You can use your web browser to see the exact dimensions of the image spaces on your site.

Most modern browsers have an option called "Inspect Element" which is accessible by right-clicking over an area of a website. When selecting this option, typically a panel comes up showing the HTML content and the dimensions of the area.

Hover your mouse over an image in the web page > Right Click / Control Click > Inspect Element

In the new window that appears in the bottom of your browser, move your mouse within the code until you see the content area highlighted (usually in blue).

You’ll notice a tooltip near the highlighting. The first number is the width.