How to Change Slide Size in PowerPoint to A3

To change a PowerPoint presentation to A3, open the Design tab, choose Slide Size > Custom Slide Size, and set the slide dimensions to 42 × 29.7 cm for landscape or 29.7 × 42 cm for portrait. Choose how to scale existing content when prompted, then check the slides and print settings. A3 changes the size of every slide in the presentation; it does not automatically make a printer use A3 paper.

What You’ll Need

PowerPoint for Microsoft 365 on Windows, or PowerPoint for Mac. The steps below use the Windows ribbon.
The presentation you want to resize. Save a copy first if you want to keep the original slide size and layout unchanged.
The intended orientation: landscape or portrait. A3 is 42 cm wide by 29.7 cm high in landscape, and 29.7 cm wide by 42 cm high in portrait.
If you plan to print, access to an A3-capable printer or a print service that accepts A3 files. Check whether the printer supports borderless printing if artwork must reach the paper edge.

Step-by-Step

Open the presentation and save a working copy. Open the file in PowerPoint. Choose File > Save As (or File > Save a Copy, depending on the interface) and give the copy a new name if you need to preserve the original. Resizing affects the slide dimensions throughout the presentation, so keeping a copy makes it easy to compare or revert without rebuilding the previous layout.
Open the slide-size controls. Select the Design tab on the ribbon. In the Customize group, choose Slide Size, then select Custom Slide Size. If the ribbon is narrow, the controls may be grouped or represented by a compact menu; expand the Design ribbon or look for the Slide Size menu. Do not use a zoom control: zoom changes how large the slide looks on screen, not the slide dimensions.
Choose A3 from the paper-size list if it is available. In the Slide Size dialog, open Slides sized for and look for an A3 option. Selecting it should fill in the A3 dimensions. Depending on your PowerPoint version and regional settings, the list may use a label such as A3 Paper or may not include A3 at all. Check the width and height rather than relying only on the label.
Enter the dimensions manually if needed. Set Width to 42 cm and Height to 29.7 cm for landscape. For portrait, enter 29.7 cm for Width and 42 cm for Height. If PowerPoint displays inches, use approximately 16.54 in by 11.69 in for landscape, or reverse those values for portrait. A3 is 297 × 420 mm; small rounding differences in the displayed values are normal.
Set the slide orientation. In the same dialog, select Landscape or Portrait under Orientation for slides. Make sure this agrees with the dimensions you entered. For example, a 42 cm width and 29.7 cm height is landscape. The notes, handouts, or outline orientation setting is separate; change it only if you also want those printed pages to use a different orientation.
Apply the new size. Click OK. PowerPoint may ask how to scale the content on your slides. Choose Ensure Fit to scale content down or keep it within the new slide boundaries, or choose Maximize to use more of the available slide area. The exact prompt can vary by version. Neither choice redesigns the presentation, so inspect slides afterward, especially if you are changing from widescreen 16:9 to A3 proportions.
Review the presentation slide by slide. Look for text that has become too small, objects that overlap, images or shapes that sit outside the slide, and charts or tables that no longer fit comfortably. Use View > Slide Sorter for a quick overview, then open any crowded slides individually. Check title positions, margins, footers, and any objects aligned to the old slide edge.
Make any necessary layout adjustments. Move or resize objects, adjust text-box dimensions, and reposition images to suit the new format. If the original design was widescreen, consider rearranging content into columns or using the extra page area for larger visuals rather than stretching every object. Save the file after checking the changes.
Confirm the print output separately. Choose File > Print and check the paper-size setting in PowerPoint and, if available, the printer properties. Set the printer paper to A3 and preview the output. If you are sending the deck to a print shop, export a PDF and confirm that its page size is A3 before sharing it.

Common Mistakes

Changing zoom instead of slide size: The zoom percentage near the bottom of the PowerPoint window affects only the on-screen view. It does not change the dimensions of the slides or the page size in a printed file. Use the Slide Size controls on the Design tab.

Entering landscape dimensions in the wrong order: A3 landscape is wider than it is tall: 42 × 29.7 cm. If you enter 29.7 × 42 cm, you have set portrait dimensions. Check both the width and height fields before clicking OK.

Expecting every object to resize perfectly: Scaling can keep objects inside the slide, but it cannot make a crowded design readable or choose a new layout for you. Fonts, images, grouped objects, and elements near the edge may need manual adjustment.

Assuming A3 slides guarantee A3 printing: Slide dimensions and printer paper settings are separate. A standard printer may print the A3 slide reduced to fit smaller paper, crop it, or reject the job. Confirm the paper size in the print dialog and printer settings.

Ignoring the scaling prompt: Ensure Fit and Maximize can produce different results. If you click through without checking the preview, content may appear smaller than expected or may extend beyond the slide. Choose deliberately, then review the deck.

Tips

Use the same units throughout the sizing dialog. PowerPoint generally accepts a unit suffix such as cm or in when you type a measurement, but confirm the displayed result after pressing Enter.
For a presentation that will be projected as well as printed, check it at presentation size. A3 provides a large physical page, but text that was designed for a widescreen display may still be too small when viewed from a distance.
Keep important text, logos, and page numbers away from the extreme edge. Many printers have a non-printable margin, even when the document itself is correctly set to A3.
For edge-to-edge graphics, ask the printer about bleed and trim requirements. PowerPoint’s slide size sets the page dimensions, but does not by itself add print-shop bleed or crop marks.
If only one slide needs to be A3, consider making a separate presentation for it. PowerPoint applies the slide size to the whole presentation rather than to an individual slide.
After resizing, save and reopen the file or export a PDF to check that the chosen dimensions remain intact. A PDF is often more predictable for printing because its page size can be checked before the file goes to a printer.

Troubleshooting

A3 is missing from the size list: Choose Custom Slide Size and enter 42 × 29.7 cm or 29.7 × 42 cm manually. If the fields display inches, enter the equivalent values of about 16.54 × 11.69 inches. The A3 standard is 297 × 420 mm, so check the orientation as well as the numbers.

The slides look cropped or elements are cut off: Reopen Design > Slide Size > Custom Slide Size and verify the width, height, and orientation. Then inspect objects near slide edges. If the problem began after selecting Maximize, undo the change immediately with Ctrl+Z on Windows (or Command+Z on Mac), reopen the sizing dialog, and try Ensure Fit. If the change has already been saved or more edits have followed, use the saved original copy and resize again.

Text or images look too small: This is common when a presentation changes from widescreen proportions or when Ensure Fit scales a layout to keep all content inside the slide. Increase text sizes where appropriate, enlarge or reposition key images, and reflow content instead of stretching it. Check the entire deck because slide layouts can differ.

The file is A3, but the printout is not: In File > Print, choose an A3 paper option if the printer offers one. Open printer properties to confirm the loaded paper size and orientation. If A3 is unavailable, select a printer or print service that supports it; changing the PowerPoint slide size cannot add a paper size that the device does not support.

The menu path looks different on a Mac: In PowerPoint for Mac, select Design > Slide Size > Page Setup or Custom Slide Size, depending on the version. Enter the same A3 width and height and choose the orientation. The dialog layout and the wording of the content-scaling choices may differ from Windows, so verify the dimensions and review the slides after applying them.

Frequently Asked Questions

What are the exact dimensions of an A3 PowerPoint slide?
A3 is 297 × 420 mm, or 29.7 × 42 cm. Use 42 cm wide by 29.7 cm high for landscape, and 29.7 cm wide by 42 cm high for portrait. PowerPoint may show rounded inch equivalents of approximately 16.54 and 11.69 inches.

Can I change just one slide to A3?
No. PowerPoint’s Slide Size setting applies to the entire presentation, not a single slide. If you need one A3 page alongside slides of another size, create a separate presentation for that page or export and combine pages using a suitable document or print workflow.

Will changing the slide size distort my content?
PowerPoint’s scaling choices generally resize objects while preserving their proportions, but the layout may still look different. Text may become smaller, objects may shift relative to the slide, and content can be cropped if it no longer fits. Review and adjust each slide rather than assuming the resize is finished once the dialog closes.

Should I choose Ensure Fit or Maximize?
Choose Ensure Fit when keeping existing content within the slide is the priority; it may leave more empty space or make elements smaller. Choose Maximize when using more of the new slide area matters, but inspect carefully for objects that extend beyond the edges. The best choice depends on the old aspect ratio and layout, so you can undo and try the other option if needed.

Does setting the slide to A3 make my printer print on A3 paper?
No. The slide size defines the presentation page, while paper size is selected in the print dialog and printer properties. Choose A3 there too, and check the print preview. If your printer only supports smaller paper, the output may be scaled or cropped.

Can I change an A3 presentation back to widescreen?
Yes. Open Design > Slide Size > Widescreen or choose Custom Slide Size and enter the desired dimensions. PowerPoint may again ask how to scale the content. Use a saved copy or undo if the new layout is not suitable, then check all slides after switching back.

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