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Canvas math
Three calculators for the numbers that trip people up before the first stroke: how many pixels a print needs, how large a canvas will print, and how dense a screen really is.
Print size to canvas pixels
How the print calculator works
Pixels are the only thing a drawing app really stores. A print size turns into pixels with one multiplication: the size in inches times the DPI (dots per inch, which printers and apps also call PPI). An 8 x 10 inch print at 300 DPI needs 2400 x 3000 pixels. Add bleed, the extra margin a printer trims away, to both sides of each dimension before multiplying: with 0.125 inch of bleed on every edge the same print becomes 8.25 x 10.25 inches, or 2475 x 3075 pixels.
Metric sizes work the same way after dividing by 2.54 (centimeters) or 25.4 (millimeters). A4 is 210 x 297 mm, which is about 8.27 x 11.69 inches, so at 300 DPI it needs roughly 2480 x 3508 pixels. With 3 mm of bleed per edge that grows to about 2551 x 3579 pixels. The calculator rounds to the nearest whole pixel.
Set the canvas size before you start drawing. Scaling a finished painting up adds blur, and scaling it down later is easy, so when in doubt start larger. Our longer guide on canvas size and DPI for print walks through crops and aspect ratios.
Canvas pixels to print size
Reading a canvas the other way round
The second calculator answers the question in reverse: you already have a 3000 x 4000 pixel painting and want to know how large it can print. Divide each side by the DPI. At 300 DPI that painting prints at 10 x 13.33 inches; at 200 DPI it stretches to 15 x 20 inches, which many people find acceptable for a poster. The aspect ratio shown beside the result helps you match a frame or paper size without cropping the composition.
Screen pixel density (PPI)
Why screen PPI matters for pen displays
Pixel density is the diagonal resolution divided by the diagonal size. A 13.3 inch pen display with a 1920 x 1080 panel lands around 166 PPI, sharp enough that individual pixels are hard to see at drawing distance. The same 1080p resolution on a 21.5 inch display drops to about 102 PPI, where thin lines can look stepped. A 27 inch 4K monitor sits near 163 PPI. When you compare displays, compare density as well as size, and read our notes on pen displays versus pen tablets before deciding.
Questions people ask
Is 300 DPI always required for print?
No. 300 DPI is a safe default for prints viewed at arm’s length, such as books and small art prints. Large posters seen from across a room often look fine at 150 DPI. Ask the print shop what it prefers.
Does DPI change anything on screen?
No. A screen only shows pixels. The DPI number in a file is a note for the printer about how large to print those pixels.
How much bleed should I add?
Many printers ask for 0.125 inch (about 3 mm) on every edge, but some want more. Their spec sheet wins.
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