What DPI should I scan text documents at?

Answer: the best DPI you can afford.

But the problem of using more Dots Per Inch, is the more DPI you use, the more space it’ll take up on your hard drive.

I scan colour A4 documents at 150dpi, but that means an average output size of approx. 300kb.

So, I thought, let’s measure the scan quality for DPI settings of 200, 150, 100, 75 & 50.

The test document
Printout of a string of characters in the Times New Roman font from 4 point to 12 point.

The results:
50 DPI – Even the 12 point is getting close to unreadable.
50 dpi scanned text

75 DPI – 10 point is readable, 8 point is a bit blurry.
75 dpi scanned text

100 DPI – 8 point is much better.
 100 dpi scanned text

150 DPI – 4 point is just readable.
150 dpi scanned text 

200 DPI – 4 point is readable.
200 dpi scanned text

So in summary

DPI setting

Minimum readable font size

File size kb
(TIF file)

File size kb
(JPG file)

50

12

161

72

75

8 – 10

286

155

100

6

482

255

150

4 – 6

770

512

200

4

1250

789

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