13 Common Things That Are About 40 Centimeters Long

Imagine trying to hang a picture frame without a tape measure. You hold up the frame, squint, step back, and hope you’ve guessed the spacing right. In moments like these, having a mental library of everyday objects and their sizes can be surprisingly useful. One of the most practical lengths to recognize is 40 Centimeters Long—a measurement that quietly appears in tools, household items, sports equipment, and even in the natural world. Once you know how long 40 centimeters is, you’ll start spotting it everywhere.

How Long is 40 Centimeters?

Forty centimeters equals just under 16 inches, or a little more than the length of a standard laptop keyboard. It’s longer than a standard ruler (30 cm) but shorter than most people’s arm from shoulder to wrist. Picture two average bananas lined up end-to-end—that’s roughly 40 centimeters.

Understanding this length helps you visualize proportions, make quick estimations, and appreciate why manufacturers, designers, and even athletes often rely on it as a practical standard.

1. A Medium-Sized Acoustic Guitar Neck

Guitars come in all shapes and sizes, but the neck of a medium-sized acoustic guitar often measures close to 40 centimeters. The neck is the part you hold and press the strings against, so its length directly influences how easy or hard the instrument is to play.

For beginners, a guitar with a shorter neck around this size can feel more comfortable, allowing smoother chord changes and less strain on the fingers. Interestingly, some travel guitars are specifically designed with necks around 40 centimeters long to strike a balance between portability and playability.

Fun fact: Antonio Torres Jurado, often considered the father of the modern guitar, experimented with neck lengths in the 19th century to refine tone and comfort—his designs still inspire guitar makers today.

2. A Kitchen Rolling Pin

A classic rolling pin used for baking cookies, pies, or pizza dough typically stretches to about 40 centimeters. This length is perfect: long enough to roll out even sheets of dough without being so large that it becomes unwieldy.

Cooks and bakers often prefer this size because it fits comfortably across most standard countertops and dough sizes. Professional pastry chefs sometimes opt for longer pins, but the 40-centimeter range remains the most practical for home use.

Here’s a bit of trivia: in France, traditional rolling pins are tapered at the ends, and their standard length—yes, around 40 cm—is designed to give bakers finer control when shaping delicate pastries.

3. A Small Tennis Racket for Kids

Children learning tennis often start with rackets measuring around 40 centimeters in length. These shorter rackets are lightweight, manageable, and designed to help kids develop swing techniques without fatigue.

The length matters because it determines reach, power, and control. For tiny beginners, anything much longer would be too heavy and discourage practice. Manufacturers intentionally make youth rackets around this size to balance ergonomics and performance.

4. A Desk Lamp Arm

If you’ve got a desk lamp with an adjustable arm, chances are one of its sections is right around 40 centimeters long. That length is ideal for positioning light exactly where you need it—whether over a laptop, sketchbook, or novel.

Engineers design lamp arms with ergonomics in mind, and 40 centimeters allows for versatile reach without creating too much leverage that might tip the lamp over. It’s also just the right span to clear most desktop setups without clutter.

Did you know? The anglepoise lamp, invented in 1932, revolutionized task lighting with its spring-balanced arms—each carefully measured. The middle section of many of those designs? Around 40 cm.

5. A Cat’s Tail (on Larger Breeds)

Nature often surprises us with its own use of practical lengths. The tail of a large domestic cat, like a Maine Coon, can measure around 40 centimeters. That tail isn’t just for show—it’s an essential balancing tool when leaping or climbing, and it also helps cats communicate mood.

For example, a cat with its 40 cm tail held high is showing confidence, while one with it tucked low is signaling fear or submission. The sheer length is a product of evolution: the longer the tail, the better the balance.

Fun fact: The Guinness World Record for the longest domestic cat tail measured a whopping 44.66 centimeters, belonging to a cat named Cygnus, whose tail was almost as long as his body.

6. A Carry-On Suitcase Width

If you’ve ever wheeled a carry-on bag through a busy airport, you’ve probably been guided by an airline’s strict size restrictions. The width of many standard carry-on suitcases comes in at about 40 centimeters.

This width matters because it ensures the bag can slide comfortably into overhead compartments and under seats while still offering enough packing space for essentials. It’s a sweet spot between convenience and capacity.

Trivia to tuck in your bag: The very first rolling suitcase was invented in 1970 by Bernard Sadow, inspired by watching an airport worker roll heavy equipment on a dolly. His prototype? Roughly the same width as today’s 40 cm designs.

7. A Standard Skateboard Deck

A skateboard deck—the flat board where riders stand—typically measures 40 centimeters across in width when you look at its total wheelbase and usable surface. While the length of most skateboards is longer, the 40 cm dimension often pops up in the parts of the deck that matter most for balance and trick performance.

This size provides a balance of stability and maneuverability. Riders need enough board width to feel secure while still being able to flip, spin, or pivot. For beginners, this sweet spot often helps with confidence and control.

Here’s something cool: Skateboarding became so popular in the 1970s that companies experimented with deck shapes and sizes. Yet, across decades of evolution, a section of roughly 40 cm remains central to designs for balance.

8. A Car Steering Wheel Diameter

Most modern car steering wheels measure around 40 centimeters across from edge to edge. This size strikes a balance between control and comfort, giving drivers enough leverage to steer smoothly without making the wheel too bulky.

The measurement is important for ergonomics and safety. A wheel too small can feel twitchy and difficult to handle, while one much larger might restrict movement, especially in compact cars.

Fun fact: Formula 1 steering wheels are much smaller—often only 28–30 cm—but are packed with buttons, switches, and screens. For everyday vehicles, though, 40 cm is the sweet spot that’s stood the test of time.

9. A Violin Bow

The bow used to play a violin is often around 40 centimeters long, especially for student-sized instruments. This length allows the player to draw smooth, even sounds across the strings without excess weight or awkward handling.

Bow length matters for precision and tone production. Too short, and the musician struggles to sustain notes; too long, and it becomes clumsy for younger learners. Makers carefully craft bows with this practical measurement to balance finesse and control.

Did you know? Traditional bows are made with horsehair—usually from the tail of a horse—and one bow can contain over 150 individual hairs, all stretched along that ~40 cm stick.

10. A Shelf Depth in a Bookcase

The depth of many bookcase shelves measures close to 40 centimeters, making them ideal for holding large hardcovers, photo albums, or storage boxes. This dimension gives plenty of room for oversized books that wouldn’t fit on shallower 20–25 cm shelves.

This size matters for functionality: deeper shelves can hold bulkier items without sagging or overhang. Designers also choose this dimension to maximize space efficiency in living rooms and offices.

Fun trivia: The Library of Congress—the largest library in the world—has shelving designed with varying depths, but many reference collections use a depth of around 40 cm to house oversized historical volumes.

11. A Toddler’s Height at 3–4 Months Old

Human development offers another fascinating reference: many babies measure about 40 centimeters in length at birth and quickly grow beyond it in just a few weeks. By three to four months, their torso length alone is often around 40 cm.

This length is medically significant because pediatricians use it to track healthy growth. Measuring head-to-toe length or torso span ensures the baby is developing properly. Baby clothing sizes are also often based on this measurement.

Interesting fact: The smallest recorded newborn, weighing just 245 grams, was only slightly longer than 40 cm—and yet survived to become a healthy child, demonstrating the resilience of human life.

12. A Professional Chef’s Knife in Total Length

A chef’s knife, the workhorse of every kitchen, usually measures around 40 centimeters from tip to handle end. The blade itself is often 20–25 cm, while the handle adds the remainder. This overall size provides balance, allowing chefs to slice, chop, and dice with control.

Length matters because it gives leverage for cutting large vegetables or meats without being unwieldy. A shorter knife can feel limiting, while a much longer one can intimidate or tire out the cook.

Trivia: The Japanese “gyuto,” a style of chef’s knife, often lands around this length. It’s prized worldwide for its precision, durability, and ergonomic design.

13. A Desktop Computer Keyboard

A standard full-sized computer keyboard often spans close to 40 centimeters across. This width accommodates all 104 keys comfortably, including the number pad, function row, and arrow keys.

The size is important for typing accuracy and ergonomics. Narrower keyboards may save desk space but often cause strain as hands are cramped closer together. Around 40 cm provides a comfortable width that suits most desk setups.

Fun fact: The first commercially successful computer keyboard, built for the IBM Model M in 1984, was close to today’s dimensions—proving that 40 cm has been a practical standard for decades in digital design.

Visualizing 40 Centimeters in Everyday Life

Not everyone walks around with a ruler. So how can you quickly imagine 40 cm without a measuring tool?

• Think of a standard laptop screen width—many fall right near 40 cm.
• Picture two large dinner plates placed side by side.
• Imagine the span of your forearm from elbow to fingertips—for many adults, that’s close.
• Stack four average smartphones end-to-end, and you’re right there.

If you’re in a pinch and need to measure, try using these reference points. For DIY projects or home organization, knowing these mental benchmarks can save you a trip to find a measuring tape.

Why Knowing 40 Centimeters Matters

Understanding this length isn’t just trivia—it’s practical knowledge. It helps you:

• Estimate furniture dimensions when shopping without a tape measure.
• Choose the right sports equipment for children.
• Gauge storage and packing space while traveling.
• Appreciate how design, ergonomics, and even biology often converge around this handy measurement.

Conclusion

Now that you’ve seen just how common 40 centimeters is, you might start noticing it in unexpected places—your gadgets, your pets, even your kitchen drawer. Recognizing this length helps sharpen your spatial awareness, making everyday decisions easier and sometimes even saving you from frustration.

Here’s a fun challenge: Take a walk around your home and see how many things you can find that measure close to 40 cm. From a cutting board to a decorative pillow, you may be surprised at just how often this humble measurement appears.

In the end, understanding 40 centimeters is like adding another tool to your mental toolkit. It helps you see the world not just in objects, but in proportions—and that’s a skill worth carrying everywhere.