Tips for Making Smaller PowerPoint Files

PowerPoint presentations are a valuable tool for educating the public about invasive plants. The files can be downloaded and used by educators in group settings or simply viewed by people wanting a better understanding of invasive plants. Photos and graphics enhance the presentations, reinforcing the message of the presentation.

In order to use PowerPoint presentations on the web, it is important to minimize the file size to decrease the download time and save space on the server. There are two aspects to accomplishing this: minimizing image size and bypassing the template features.

Short Version

  • Use image editing software to reduce the resolution of the image to 96 dpi or less.
  • Use image editing software to reduce the size of the image. For a full screen image in PowerPoint, the image should be no more than 6 inches high by 9 inches wide.
  • Do not adjust the size of an image within PowerPoint (small adjustments OK). The original size remains in memory.
  • Avoid the use of PowerPoint design templates.


More Explanation:

Minimizing image files:

Generally, photos are digitized at a resolution of 300 dpi (dots per inch) or more. The newer digital cameras frequently create huge image sizes due to their high resolutions. This is great for print media, but images intended to be viewed onscreen should be no more than 96 dpi (72 dpi is a common default size). The eye cannot perceive resolutions greater than 96 when viewed onscreen. Many graphics designed for printing are also very large files and need to be reduced.

The file size of your PowerPoint presentation can be roughly estimated by adding up the file sizes of the images in the presentation. If you have 20 images that are about 100 KB in size, your file size will be at least 2 MB. If those same 20 image are 800 KB, the file size is at least 16 MB!

The usual file formats for the web are JPEG (or JPG) and GIF. Do not use bitmaps (BMP) since they cannot be viewed from a browser without special software. TIFF format are usually (but not always) too large. JPG is best for images with many colors. GIFs are used for fewer colors or when a transparent background is needed. Do not create too many incremental copies if your file is JPEG. Each time you copy a JPEG, resolution is lost and it starts to look fuzzy. This is called the lossy effect. GIF files are lossless and do not lose resolution

In order to change the size of an image, you need to have some sort of image editing software. Common choices are: Adobe PhotoShop, Macromedia Fireworks, Kodak Imaging, or other software bundled with cameras and scanners. Follow the instructions included with your software for Resizing. Always save your original image and create a copy when resizing. Sometimes changing the resolution is a separate operation from changing the image size. In these situations, when you reduce the resolution without changing the image size, the program compensates by increasing the size of the image. Suddenly, your 4x6 image is 22x30 inches. You must go back in and reduce the file size to about 6 x 9 inches for a full PowerPoint page.

Note: Simply resizing a photo from within PowerPoint does not change the file size. In fact, the file will be larger because PowerPoint keeps track of the original image size in case you want to go back to the original.

Bypass Template Features:

Microsoft attempts to make its software easy to use. In PowerPoint, there are several slide templates to make creating the presentation less time-consuming. However, there is a price paid in file size if you use these templates.

Use Design Templates with caution. A PowerPoint (Office 2000 version) file with one blank slide is 8 KB. The same blank slide with the Strategic Design Template is 156 KB! Multiply that by the number of slides in your presentations. This difference varies depending on the template used. Using the Soaring template, the file is 22 KB.

Make sure you save the file under the correct version of PowerPoint. Saving under a previous version can increase the file size geometrically. For instance, the Strategic Design Template file from above, saved as a previous version, is 2,396 KB!

In some versions of PowerPoint, the file size increases with the use of the layout templates (those are the ones with text boxes and image placeholders already arranged for you). Do not use these unless your slide exactly matches the template. Use a blank slide instead.