How to use the Canvas Size Calculator
- Choose your units. Press inches, cm or mm. If you switch units after typing, the numbers convert so the canvas stays the same physical size.
- Type the width and height. Width goes first. The ⇄ button flips portrait to landscape, and the Popular sizes chips load common US and European canvases in one tap.
- Read the results. You get the size in the other two units (plus the nearest ⅛ inch when you work in metric), the area, the perimeter, the diagonal and the simplified aspect ratio next to the closest familiar ratio.
- Check the nearest standard canvases. The table lists the two closest US stock sizes and the three closest French Figure, Paysage or Marine sizes, with the difference in width and height. Click a size to load it.
- Get a feel for the size. The drawing beside the inputs is to scale. Use Compare with to stand the canvas next to an A4 or Letter sheet, a 170 cm person, or hang it over a sofa. Then press Copy summary to paste every number into a supplier email or your notes.
Why canvas sizes don’t translate cleanly
An inch is exactly 2.54 cm, so the arithmetic is easy. The trouble is that the two markets stock different sizes. US canvases come in whole inches, European canvases in whole centimeters, and the two systems rarely meet. A 30 × 40 cm canvas is 11.81 × 15.75 in. The nearest US stock size, 12 × 16 in, measures 30.48 × 40.64 cm — about 5 mm wider and 6 mm taller. That’s close enough for a painting, but not for a ready-made frame cut to fit snugly.
Proportions shift too. A 16 × 20 in canvas is 4:5, an 18 × 24 is 3:4 and a 24 × 36 is 2:3. Move a composition from one to another and something has to be cropped or stretched, so it pays to check the ratio before you buy. If you’re enlarging a sketch to a new support, the Aspect Ratio Calculator works out the missing side.
Area is what catches people out most. Doubling both sides quadruples the surface: 12 × 16 in is 192 square inches, while 24 × 32 in is 768. Paint, gesso, varnish and shipping weight all follow that number rather than the width — and so does your price if you charge by the square inch, which is worth running through the Art Pricing Calculator before you commit to a large piece.
The French standard adds a third logic. Each number from 0 to 120 fixes the long side and then offers three short sides: Figure for portraits, Paysage for landscapes and Marine for long seascapes. A No. 10 is 55 cm long in all three versions, at 46, 38 or 33 cm wide. Many European suppliers still label stretchers this way, so “F10” on an order form means 46 × 55 cm.
US and French sizes that almost match
When you ship work abroad or order stretcher bars from a European supplier, these are the pairs worth knowing. The gap is measured side by side after matching the long sides.
| US canvas | In centimeters | Closest French size | Gap per side |
|---|---|---|---|
| 11 × 14 in | 27.94 × 35.56 cm | F5, 27 × 35 cm | 9 mm and 6 mm |
| 18 × 24 in | 45.72 × 60.96 cm | P12, 46 × 61 cm | 3 mm and under 1 mm |
| 24 × 36 in | 60.96 × 91.44 cm | M30, 60 × 92 cm | 10 mm and 6 mm |
| 12 × 16 in | 30.48 × 40.64 cm | F6, 33 × 41 cm | 25 mm and 4 mm |
| 16 × 20 in | 40.64 × 50.8 cm | P10, 38 × 55 cm | 26 mm and 42 mm |
The 18 × 24 in and P12 pair is the one to remember: for most purposes they are the same canvas. A 16 × 20 in painting has no good French twin and falls between F8 and P10, although the plain metric 40 × 50 cm comes within 8 mm. Going the other way, the popular European 50 × 70 cm (19.69 × 27.56 in) sits awkwardly between 20 × 24, 20 × 30 and 22 × 28 in, so plan on a custom frame. The full list of stock sizes in both systems lives in the Standard Canvas Sizes Chart.
Tips from practice
List artwork height first. The calculator asks for width first because that’s how most software thinks, but galleries, auction houses and museum catalogs give dimensions as height × width × depth. A landscape painted 20 in wide and 16 in tall goes on the label as 16 × 20 in.
Measure the canvas you actually have. Nominal sizes are nominal. Store-bought canvases can run slightly over or under, and a thick gallery profile changes what fits in a floater frame. Measure the real edges before ordering a frame or a custom box.
Pick the depth before you pick the frame. Standard ¾ in (1.9 cm) bars are meant to go into a frame; gallery bars of 1½ in (3.8 cm) are meant to hang bare with painted sides. The depth also changes the fabric you cut: a 16 × 20 in canvas needs 21.5 × 25.5 in of raw canvas on standard bars and 23 × 27 in on gallery bars.
Photograph for the ratio, not just the megapixels. A 24-megapixel camera makes 6000 × 4000 pixel images in 3:2. Shoot a 16 × 20 in painting with it and the short side limits you to 4000 pixels across 16 inches, which is 250 DPI rather than 300. That still prints well at arm’s length; for a full 300 DPI, stitch two overlapping shots.
Check the diagonal before moving day. When you tilt a canvas through a doorway or into a car, the diagonal is the number that has to fit. A 24 × 36 in canvas is 43.3 in (110 cm) corner to corner, and the frame adds more.