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Paper Enlarge & Reduce Ratio Calculator

Find the copier enlarge or reduce percentage between paper sizes. Just pick the original and target sizes—like A4 to A3 or A3 to A4—or enter a custom long edge, with a handy chart of common ratios.

Input

Original paper size (the document you are copying)

Paper size

Target paper size (the finished output)

Paper size

Result

Copy scaling from A4 to A3

141%

This is an enlargement

Original long edge297 mm
Target long edge420 mm
Scaling (exact value)141.41%

Quick reference for common copy scaling ratios

FromToScalingType
A4A3141%Enlarge
A3A471%Reduce
A4B4123%Enlarge
B4A482%Reduce
A4B587%Reduce
B5A4116%Enlarge
A3B487%Reduce
B4A3115%Enlarge
A4A4100%Same

How it works

  • The ratio is found from the long-edge ratio between the original and target paper. Because A- and B-series sheets share the same aspect ratio of roughly 1:1.41, the long-edge ratio equals the square root of the area ratio and works directly as the scaling percentage.
  • Common values are about 141% for A4 to A3, 71% for A3 to A4, 122% for A4 to B4, and 86% for A4 to B5. As on a copier, the result is rounded to a whole percentage.
  • For sizes not in the presets, choose 'Custom size' and enter the long edge in millimeters. You can set both the original and the finished size freely to compute the ratio.
  • A ratio of 100% means same size; above 100% is an enlargement and below 100% is a reduction. The result panel also labels whether you are enlarging or reducing.
  • When converting between sheets with different aspect ratios (such as photo sizes or squares), the long and short edges need different scaling, so the image may be cropped or leave margins.
  • Calculations use JIS standard dimensions in millimeters. Some copiers offer only stepped zoom levels, so choose the closest available setting.

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