Backpack Capacity Explained: Litres vs Usable Space

Backpack capacity tells you about storage volume, not how much weight a person or a pack should carry. To compare rucksacks properly, establish what the stated volume includes, how it was measured and whether the actual equipment fits through the openings and inside the usable compartments.

For project buyers, a capacity number is a useful starting point, but it is not a complete acceptance requirement. A practical evaluation separates the advertised volume, the geometry of the storage spaces and the packing result with the intended contents. This guide explains that distinction without assigning an unverified load limit to any AKMAX model.

Keep volume, dimensions and weight separate

Litres describe volume. Centimetres describe lengths such as height, width and depth. Kilograms describe mass. These measurements answer different questions and should occupy different fields in a comparison sheet.

A listing with generous volume can still be unsuitable for a particular rigid item. Conversely, a compact item can be heavy enough that volume is not the main selection issue. Treat carrying suitability as a separate review using the actual system, user requirements and verified product guidance.

Ask what the capacity figure includes

Find out whether the quoted volume describes the main bag, the main bag plus fixed pockets, an extended configuration or several separate bags supplied together. A main rucksack and a detachable smaller pack remain separate spaces even when their volumes are added in a commercial description.

The AKMAX Rucksacks & Backpacks collection contains both individual packs and multi-component systems. Identify the exact configuration before comparing headline capacity figures. Do not assume that accessories visible in a photograph contribute to the supplied storage.

A useful question is: “Which compartments and supplied components are included in this figure?” Ask for the answer in writing when volume is important to the purchase. If the basis is not known, label the value as the supplier's stated capacity rather than presenting it as independently measured.

A shared measurement method makes comparisons clearer

The public scope of ASTM F2153-07(2018), Measurement of Backpack Capacity, distinguishes unextended and extended capacity and describes a consistent basis for comparing pack volumes. Its scope excludes storage areas that are not completely enclosed by fabric. This illustrates why the measurement basis matters.

Citing that method does not establish that an AKMAX pack has been tested to it. If a procurement specification requires a particular method, ask whether a corresponding measurement record is available and what configuration it covers. Do not describe an informal packing trial as a standardized capacity test.

For preliminary comparison, a clearly identified nominal figure can still be useful. Keep it separate from a verified measurement so the purchasing team can see which conclusions the available information supports and which questions remain open.

Do not turn three dimensions into an exact soft-pack volume

Multiplying height, width and depth calculates the volume of a rectangular box. A soft rucksack is not necessarily that box. Its shape, compartment divisions and the way dimensions were taken must be understood before drawing a capacity conclusion.

Ask whether the dimensions are external or internal, whether they apply to the main compartment or the complete assembly, and whether the bag was empty or filled. Also identify whether the lid, extension or exterior pockets were included. Measurements taken under different conditions can describe different things without either being a useful direct comparison.

The current AKMAX ALICE Large 75L Rucksack listing expressly identifies 75L as its nominal commercial capacity designation and lists main-compartment dimensions separately. It also identifies the standard complete configuration. Preserve those distinctions rather than presenting a calculation from the listed dimensions as a new verified capacity.

Check the largest item before filling the remaining space

Start with any item whose shape cannot easily change: a protective case, a rigid container or another bulky piece of ordinary field equipment. Record its dimensions in the condition in which it will actually be carried, including any required cover or case.

Then check the opening as well as the interior. An object that appears to fit within the compartment's widest dimensions may still be difficult to insert or remove through a narrower opening. Confirm the proposed orientation and whether the normal closure can be used without forcing it.

Do not assume that soft items can always fill every gap around rigid objects. Use the actual contents or agreed representative items for the evaluation. Where a substitute is used, record its limitations instead of treating it as an exact copy of the intended equipment.

Compare usable spaces, not just total litres

Consider an illustrative comparison: one proposal describes a single 60L bag, while another describes a 40L main bag plus a separate 20L pack. The totals are numerically equal, but the second arrangement does not create one continuous 60L compartment. A large item that needs the main compartment may decide the comparison.

This example is not a specification for an AKMAX product. It shows why the buyer's item list should be assigned to actual compartments rather than compared only with an aggregate total.

Also identify which items must remain accessible without unpacking everything else. A packing arrangement that technically contains all the equipment may still be inconvenient for the intended routine. Record access requirements as such; they are not additional litres and should not be hidden inside the capacity target.

Run a repeatable packing evaluation

Use a controlled sample configuration and the same contents when comparing candidates. Begin with the normal supplied components, not an expanded arrangement assembled from unquoted accessories. Follow the product instructions and stop if closure or insertion requires forcing parts.

• Identify the pack model, revision and included bags or pouches.
• List the test contents, their cases and any representative substitutes.
• Record which item goes in each compartment.
• Check insertion, normal closure and removal of the largest items.
• Record whether access requires moving other contents.
• Note any requested accessories separately from the standard configuration.
• Record the packed assembly's mass separately from the fit result.

A successful packing trial answers a specific question: these contents fit this configuration in the recorded arrangement. It does not prove a maximum load rating, universal comfort or suitability for a different equipment list. Keep those conclusions separate in the evaluation report.

Write the purchasing requirement around the real need

If a specific item must fit, state its dimensions, protective packaging and access requirement. If a measured volume is mandatory, identify the measurement basis and configuration. If the objective is to carry a defined equipment set, provide that set as the practical reference instead of choosing an arbitrary litre figure alone.

Review the AKMAX rucksack supply and project procurement page for available platforms and the inquiry process. Include the proposed model, quantity, required contents and unresolved capacity questions. Custom configurations and any performance requirements need explicit confirmation.

The most useful capacity comparison connects the number to a defined storage arrangement and a real packing need. Select on what the complete system can demonstrably accommodate, while treating weight limits, user fit and performance evidence as separate decisions.