Abstract
To determine the character sizes suitable for comfortable reading, we compared the legibility of sentences and the reading speed. We used reading materials with several font sizes (from 4 to 30 point of Microsoft Mincho). In Experiment 1 participants evaluated the legibility for Japanese sentences with the questionnaire. The legibility increased with the font size between 4 and 12 point. In Experiment 2, we extended the font size up to 30 point, and found the legibility decreased with that between 20 and 30 point. In Experiment 3 participants read aloud Japanese sentences as fast as they could (with no errors). Reading speed increased with the font size between 4 and 6 point, but did not increased with that between 6 and 15 point. Together with our previous findings, we conclude that character sizes suitable for comfortable reading are approximately between 10 and 20 point (visual angle 0.46～0.92°)．
