How to Calculate Canvas Size

Choosing the right canvas size sounds simple until you actually have to do it. Too small and the work feels cramped. Too large and you’re fighting empty space or wasting materials. Whether you’re painting for an exhibition, a commission, or your own studio practice, calculating canvas size is about planning, not guesswork.

Here’s how to approach it in a way that makes sense.

1. Start With the Purpose

Before you touch a ruler, ask why the painting exists. Is it meant to hang in a specific space? Is it for a series? Is it a study or a finished piece?

If the work is going on a wall, measure the available wall space first. A common gallery rule still holds up: artwork should take up about 60–75% of the wall width it hangs on. For example, if the wall is 120 cm wide, a canvas between 70 and 90 cm wide will usually feel balanced.

For commissions, always ask for wall dimensions. Guessing is how paintings end up being returned.

2. Decide on Orientation and Proportion

Next, think about orientation: portrait, landscape, or square. This should come from the subject. Tall figures, trees, and architecture often want vertical space. Wide scenes and narratives usually breathe better horizontally.

Now look at aspect ratio, which is simply the relationship between width and height. Common ratios include:

• 4:5 (great for portraits and classical compositions)
• 3:4 or 2:3 (versatile and familiar)
• 1:1 (square, modern, and graphic)

You don’t need to overthink this. Pick a ratio that supports the subject and stick with it. Many artists reuse the same proportions across multiple works for consistency.

3. Scale the Subject First

A practical trick is to decide how big the main subject should appear, then build the canvas around that. For example, if you’re painting a head-and-shoulders portrait and you want the head to be roughly 12 inches tall, add space around it for breathing room. That might naturally lead you to a 20 × 26 inches canvas rather than something smaller.

This approach works especially well for figurative and narrative painting. It keeps the subject dominant and avoids awkward cropping.

4. Factor in Viewing Distance

Canvas size should match how the work will be seen. Small, detailed paintings invite close viewing. Large canvases are meant to be read from across a room.

A rough guideline used in exhibition planning is that the ideal viewing distance is about 1.5 to 2 times the diagonal length of the canvas. If viewers can’t step back far enough, very large works can feel overwhelming or unreadable.

5. Think About Practical Limits

Be honest about your workspace, materials, and time. Large canvases cost more, take longer to cover, and require room to move around them. If you’re working alla prima or in short sessions, a mid-size canvas is often more realistic.

Also consider transport. If it doesn’t fit in your car or through a standard doorway, that’s a calculation you don’t want to ignore.

A Simple Formula You Can Use

If you want a quick, repeatable method:

• Decide the width based on wall space or subject scale.
• Choose an aspect ratio.
• Calculate the height using the ratio (for example, width ÷ 4 × 5 for a 4:5 format).
• Adjust slightly for standard canvas sizes to save money.