Keycap Dimensions | A Comprehensive Guide for Beginners

By Dat Thanh on Jul 04, 2024

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: 

Unit is used to measure keycap instead of sizing keycap dimensions in inches and keycap dimensions in cm | source: matt3o
Unit is used to measure keycap instead of sizing keycap dimensions in inches and keycap dimensions in cm | source: matt3o

 

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.

Measuring keycap dimensions of the ansi layout | source: intercom
Measuring keycap dimensions of the ansi layout | source: intercom
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.

Measuring keycap dimensions of the iso layout | source: keychron
Measuring keycap dimensions of the iso layout | source: keychron
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.

Measuring keycap dimensions of the jis layout | source: keychron
Measuring keycap dimensions of the jis layout | source: keychron
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:

Keycap dimensions between various profiles
Keycap dimensions between various profiles

Profile Description Type of Keys Dimensions
OEM

 

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

 

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

 

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

 

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

 

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

Keyboard layout editor is useful for cherry mx keycap dimensions | source: keyboard layout editor
Keyboard layout editor is useful for cherry mx keycap dimensions | source: 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

You can easily find oem keycap dimensions in here | source: keycaps. Info
You can easily find oem keycap dimensions in here | source: 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

Measuring keycap dimensions by ruler is such a classic way | source: instructable
Measuring keycap dimensions by ruler is such a classic way | source: instructable

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

You can use protractor to measure not only sa keycap dimensions but also other keycap profiles | source: amazon 
You can use protractor to measure not only sa keycap dimensions but also other keycap profiles | source: amazon

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

Calipers and micrometers are highly accurate keycap dimensions measurements | source: machinist guides
Calipers and micrometers are highly accurate keycap dimensions measurements | source: machinist guides

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?

Please consider several factors to choose the right keycap dimensions | source: tomshardware
Please consider several factors to choose the right keycap dimensions | source: tomshardware

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.

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