Buying a mechanical keyboard can seem like a daunting task. Size, switch type, case material, keycaps, and more, all need to be considered. However, once you decide on a keyboard size, the choices narrow down considerably.
Size is determined by the number of keys, and in this guide, we'll talk about the most common sizes a beginner should consider, starting from the largest to the smallest. Though by no means comprehensive, this guide should get you started on getting a keyboard that's an upgrade over your laptop or standard workstation keyboard.
104-key (Full size keyboard)
The 104-key keyboard was commonly used with desktop computers before laptops became the norm. All the keys you need are found here, most importantly, the numeric keypad for data entry. Its main downside is the large physical size, which takes up a lot more space on your desk, and may require you to use your mouse (for right-handers) further away than is comfortable for your shoulders.
Can Buy: If you need the numeric keypad
Check out our review of the Logitech MX Mechanical Keyboard

87-key (Tenkeyless or TKL)
As its name suggests, the Tenkeyless keyboard removes the numeric keypad. It is otherwise identical to the 104-key keyboard. This saves you desktop space, and solves the problem of the mouse being placed too far. It is the most practical option for the majority of users, and is a popular layout offered by many brands, so there are choices aplenty.
Can Buy: If you need everything in a full-size keyboard except the numpad
Check out our review of the Keychron K8 Wireless Mechanical Keyboard

75% keyboard
The 75% keyboard layout, with 84 keys (+/- one or two depending on brand), looks very similar to what you find on a mainstream or business laptop. The biggest difference from your notebook is the additional column of keys on the right (usually PgUp, PgDn, Home, End). Think of this size as being a smaller TKL keyboard with its right-side section pushed closer to the middle to save even more space. This layout is becoming increasingly popular so finding one won't be hard.
Can Buy: If you want a keyboard that's compact, and similar to your laptop experience
Check out our review of the Iqunix L80 Mechanical Keyboard

65% keyboard
Remove the function keys on a 75% keyboard, and you get a 65% keyboard. This size makes sense for those that want something even more compact, and seldom use the F1 to F12 keys. This function row is still available, usually by holding Fn and the corresponding number key (e.g Fn+1 for F1). Take note that there is no dedicated tilde (~) key, which may be important to some MacOS users who use the cmd+~ shortcut to switch between application windows.
Can Buy: If you want something really compact, and don't need the function row
Check out our review of the Keychron K7 Ultra-slim Wireless Keyboard

Don't go smaller or weirder
There are other sizes and layouts like the even smaller 60%, 40%, ergonomic split keyboards, and so on. If you are buying your first mechanical keyboard, just ignore them for now. The four sizes we've featured here will more than likely fulfill your needs without sacrificing too much functionality.