One of the most frustrating experiences when buying a laptop case is receiving your purchase only to find it doesn't fit. Maybe it's too tight, leaving you wrestling to insert your laptop. Perhaps it's too loose, offering little protection as your device slides around inside. The culprit is almost always the same: confusion between screen size and actual laptop dimensions.
This seemingly simple issue trips up countless buyers. Laptop cases are marketed using screen sizes – 13-inch, 15.6-inch, 17-inch – but these measurements only tell part of the story. Your laptop's actual physical dimensions can vary significantly from other laptops with the same screen size. This guide will show you exactly how to measure your laptop and interpret sizing information so you never order the wrong case again.
Understanding the Screen Size Problem
Screen size, measured diagonally from corner to corner of the display, is how laptops are categorised. However, this measurement doesn't account for the bezel (the frame around the screen) or the laptop's body, which extends beyond the screen area. A 15.6-inch Dell may have completely different external dimensions than a 15.6-inch HP or ASUS.
Modern laptops with slim bezels can have significantly smaller bodies than older models with the same screen size. A 2025 laptop with a 15.6-inch screen might actually be closer in size to a 2019 laptop with a 14-inch screen. This is why relying solely on screen size when choosing a case is problematic.
A MacBook Air 13-inch and a Dell Inspiron 15 with a 15.6-inch screen have only about 5cm difference in width, even though their screen sizes differ by nearly 3 inches. Bezel size makes a significant difference.
What You'll Need
Measuring your laptop requires minimal equipment:
- A measuring tape or ruler: Ideally one that measures in centimetres and millimetres for precision
- A flat surface: Ensure your laptop sits completely flat for accurate measurements
- Paper and pen: To record your measurements
Step-by-Step Measuring Guide
Step 1: Measure the Width
Close your laptop completely. Place it on a flat surface with the front edge (where you'd open it) facing you. Measure from the left edge to the right edge at the widest point. Most laptops are widest at their back edge where the hinges are, though some designs may have the same width front to back.
Record this measurement in both centimetres and inches if possible. If your measuring tape only shows one unit, you can convert later (1 inch = 2.54 centimetres).
Step 2: Measure the Depth
With your laptop still closed and flat, measure from the front edge to the back edge. This measurement is often called "depth" and is particularly important for bags with structured laptop compartments. A case might be wide enough but not deep enough to accommodate your laptop.
Always measure with your laptop closed. Open laptops can be misleading because the screen may extend beyond the base. The case needs to fit your laptop as it will be when stored inside – closed.
Step 3: Measure the Thickness (Height)
This is the measurement most often overlooked, yet it's crucial for snug-fitting sleeves and compact bags. Measure from the bottom of your laptop (when sitting flat) to the highest point when closed. This is usually near the hinges, where the screen and keyboard sections meet.
Don't forget to account for any components that protrude, such as raised rubber feet on the bottom or elevated hinge designs. Measure at the thickest point to ensure your case will accommodate the entire device.
Step 4: Account for Accessories
If you typically keep accessories attached to your laptop, factor these into your measurements. A laptop with a permanently attached privacy screen, keyboard cover, or protective shell will have different dimensions than the base laptop. Measure with these items in place if you plan to store the laptop with them attached.
Recording and Using Your Measurements
Create a simple reference card with your measurements:
- Width: ___ cm / ___ inches
- Depth: ___ cm / ___ inches
- Thickness: ___ cm / ___ inches
- Screen size: ___ inches (for reference)
- Laptop model: ___
Keep this information saved on your phone or written in your wallet. When shopping for cases, you can quickly compare your dimensions against product specifications.
Interpreting Case Specifications
Internal vs. External Dimensions
Quality laptop case listings provide internal dimensions – the actual space available for your laptop. Some listings only show external dimensions, which include the case's walls and padding. Always look for internal dimensions when comparing. If only external dimensions are available, assume you'll lose 1-3 centimetres on each dimension due to padding and case construction.
Ideal Fit Parameters
For optimal protection and ease of use, look for cases where:
- Width and depth: Allow 5-15mm of clearance beyond your laptop's measurements. This provides wiggle room for easy insertion while maintaining a snug protective fit.
- Thickness: Allow at least 5mm extra, more if you want room for a thin charger or mouse inside the same compartment.
Avoid cases that are too roomy – excessive space allows your laptop to move around, reducing protection and potentially causing scratches from interior fabric contact.
Don't assume a case labelled "13-inch" will fit all 13-inch laptops. Always check the internal dimensions against your measurements. Some cases run small or large, and laptop dimensions vary significantly within the same screen size category.
Special Considerations
Gaming Laptops
Gaming laptops often have larger bodies than their screen size suggests due to powerful cooling systems and full-size keyboards. A 15.6-inch gaming laptop may need a case designed for 17-inch standard laptops. Measure carefully, as these laptops also tend to be thicker.
2-in-1 and Convertible Devices
Convertible laptops that transform into tablets may have unusual shapes or protruding hinges. Measure in the laptop configuration (screen closed against keyboard) since this is how you'll typically store the device.
MacBooks
Apple laptops have standardised dimensions that rarely change between models of the same screen size. However, be aware that MacBook Air and MacBook Pro with the same screen size have different dimensions – the Pro is typically larger. Also note that older Intel MacBooks may differ from current M-series models.
What To Do When Measurements Are Borderline
If your laptop measurements fall right at the edge of a case's specifications, consider these factors:
- Sleeve vs. bag: Sleeves need closer tolerances than bags with dedicated laptop compartments
- Padding thickness: Thicker padding compresses slightly, offering a bit more flexibility
- Return policy: If you're between sizes, choose the larger option and ensure the seller accepts returns
When in doubt, contact the seller or manufacturer with your exact measurements. Reputable companies will confirm whether their case will fit your specific laptop model. This is especially useful for premium purchases where fit is critical.
Final Thoughts
Taking five minutes to properly measure your laptop can save you the frustration and expense of ordering the wrong case. Keep your measurements handy, always verify internal dimensions when shopping, and don't rely solely on screen size categories. With accurate measurements in hand, you can shop confidently, knowing that your new case will fit perfectly from the moment it arrives.