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In Canva, change the measurement unit while creating a custom-size design: go to Create a design → Custom size, choose cm or mm from the unit menu, enter the width and height, then select Create new design.
For an existing design, open Resize or Resize & Magic Switch, choose Custom size, select the unit, and decide whether to resize the current design or create a copy.
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What “size metric” means in Canva
“Size metric” usually means the unit Canva uses for a design’s width and height. Canva’s custom-size workflow supports inches (in), millimeters (mm), centimeters (cm), and pixels (px).
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These units apply to the design canvas. They are not the same as changing an image inside the design, changing the editor’s zoom, or changing an exported file’s resolution.
- cm: useful for general print projects such as posters, cards, flyers, labels, and worksheets.
- mm: useful for precise print dimensions, trim sizes, and bleed specifications.
- in: common for US print specifications.
- px: generally best for websites, apps, social media, and other screen-based graphics.
Change to centimeters or millimeters before creating a design
- Open Canva.
- Select Create a design.
- Choose Custom size.
- Find the unit selector beside or below the width and height fields.
- Choose cm or mm.
- Enter the required width and height.
- Select Create new design.
For example, a 10 × 15 cm card uses Width: 10, Height: 15, and Unit: cm. The same dimensions in millimeters are 100 × 150 mm.
On iOS and Android, the labels and menu locations can differ from the desktop interface. Open the custom-size design option and look for the unit menu next to the dimension fields.
Canva identifies inches, millimeters, centimeters, and pixels as options in its custom-size workflow: Canva’s resize information.
Change the unit of an existing Canva design
- Open the design.
- Select Resize & Magic Switch in the editor toolbar. Depending on your account, design type, language, or editor version, the control may be labeled Resize or Magic Resize.
- Choose Resize.
- Select Custom size.
- Choose cm or mm.
- Enter the new width and height.
- Choose either Copy and resize or Resize.
Copy and resize preserves the original and creates a separate version. It is the safer choice, especially when changing from portrait to landscape or changing the aspect ratio. Resize changes the current design.
Canva’s documented workflow describes both options, but availability can vary by account type and design format. Check Canva’s current help instructions for resizing and changing page orientation.
Changing cm to mm without changing the physical size
Changing the unit alone does not make a design larger, smaller, sharper, or lower quality. You must convert the numbers correctly:
- 1 inch = 2.54 cm
- 1 inch = 25.4 mm
- 1 cm = 10 mm
Therefore, 10 cm equals 100 mm. If you enter 10 mm instead of 100 mm, the resulting design is one-tenth as wide.
For print, physical dimensions and image resolution are related but different. At 300 PPI, 1 inch is 300 pixels, 1 cm is approximately 118.11 pixels, and 1 mm is approximately 11.81 pixels. These are resolution-based examples, not a Canva requirement. A correctly sized canvas can still contain low-resolution images.
Which unit should you choose?
| Unit | Best for | Example |
|---|---|---|
| cm | General print dimensions | A4 page: 21 × 29.7 cm |
| mm | Precise print, trim, or bleed measurements | Card: 100 × 150 mm |
| in | US print specifications | Use the dimensions supplied by the printer |
| px | Digital graphics and screen layouts | 1920 × 1080 px graphic |
Use the unit specified by your printer, client, publication, or destination platform. For more context on ISO paper sizes and North American formats, see Canva’s paper-size guide.
If you meant an image rather than the whole design
Changing the canvas size affects the entire page. To resize an individual image:
- Select the image.
- Drag a corner handle to scale it.
- Double-click the image or choose Crop to change which part is visible.
If you need to create a separate image at custom dimensions, use Canva’s Image Resizer. It lets you upload an image, choose a preset or custom size, adjust it in the editor, and download it as a JPG or PNG.
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The control may be missing because you are in a template-selection flow, using a design type that does not support resizing, working in Canva Docs, or using an account without access to the relevant resize feature. Canva’s interface labels also change over time.
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Try this recovery path:
- Return to Canva’s home page.
- Select Create a design and search for Custom size.
- For an existing design, inspect the top toolbar for Resize, Resize & Magic Switch, or Magic Resize.
- If the control is still unavailable, create a new custom-size design and copy the original elements into it.
Canva’s plan comparison associates some resize and Magic Resize features with paid plans, but creating a new custom-size design, resizing an existing design, and adapting a design to multiple formats may have different availability. Check the current Canva pricing and plan details rather than assuming that every resize action is free or paid. Canva Docs may not support the same resize workflow as regular designs.
Why did the layout change after resizing?
Changing the dimensions can change the canvas ratio. Canva attempts to adapt the layout, but text may reflow, images may crop differently, margins may shift, and elements may move. This is especially likely when converting a square design to a wide banner or a portrait page to landscape.
Use Copy and resize first, then check text wrapping, image crops, spacing, alignment, and margins. Treat a major orientation change as a starting point for a redesign, not as a guaranteed perfect conversion. Canva describes this automated adaptation through its Magic Resize and Magic Switch tools.
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- Confirm the printer’s required width, height, trim size, and unit.
- Ask whether bleed is required and use the printer’s specified amount; do not add it arbitrarily.
- Use the export format requested, such as a print-ready PDF if required.
- Check whether crop marks or CMYK are required.
- Review the exported file at 100% scale where possible.
- Confirm that placed images have sufficient resolution for the final physical size.
Choosing cm or mm helps specify the canvas dimensions, but the unit selector alone cannot guarantee accurate printing. Export settings, source-image resolution, printer settings, paper handling, and the printer’s production requirements also matter.
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