How big can I print my image?

Jul 24, 2025

For an image to look as sharp as real life, it needs to have a resolution higher then that of the human eye: usually around 1 arcminute, or 1/60th of a degree.

$$ \text{Linear resolution} = \frac{\text{Distance}}{\text{1 radian}} \times 1 \text{ arcminutes} $$

$$ \text{Linear resolution }(\text{inches}) = \text{Distance (m)} \times 0.0115 $$

$$ \text{Features / Inch } = \frac{87}{\text{Distance (m)}} $$

For an image to look good at 1 meter, around an arms-length, it needs a feature size of 1/87th of an inch. A poster that’s going to be viewed from 2 meters can get away with half that, 1/43th of an inch. Something that’s going to be examined up close, say 50 cm, needs a resolution of 1/172th of an inch.

Importantly, the actual resolution of the image is often different from the size of the pixels. If an image looks pixelated when you zoom in, a good rule is to print with a pixels-per-inch of twice the desired resolution:

Undersampled image. Small features (stars) take up 2 pixels.

Viewing distance PPI 4 meters 43 pixels/inch 2 meters 87 pixels/inch 1 meter 170 pixels/inch 50 cm 350 pixels/inch 25 cm 700 pixels/inch

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