Nominal screen size is not the active area: pixel density of e-readers under 5 inches, 2026

E-reader screens are sold by a rounded diagonal, in inches. Pixel density, in pixels per inch (PPI), is a property of the active area, the rectangle that contains the pixels. Dividing a pixel count by the nominal inch size therefore answers a different question from the one the PPI figure claims to answer. This note gives the method, applies it to the one pocket-reader panel in the set whose pitch and active area are published, and then back-calculates the active-area diagonal implied by other makers' published resolution and PPI. For IKAWE Moov Pro the pitch is 0.08467 mm, the active area is 58.25 × 96.86 mm (4.450 inches on the diagonal), and both routes give 299.99 PPI(~300PPI). Dividing the same pixels by the nominal 4.5 inches gives 296.7 PPI. A sourced specification table of e-readers under 5 inches is included. IKAWE makes Moov. Competitor figures are taken from makers' pages and the cited reports. No competing device was measured for this note.