In the “old days,” computer monitors and televisions all had a 4:3 aspect ratio.

What does that mean in English?

It means that the ratio of width to height is 4 to 3.

So an old monitor might have been 24-inches wide by eighteen inches tall. Four times six = 24 and three times six = 18.

Usually, screens are measured by the number of dots rather than by the number of images. The number of inches in a 27-inch monitor actually describes an approximate diagonal measurement.

An old 4:3 monitor might have had a resolution of 640 x 480 pixels.

Since about 2009, the new “widescreen” format has become standard. That's 16:9 instead of 4:3.

In pixel terms, a 1080p “HD” monitor has 1920 x 1080 pixels. That's a lot more dots that the old screes have.

A 4K monitor is double the resolution in each direction. Tha's 3840 x 2160

Ouch! All this math! How does it affect our slide presentations?

First, if you're still using 4:3 slides, if you show them on a remotely recent projector or monitor, they'll have a black bar on either side. They're just not wide enough to fill the screen.

Second, once you have the ratio down, you'll want to create backgrounds and other graphics at higher resolution. In your design software, create a 1920 x 1080 pixel work area to design in.

If you hire a designer to create your slides, they'll probably do this automatically but it's worth specifying that you want your slides to be 16:9 and 1080p.

Use the available space and fill the screen with your beautiful images and big ideas.