Difference Between Pixel (Px) and Point (Pt) Font Sizes in Email Signatures

What is a Pixel (px)?

A pixel (px) at 96DPI (dots per inch) is equal to 0.2645835‬ millimeters, 0.010416675‬ inches, or 0.75 point. It is a measurement of how tall a font is in pixels which are visible on your computer screen. So, if a font is 12 pixels in height, that means it takes up 12 pixels on your screen from the top of the letter, to the bottom, which also includes the characters that have sections which are under the guide line, such as a “p” character.

Pixel’s are the preferred method to calculate font sizes in email signatures, because they need to be measured on LCD screens, rather than physically. Since computer and mobile devices all have LCD screens, it makes sense to use pixels as a unit of measurement.

What is a Point (pt)?

A point (pt) is equal to 0.352778 millimeters, 0.0138889 inches, or 1.333 pixels. Because millimeters and inches are measurements of physical items, they are not ideal to use with computer or mobile based applications because they dont always represent the correct size because of differences in screen resolution.

Some email clients, such as Outlook still use a point as a font size measurement when it comes to email signatures. This is rather annoying because most HTML email signatures are created using pixels for font sizes, because that is the web standard.

Why the difference between pixels and points for fonts?

Units to measure the size of fonts have changed dramatically over time. Points used to be the major (and only) way of measuring the size of a font on written paper since it was first established in the 1500’s.

Computer (and mobile device) screens are made up of many tiny little LED’s which in software terminology are referred to as pixels. Some monitors have more of them, and some have less. This means that the measurement of “points” was no longer appropriate since 1 point was tied to 0.352 millimeters, and physical units of measurement dont work on computers screens.

Since personal computers made their first appearance in the early 80’s, we’ve since found a newer and more fitting way to measure font sizes, since monitor resolutions varied greatly. The digital way to measure font sizes is in pixels.

Some word processors such as Microsoft Word still use points as units of measurement for fonts. This is because some of the time, the documents are printed and converted to physical documents, so it makes sense to use points. However, it doesn’t make sense to use points as a unit of measurement for email applications such as Microsoft Outlook, because…well…it’s email, AKA electronic mail, but to this day it’s still used.

Luckily, there is a standard conversion between points and pixels which makes life easier.

Our Recommendation

We make email signatures for a living, so we’re experienced when it comes to email signature font sizes and the best way to measure them. If you’re creating an email signature and you’re not sure if you should use points or pixels, our recommendation is that you always use pixel as a form of font measurement for email signatures, especially if they are created in HTML. This will ensure maximum compatibility between various email clients which means your signature will always have the correct font sizes.

Looking to create an email signature from scratch? Why not try our free email signature generator which can help you with the whole process from start to finish.