Have you ever experienced this?

Two backpacks are both rated at 20L, yet one can hold a laptop, charger, water bottle, and jacket while staying perfectly organized. The other is barely half full before the zipper starts to feel like it's under pressure.

So, why can two 20L backpacks feel so different in actual use?

The answer isn't just capacity.

What really determines how much a backpack can carry includes space utilization, bag structure, opening design, internal organization, and expandability.

In other words:

Capacity tells you how much space you have. Design determines how much of that space you can actually use.

That's why some 20L backpacks can feel like they have the capacity of a 30L bag.

1. 20L Doesn't Always Mean 20L of Usable Space

L (liter) represents the theoretical volume of a backpack.

But theoretical capacity ≠ usable capacity.

Imagine two storage boxes that are both 20L.

One has a large opening and a clean, well-organized interior.

The other is divided by multiple panels and has a narrow opening.

They may have the same stated capacity, but the actual packing experience can be completely different.

The same applies to backpacks.

When the interior is relatively continuous and well structured, different items can fit together and make better use of available space.

But when the interior is overly divided, you may end up with:

Compartments that are individually too small, while the overall space still contains unused areas.

That's why, when choosing a backpack, you shouldn't only look at its capacity.

Pay attention to:

Space utilization.

2. The First Factor That Determines Capacity: Opening Design

When shopping for a backpack, many people focus on:

"How many liters is it?"

But there's another question that's just as important:

"How easy is that space to use?"

A 20L backpack with a narrow top opening can become difficult to access once it's packed.

You may know that something is inside, but still struggle to reach it.

Items placed at the bottom are especially difficult to access because you often have to remove everything on top first.

That's where a wide-opening design becomes important.

3. L-Shaped Wide Opening: Making 20L Feel More Accessible

The Nayo Smart Herman Pro features an L-shaped wide opening, allowing the main compartment to open much wider.

Compared with a traditional top-loading backpack, this makes the interior much easier to see and access.

Once opened, you can quickly see:

• Laptop accessories 
• Chargers 
• Clothing
• Everyday essentials
• Remaining space inside the main compartment

Instead of reaching blindly into a narrow opening, you can interact with the interior more directly.

This is especially useful for commuting and mobile work.

For example:

Home → Café

Once you sit down, you can easily access your laptop, charger, mouse, and other work essentials.

Or at airport security, when you need to take out your laptop quickly, you don't have to unpack the entire bag.

So the L-shaped opening doesn't actually increase the stated capacity.

4. Half Roll-Top Design: Expand the Capacity When You Need It

Another key feature of the Herman Pro is its:

Half Roll-Top design.

Traditional backpacks usually have a relatively fixed top section.

A half roll-top design gives you more flexibility.

For everyday commuting

Keep the bag compact when you're carrying your usual essentials.

For after-work plans or short trips

When you suddenly need to carry more items, you can make use of the additional expandable space.

The benefit of a half roll-top isn't simply "more capacity."

It's:

More space when you need it, without carrying a larger bag when you don't.

That's the key difference between fixed capacity and expandable capacity.

5. Half Roll-Top + L-Shaped Opening: One Helps You Pack, the Other Helps You Access

These two features solve different problems.

Half Roll-Top

Expansion

Release additional space when you need to carry more.

L-Shaped Wide Opening

Accessibility

Open the main compartment wider for easier packing and access.

Together, they answer two different questions:

The half roll-top answers: "Can I fit a little more?"

The L-shaped opening answers: "Can I easily access what I've packed?"

This combination is one of the reasons the Herman Pro can feel like it offers more usable capacity than its stated volume suggests.

6. Dedicated Laptop Compartment: Give Your Most Important Device Its Own Space

For modern commuters, a laptop is often one of the most important items they carry.

The Herman Pro features a dedicated laptop compartment, keeping your computer separate from the main compartment.

This helps:

· Reduce direct contact with other belongings

· Improve laptop accessibility

· Keep the main compartment more flexible

· Prevent your laptop from getting mixed in with chargers, keys, and other items

Your laptop has its own space, while the main compartment remains available for everything else.

7. Digital Organization: Prevent Small Items from Wasting Space

Chargers, cables, mice, earbuds, power banks, and other accessories may be small, but they can quickly make a backpack messy.

If everything is simply thrown into the main compartment, it can soon become a:

"Cable Black Hole."

The Herman Pro uses dedicated organization areas to give frequently used digital accessories their own places.

The goal isn't simply to add more pockets.

It's to:

Reduce search time while improving space utilization.

Because an organized space can often feel much more spacious than a messy space of exactly the same size.

8. Six Factors That Really Determine Backpack Capacity

So, the next time you choose a backpack, don't look at liters alone.

Consider these six factors:

1. Space Utilization

Are there large areas of space that are difficult to use?

2. Opening Design

Can you easily see and access the interior?

3. Bag Shape

Is the internal space structured efficiently?

4. Storage Organization

Do the compartments help you organize, or do they divide the space into unnecessarily small sections?

5. Expandability

Can the capacity adapt to different needs?

6. Accessibility

Can you still find things quickly when the bag is fully packed?

Together, these factors determine what we might call:

Usable Capacity.

9. Is 20L Enough? It Depends on How You Live

There is no universal answer to whether 20L is "enough."

It depends on what you carry every day.

Lightweight Commuting

If you typically carry:

Laptop + Charger + Wallet + Phone + Water Bottle

a well-designed 20L backpack may be more than enough.

Mobile Work

If you also carry:

Mouse + Notebook + Headphones + Power Bank

then internal organization and opening design become much more important.

Commuting + Weekend Trips

If you need extra room for a jacket, camera, or other personal belongings, then expandability becomes particularly useful.

Instead of automatically choosing a larger backpack, first ask:

What do I actually need to carry every day?

10. Why Bigger Doesn't Always Mean Better

When people feel that their backpack doesn't have enough space, the first reaction is often:

Buy a bigger one.

20L becomes 25L.

25L becomes 30L.

But a larger backpack can also mean:

• More bulk
• More weight to carry
• More room for unnecessary items
• A greater chance of internal clutter

If you only need around 20L for your everyday routine, a backpack that is expandable, easy to access, and efficient with its space may be more practical than a fixed 25L backpack.

So:

More capacity doesn't always mean more efficiency.

What matters is:

Right Capacity + Smart Design

Conclusion: Real Capacity Means More Room, Better Access, and Flexibility

So, why can some 20L backpacks feel like 30L?

The answer isn't necessarily that they actually hold 30L.

It's that they make better use of the space they have.

The Nayo Smart Herman Pro achieves this through several key design elements:

Half Roll-Top Design
→ Expand the space when you need it.

L-Shaped Wide Opening
→ Open the main compartment wider for easier packing and access.

Dedicated Laptop Compartment
→ Give your laptop its own protected storage space.

Digital Organization
→ Keep chargers, mice, earbuds, and other small accessories organized.

Ultimately, the goal isn't simply to make a backpack bigger.

It's to make every liter count.

The real capacity isn't just how much you can fit. It's how efficiently you can use every liter.

A truly well-designed backpack doesn't necessarily need more capacity.

It needs to let you:

Fit what you need, find what you need, and make room for a little more when you need it.