## How many pixels is a centimeter?

What are digital measurement units? What do they mean? How to convert them? We will try to answer these seemingly difficult questions in a simple way.

To start with, digital units of measurement are relative – they mean different lengths depending on various factors. Such factors can be, for example, the resolution, the set parameters or the dimensions of the element.

## Types of digital units of measurement

The digital units of measurement are:

- pixel
- point
- cal
- cm
- firet
- percent
- em and their derivatives.

## Digital Units of Measure – Pixel

The basic digital unit of measurement is the pixel. It is the smallest element of a digital image and it is used to express the screen resolution or dimensions of a digital image. It is often confused with a point, which is understandable, because at standard definition they express the same length.

## Digital Units of Measure – Point

The point is often used to express the degree of handwriting, or colloquially speaking, „font size”. It is a unit derived from an inch, it expresses the length exactly 72 times smaller. Another derivative of an inch that you may come across in design is the pica, which is ⅙ of an inch, or 12 points. Pica is a relative unit that depends on the resolution. The resolution we are talking about in this case is the raster resolution. We clarify it, because it is not about the screen resolution expressed in lines (e.g. 720p) or pixels (e.g. 1920×1200), nor about the print resolution, which is also expressed in ppi or dpi.

## Digital Units of Measure – Firet

Another digital unit of measurement related to design is firet. You’ve probably never heard of him, he’s a smart little guy who hides in advanced typography. It is not less, not more, exactly the same as the set degree of writing. 1 firet has, for example, a pause or an em space. At 72 points, the pause will be 1 inch.

## Digital Units of Measure – Percent

Units that we are going to discuss now are not exactly units, because they actually express multiples and are more of a mathematical operation. The only such unit that is used not only in programming is the percentage. It’s easy – the percentage is for a hundredth of an element. In design, we use percent only when we want to change the dimension of an element; in programming, the percentage refers to the parent of a given element.

Percentage derivatives are vh (view height) and vw (view width) units. 1 vh is 1% of the height of the screen, and 1 vw is 1% of its width.

## Digital Units of Measure – Em i Rem

There are two more digital units used in programming: em (element) and rem (root element). Em is a multiple of the element’s parent dimension and rem is a multiple of the base element (which can only be one per page).

## Converting digital units of measurement – example

For display: At 1920×1200 screen resolution and standard raster resolution, if the base element has 1 pixel, the parent element of the variable X 10 pixels, and the variable X 100 pixels, then the variable x will have 100 rem, 10 em, 1920 vw, 1200 vh, 1000 %, 100 dots, ~ 1.4 inches, and ~ 3.5 cm.

## So after all, how many pixels is a centimeter?

To answer the first question: a centimeter will have a different number of pixels depending on the resolution 🙂 The standard resolution is 72 ppi, so 72 pixels are 1 inch, or 2.54 cm. So the calculations show that one centimeter is usually just over 28 pixels.