion formula and examine some other examples.

The conversion from cubic meters to liters is simple—one cubic meter is equal to 1,000 liters. For example, if you have a backpack that measures 0.5m x 0.3m x 0.2m (which equals a total volume of 0.03 cu m), you can calculate the capacity in liters as follows:

Total volume (in cu m) x 1000 = Capacity (in liters)

0.03 x 1000 = 30 L

Here's another example: let's say you're measuring the interior of a round backpack with a diameter of 45cm and a depth of 35cm. You first need to calculate the volume by using this formula:

Volume = πr²h

where r is half the diameter and h is the height/depth

π(45/2)² x 35 = 63,615cc

To convert cubic centimeters to liters, divide by 1000:

63,615 ÷ 1000 = 63.6 L

Note, however, that when using the standard volume formula (length x width x height), the resulting volume is not always accurate as backpacks often have rounded edges. This can result in the measured capacity being higher than the actual space available in the backpack would suggest.

To address this issue and ensure accuracy in measuring the volume of backpacks, manufacturers use different methods and techniques.

Conversion Formula and Illustrative Examples

As mentioned earlier, the calculation of backpack volume in liters is done by converting cubic measurements into liters. The conversion is simple - just divide the total volume (cubic meters or cubic centimeters) by 1000 to get the capacity in liters.

As an example, let’s take a backpack measuring 65cm x 40cm x 25cm (which equals a total volume of 65,000 cc). We'll use the same formula as before:

Total volume (in cc) ÷ 1000 = Capacity (in liters)

65,000 ÷ 1000 = 65 L

Another example is a small shoulder bag with dimensions of 20cm x 15cm x 10cm (which equals a total volume of 3000cc). Again we use the same formula:

Total volume (in cc) ÷ 1000 = Capacity (in liters)

3000 ÷ 1000 = 3 L

There are also some online calculators that can help you convert cubic measurements to liters, especially for non-rectangular shapes.

Think of it this way: if you have a container filled with water, its total volume would be measured in liters. But if you want to know the capacity of the container, you would measure it in liters that it can hold. Similarly, the volume of a backpack is measured in liters because its capacity is determined by this measurement.

However, you should remember that despite this simple formula and easy conversion process, there are other factors that you need to consider when choosing the right backpack for your needs.

As we discussed in the previous section on fitting measurements to unusual backpack shapes, non-rectangular or unconventional backpack designs require different methods for measuring volume. Additionally, external pockets and material characteristics can affect the actual space available in a backpack.

In addition, manufacturers use different techniques to measure the volume of their backpacks such as filling them with small pellets or only measuring compartments with zippers. This makes comparisons between backpacks difficult and underlines how important it is to consider practical utility as a key factor when choosing the right backpack.

Choosing a backpack based on its volume alone would be like choosing a water bottle based only on the amount of water it can hold – it wouldn't necessarily indicate whether it's practical or suitable for your specific needs.

Therefore, it is important that you know how to measure the volume of a backpack in liters when choosing a new backpack.

Common Backpack Capacities and What They Mean

Backpacks are an essential item for anyone who travels a lot, whether for school, work, or outdoor activities. However, choosing the right backpack with the right capacity can be overwhelming. The volume of a backpack is usually measured in liters and ranges from 15 liters to over 60 liters. It's important to understand what these capacities mean before choosing a backpack that suits your needs.

Small backpacks usually have a capacity of less than 20 liters and are ideal for everyday use. They offer enough space to carry your essentials such as wallet, phone, snacks, and a water bottle. Small backpacks are perfect for short commutes to work or school or running errands around town.

Medium-sized backpacks typically have a capacity range of 25-30 liters. They are suitable for activities such as day hikes or overnight trips where you need to pack a little more than just your daily essentials. A medium-sized backpack has space for extra layers of clothing, food, water bottles, and other gear you need for outdoor activities.

Longer excursions or camping trips lasting several days require large backpacks with a capacity of 35 liters or more. These backpacks have space for all the equipment you need for multi-day trips outdoors. Large backpacks are also designed to carry heavier and bulkier equipment like camping tents, stoves, first aid kits, and sleeping bags.

Remember that the size of the backpack often correlates with its weight. Be sure to stay away from oversized backpacks that are heavy before they are filled with gear as they can cause discomfort and injury. Also, make sure that the backpack fits properly so that most of the weight is on the hips and not on the shoulders or back muscles.

Different professions require certain types of backpacks. For example, a photographer needs a camera backpack with special compartments and adjustable padding to protect and carry their camera lenses safely. These backpacks are typically larger than normal backpacks and offer a variety of compartments.

The capacity of backpacks is comparable to the number of seats in cars. Just as the number of seats determines how many people can ride, the volume of a backpack determines how much gear it can hold. Similar to how smaller cars have lower fuel consumption and are cheaper to buy, smaller backpacks are easier to carry, less bulky, and more affordable.

Understanding what the different capacities mean will help you choose the right backpack size for your needs. However, choosing the right volume is only part of finding the perfect backpack. When choosing the right backpack, you also need to consider other factors such as weight distribution, structure and fit adjustment mechanisms, ventilation systems, and more.

Adjusting Measurements for Unusual Backpack Shapes

Not all backpacks are the same, and some have unusual shapes that make it difficult to measure their volume using conventional methods. For example, backpacks with rounded edges or backpacks made of flexible material are difficult to measure accurately.

One method that you can use is to fill the backpack with packing paper or tissue until it is full, and then pour the contents into a large container with marked measurements. Note the volume of displacement and subtract this amount from the total volume of the container to get an accurate measurement of your backpack's capacity.

Another method is to divide your backpack into smaller sections and measure each section separately before adding them up. This works especially well for backpacks with multiple compartments and pockets. Also take into account the space lost due to overlaps between the different sections.

While it may be tempting to estimate the approximate volume of your backpack, using one of these techniques will give you a more precise result. Remember that inaccurate measurements can lead to overpacking or underpacking, which can affect your comfort and safety on long hikes or trips.

Measuring backpack capacities with unusual shapes is like solving a puzzle. It requires patience, creativity, and ingenuity to find the best solution.

Now that we've discussed how to adjust measurements to unusual shapes, let's move on to techniques for considering pockets and rounded edges.

Techniques to Account for Pockets and Rounded Edges

Backpacks usually have pockets and compartments that make it difficult to determine their capacity. The most common problem is calculating the space lost due to rounded corners and edges. Since they don't follow straight lines, these areas result in dead space that cannot be used for storage.

One method is the so-called "water displacement." First, fill a bathtub partially with water and then submerge your backpack. Push it down until it is completely submerged and all pockets are full. Wait for the air bubbles to escape before removing the backpack from the water. Measure the amount of water displaced in liters, which is equivalent to the volume of the backpack. Subtract the space taken up by the items in the pockets.

Another technique uses a garbage bag. Place your empty backpack in a large trash bag that reaches to the top of the straps. Seal off the bag as tightly as possible, use a vacuum cleaner to suck out all air from within, and fold the bag around the pack. This method can help determine how much extra space you have in your backpack by measuring the excess material and comparing it with the manufacturer’s specifications.

If you are looking for a quick and easy solution to measure the volume of the outer pockets of your backpack, you should stuff them with materials such as foam blocks before measuring. This works best if you don't have specific shapes or sizes of items that need to fit into your compartments.

Remember that not all manufacturers calculate the capacity of backpacks using the same method. So it's important that you only compare apples to apples when considering different models. While some only look at the main compartments, others may include all available pockets and pouches. Depending on where you measure, some brands may also give different values than those resulting from calculating the total volume according to traditional formulas.

By following these techniques for measuring backpacks with unusual shapes and accounting for empty spaces due to rounded edges or pockets, you can get accurate measurements no matter how complicated or unusual the shape of your gear.

About the author

Keith is a one bag traveler and the owner of Backpacks Global. His go to backpack is the Osprey FarPoint 40.

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