How to Change the Slide Size in PowerPoint (16:9, 4:3, A4 and Custom)
New presentations are widescreen (16:9), which suits every modern screen. But an old projector might be 4:3, a printed handout might want A4, and a social media post wants a square. Changing the size is easy; the trick is choosing how PowerPoint rescales what's already on the slides.
Quick reference
| What you want | How |
|---|---|
| Switch between 16:9 and 4:3 | Design → Slide Size |
| Anything else | Design → Slide Size → Custom Slide Size |
| Fill the new size (may crop) | Maximize |
| Shrink everything to fit | Ensure Fit |
| Portrait slides | Custom Slide Size → Orientation → Portrait |
1. Switch between widescreen and standard
Design → Slide Size and choose Standard (4:3) or Widescreen (16:9). If the presentation already has content, PowerPoint asks how to scale it:
• Maximize — keeps the content as big as possible. Going from 16:9 to 4:3, things may run off the sides.
• Ensure Fit — shrinks everything so it all stays on the slide. Safer.
• Ensure Fit — shrinks everything so it all stays on the slide. Safer.
Check every slide afterwards whichever you choose.
2. Set a custom size
Design → Slide Size → Custom Slide Size opens a dialog with:
• Slides sized for — presets including A4 Paper, Letter Paper, Overhead, Banner and 16:10.
• Width and Height — type any size in centimetres.
• Orientation — Portrait or Landscape for slides, and separately for notes and handouts.
• Width and Height — type any size in centimetres.
• Orientation — Portrait or Landscape for slides, and separately for notes and handouts.
Useful sizes:
| Use | Size |
|---|---|
| A4 document, portrait | 21 × 29.7 cm |
| Instagram square | 20 × 20 cm (any square) |
| Instagram portrait post | 20 × 25 cm (4:5) |
| A1 poster | 59.4 × 84.1 cm |
3. Change the size before you build
If you know a deck needs an unusual size, set it first. Resizing afterwards is where things go wrong — text boxes that no longer fit, pictures stretched, backgrounds misaligned.
4. Fix slides after resizing
• Home → Reset snaps placeholders back to the layout for the new size.
• Pictures that look stretched: Picture Format → Reset Picture ▾ → Reset Picture & Size, then resize from a corner.
• Background pictures set in Format Background stretch to the new shape — replace them with ones in the right proportion.
• Pictures that look stretched: Picture Format → Reset Picture ▾ → Reset Picture & Size, then resize from a corner.
• Background pictures set in Format Background stretch to the new shape — replace them with ones in the right proportion.
5. Mixed sizes
A presentation has one slide size. You can't have a portrait slide in a landscape deck. If you need both, link to a second file, or put a portrait image on a landscape slide with a plain background.
Troubleshooting
Everything looks squashed after switching to 4:3. You chose Maximize. Undo (Ctrl + Z) and choose Ensure Fit.
The slide size dialog shows inches. It follows your Windows regional settings. Type cm after the number and PowerPoint converts it.
My printed slides have white borders. Slides are 16:9 and paper isn't. Choose A4 Paper as the slide size, or tick Scale to Fit Paper in the print settings.
Wrapping up
Design → Slide Size for 16:9 and 4:3, Custom Slide Size for anything else. Choose Ensure Fit when converting existing slides, and set unusual sizes before you start building.
