Keycap Dimensions | A Comprehensive Guide for Beginners

Understanding keycap dimensions is crucial for customizing mechanical keyboards. Keycaps are the plastic tops you press on your keyboard (letters, numbers, symbols). However, not all keycaps are created equal! This guide will unlock the world of keycap sizes with ANSI, ISO, JIS to find the perfect set for your keyboard. 

How Keycaps Are Measured?

Keycaps are measured in units, with each standard alphanumeric key being 1u (unit) in size. This unit measurement includes the width, length, and height of the keycap. Larger keys, like Enter or Shift, are multiples of 1u. Therefore, a 2u keycap is twice the size of a regular key. Sizes like 6.25u refer to the keycap's length. A 6.25u keycap is essentially six standard keys long with an extra quarter of a key added on.

Moreover, different keyboard layouts (full-size, tenkeyless, 60%) have specific key sizes. For example, the bottom row keys are usually 1.25u, while the spacebar is often 6.25u. Here's a visual guide to help you understand keycaps sizing: 

 

Related Article:

• What are Keycaps? An Inside Look At Keycaps

Keycap Dimensions Chart by Keyboard Layouts

The keycaps on your keyboard are more than just buttons - they play a big role in both the aesthetics and functionality of your typing experience. In the keyboards world, we can category different types of keycaps by their profiles. Different regions have adopted their own standards, resulting in variations in keycap sizes and arrangements. Let's explore the three most common layouts through the keycap size chart below:

Keyboard Layouts	Types of Keys	Dimensions
ANSI (most common)	Standard Alphanumeric	1u (varies in height)
	Backspace/Enter	1.5u - 2.25u (Enter can be slightly larger on some models)
	Shift (Left & Right)	1.25u - 2.75u (Left Shift can be larger)
	Ctrl, Alt, Fn	1u
	Modifier Keys (Caps Lock, Tab, Delete)	1u - 1.5u
	Function Keys (F1-F12)	1u (all usually same size)
	Spacebar	6.25u
ISO (Europe)	Standard Alphanumeric	1u (varies in height)
	Backspace	1.5u - 2.25u
	Enter	1u - 1.5u
	Left Shift	1.25u - 2.75u
	Right Shift	1u
	Ctrl, Alt, Fn	1u
	Modifier Keys (Caps Lock, Tab, Delete)	1u - 1.5u
	Function Keys (F1-F12)	1u
	Spacebar	6.25u
JIS (Japan)	Standard Alphanumeric	1u (varies in height)
	Backspace/Enter	1.5u - 2.25u
	Shift (Left & Right)	1.25u - 2.75u (left shift can be larger)
	Ctrl, Alt, Fn	1u
	Modifier keys (Caps Lock, Tab, Delete)	1u - 1.5u
	Special Key (Input Method)	1u (varies) - This key is used to switch between Hiragana, Katakana, and Roman characters
	Function Keys (F1-F12)	1u
	Spacebar	6.25u

ANSI Keycap Sizes

The ANSI layout reigns supreme in North America and pockets of Asia. It's the familiar layout you'll find on most personal computers, laptops, and gaming keyboards in these regions. The ANSI layout features a dedicated row of function keys (F1 - F12) positioned above the alphanumeric keys.

 

Cap	Unit Length	Row	Stabilizer
Esc	1u	R1
Tab	1.5u	R2
Caps Lock	1.75u	R3
Left Shift	2.25u	R4	Yes (2u)
Left Control	1.25u	R4
Left GUI	1.25u	R4
Left Alt	1.25u	R4
Spacebar	6.25u	R4	Yes (6.25u)
Right Alt	1.25u	R4
Right GUI	1.25u	R4
Right Menu	1.25u	R4
Right Control	1.25u	R4
Right Shift	2.75u	R4	Yes (2u)
Enter	2.25u	R3	Yes (2u)
Backspace	2u	R1	Yes (2u)

Note: Please note that there can be some variations depending on the specific keyboard model.

ISO Keycap Sizes

The ISO layout reigns supreme in Europe and some parts of South America. It's the standard layout you'll encounter on most personal computers and laptops sold in these regions. This layout features a dedicated row of function keys (F1-F12) positioned above the alphanumeric keys, similar to the familiar ANSI layout. 

However, the ISO layout introduces a key distinction with the addition of a key between Left Shift and Ctrl. This extra key is often used for symbols like Euro (€). Additionally, the Enter key size can vary slightly compared to ANSI keyboards.

 

Cap	Unit Length	Row	Stabilizer
Esc	1u	R1
Tab	1.5u	R2
Caps Lock	1.75u	R3
Left Shift	1.25u - 2.75u	R4	Yes (2u)
Left Control	1.25u	R4
Left GUI	1.25u	R4
Left Alt	1.25u	R4
Spacebar	6.25u	R4	Yes (6.25u)
Right Alt	1.25u	R4
Right GUI	1.25u	R4
Right Control	1u	R4
Right Shift	1.75u	R4
Enter	1u-1.5u	R3	Yes (1u or 1.5u)
Backspace	2u	R4	Yes (2u)

Note: Please note that there can be some variations depending on the specific keyboard model.

JIS Keycap Sizes

The JIS layout is primarily found in Japan. It's the standard layout on personal computers and laptops designed for the Japanese market. These keyboards cater to the specific needs of users who require the ability to input text in Hiragana, Katakana, and Roman characters.

 

Cap	Unit Length	Row	Stabilizer
Esc	1u	R1
Tab	1.5u	R2
Caps Lock	1.75u	R3
Left Shift	2.25u	R4	Yes (2u)
Left Control	1.25u	R4
Left GUI	1.25u	R4
Left Alt	1.25u	R4
Spacebar	6.25u	R4	Yes (6.25u)
Right Alt	1.25u	R4
Right GUI	1.25u	R4
Right Control	1.25u	R4
Right Shift	1.75u	R4
Enter	2.25u	R4	Yes (2.25u)
Backspace	1.5u	R1	Yes (1.5u)

Note: Please note that there can be some variations depending on the specific keyboard model.

Keycap Dimensions Chart by Profile

When choosing keycaps, the "profile" refers to the 3D shape of each key and how they all fit together on your keyboard. This shape affects how comfortable the keys feel when you type (and even the sound they make – bigger keys often sound deeper and more hollow). But the good news is, most keycap profiles work with most keyboards. Here's an exploration of some popular keycap profiles:

Profile	Description	Type of Keys	Dimensions
OEM	The standard, widely available keycap design with angled tops 11.9 mm height	Standard Alphanumeric	1u
		Backspace/Enter	2u
		Shift (Left & Right)	1.25u or 1.75u
		Ctrl, Alt, Fn	1.25u
		Modifier Keys (Caps Lock, Tab, Delete)	1.75u
		Function Keys (F1-F12)	1u
		Spacebar	6.25u
Cherry	Similar to OEM but shorter, offering a popular alternative 9.4 mm height	Standard Alphanumeric	1u
		Backspace/Enter	2u
		Shift (Left & Right)	1.25u or 1.75u
		Ctrl, Alt, Fn	1.25u
		Modifier Keys (Caps Lock, Tab, Delete)	1.75u
		Function Keys (F1-F12)	1u
		Spacebar	6.25u
DSA	Lower profile with a completely round top for a different typing experience. 7.6 mm tall	Standard Alphanumeric	1u
		Backspace/Enter	2u
		Shift (Left & Right)	1.25u or 1.75u
		Ctrl, Alt, Fn	1.25u
		Modifier Keys (Caps Lock, Tab, Delete)	1.75u
		Function Keys (F1-F12)	1u
		Spacebar	6.25u
SA	Tallest profile with a slightly rounded and angled top for a vintage aesthetic. 16.5 mm height	Standard Alphanumeric	1u
		Backspace/Enter	2u
		Shift (Left & Right)	1.25u or 1.75u
		Ctrl, Alt, Fn	1.25u
		Modifier Keys (Caps Lock, Tab, Delete)	1.75u
		Function Keys (F1-F12)	1u
		Spacebar	6.25u
XDA	Medium height with a spherical top, offering a balance between comfort and sculpted profiles. 9.1 mm height	Standard Alphanumeric	1u
		Backspace/Enter	2u
		Shift (Left & Right)	1.25u or 1.75u
		Ctrl, Alt, Fn	1.25u
		Modifier Keys (Caps Lock, Tab, Delete)	1.75u
		Function Keys (F1-F12)	1u
		Spacebar	6.25u

While the keycap profiles OEM, Cherry, DSA, SA, XDA offer distinct typing experience due to their height and top curvature, it's important to remember that within a specific key type (like standard alphanumeric keys), the size in units (typically 1u) remains consistent across most profiles. This allows for greater interchangeability when choosing keycaps, as long as the overall layout (full-size, tenkeyless, etc.) is compatible

By understanding these profiles’ keycap dimensions, you can embark on a personalized journey to create the perfect typing experience and a keyboard that reflects your unique style!

Keycap Dimension Measurement Tools

To ensure a perfect fit for your keycaps, you need to have the essential tools and knowledge to accurately measure your keycap dimensions and explore compatible replacements, unlocking a world of personalized comfort and customized style for your mechanical keyboard.

Keyboard Layout Editor

In a user-friendly online environment, this online tool empowers you to visualize keyboard layouts and experiment with different keycap sizes. Drag and drop virtual keycaps to create custom layouts and see how various keycap sizes would look. Keyboard layout editor is a fantastic way to plan your dream keyboard and ensure compatibility with different keycap sets before you commit.

Keycaps.info

Keycaps.info is a comprehensive resource website that serves as a treasure trove of information on keycap profiles and their corresponding dimensions. Enthusiasts seeking in-depth specifications will find this website particularly valuable.

The website provides reference dimensions for various keycap profiles, allowing you to make informed choices when selecting compatible keycap sets for your specific keyboard. While a basic understanding of keycap profiles might be helpful for navigating the website, the overall difficulty in using Keycaps.info is low to moderate.

Ruler

A ruler is a classic measuring tool that comes in handy for determining the width and length of a keycap which is perfect for beginners or those who need to take basic measurements. Simply place the ruler along the flat edge of the keycap and note down the measurement in millimeters. This method is sufficient for most situations, as keycap compatibility is often determined by the width and length of the keycap base, especially for keycaps with uniform profiles.

Protractor

A protractor helps measure curvature on sculpted keycaps, affecting typing feel and compatibility. It is suitable for enthusiasts who want precise measurements for sculpted profiles. Moreover, this method is useful for measuring curvature, especially on SA or DSA profiles.

Other measuring tools

You can use other measuring tools such as: calipers and micrometers. They are precision measuring instruments that offer the highest level of accuracy for measuring keycap dimensions in millimeters. These tools are ideal for experienced users and professionals who require highly accurate measurements down to the smallest fraction of a millimeter. 

Here're some tips for you to measure keycap dimensions correctly:

• Identify your keycap profile: Knowing the profile helps you locate specific reference dimensions.
• Measure flat surfaces for accurate results: Avoid measuring curved sections unless using a protractor.
• Calipers and micrometers require steady hands and practice: Ensure proper calibration and technique for precise measurements.
• Divide the width and height of the keycap by 19.05: If you are measuring a keycap that is 19.05mm wide and 19.05mm tall. The keycap size in "U" units would be: width / 19.05 = 1 U and height / 19.05 = 1 U. Therefore, this keycap is 1U x 1U in size.

How to Choose the Right Keycap Dimensions?

Choosing the right keycap dimensions involves several factors:

• Match keyboard layout: Ensure keycap sizes and spacing align with your specific keyboard's layout (ANSI, ISO, JIS). Mismatched keycaps can affect functionality.
• Hand and finger size: Consider your hand and finger size for optimal comfort. Larger keys might suit bigger hands, while smaller keys might be better for those with smaller fingers.
• Prioritize comfort and ergonomics: Prioritize keycap height, angle, and curvature that promote a natural hand and wrist position while typing.
• Watch typing tests and reviews: Explore typing test videos and reviews to understand how different keycap sizes and profiles feel during use.
• Seek advice from community and expert advice: If unsure, seek guidance from online keyboard communities or experts who can offer valuable insights based on their experiences. 

Related Article: Are All Keycaps The Same Size?

In conclusion, this comprehensive guide has equipped you with the knowledge to navigate keycap dimensions and how to measure them correctly. Remember, the perfect keycap choice is ultimately a personal journey. Experiment with different profiles, consider your typing style, and prioritize the features most important to you.

FAQs

How long is a 1u keycap?

A 1u keycap typically measures around 19.05 millimeters in width.

Are keycaps one size?

No. Keycaps come in various sizes (multiples of 1u) to accommodate different key positions on the keyboard.

What is the height of keycaps?

Keycap height varies depending on the profile (sculpted or uniform). Refer to the specific keycap profile information for height details.

How wide is a keycap in inches?

While some resources might use inches, millimeters (mm) are the standard unit for measuring keycaps. Convert millimeters to inches using a conversion chart if needed.

How thick is a keycap?

Similar to height, keycap thickness depends on the profile.