Free Proportion Calculator for Artists

A proportion calculator answers a practical studio question: how should a reference be enlarged or reduced to fit a new canvas, paper, panel, or wall? For large wall projects, you can use our dedicated mural scaling calculator. This proportional scale calculator also works as a proportional resize calculator when you know the source and target dimensions. It compares the full width and height of both surfaces, reports the scale applied on each axis, and shows whether the target preserves the source shape. This is especially useful before drawing a transfer grid because equal cell counts do not prevent distortion when the two outer rectangles have different proportions.

A 2× width factor means the target is twice as wide as the reference; a 2× height factor means it is twice as tall. When both factors agree, the enlargement is proportional. When they differ, the target would stretch the composition unless you crop the reference, add borders, or change one target dimension. You can check the source and target aspect ratios first to see the exact proportional difference. Art Grid Maker reports both values rather than hiding the mismatch behind a single average, so you can correct the plan before marking the surface.

After confirming the overall proportions, choose how many squares to draw across the reference and target. The calculator divides each side by that count and returns the physical cell dimensions in inches, centimeters, or millimeters. Mark those measurements carefully with a ruler, keep every line square to the edge, and transfer landmarks between corresponding cells. Quick-scale buttons are useful for testing common enlargements, while custom dimensions handle real-world surfaces.