Reading scale from a reference

If a known object appears in the image, you can form a ratio between the image measurement and its actual size.

The calculator then scales any image measurement by the factor rac{ ext{real}}{ ext{image}}.

This is useful for printed diagrams, microscope images, screenshots, maps, and technical photography.

Practical tips

  • Measure both lengths in the same unit before entering the ratio.
  • Use the scale strip to confirm whether the real size should be much larger or only slightly larger.
  • When the reference is tiny, round carefully so the ratio error does not dominate the final answer.

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