Fraso / nomograms

Reprographics

Print size

Pixel dimension and output resolution against printed size.

A print size nomogram: three vertical scales, px (300 to 12000) on the left, L (12.7 to 4233) in the middle and dpi (72 to 600) on the right. A straight line laid across any two scales cuts the third at the value that satisfies L = px ÷ dpi × 25.4.12000100008000600050004000300025002000170014001000800600500400300pxpx728090100110130150170200220250300330400440500600dpidpi42333000200015001000800500400300200150100805040302012.7Lmm

Readings

px
dpi
mm

Drag the red line, or type into any two boxes — the third is solved. The marked box is the one being solved for.

Print at 100% scale, then check the 100 mm bar with a rule before trusting a reading.

Why this one is an instrument

The recurring question is not what size a file prints at but how big you can go before the resolution becomes indefensible, which means sliding one end and watching the other two. The 300 and 150 dpi marks sit on the same scale as everything between them, so the compromise is a position rather than a verdict.

Equation
L = px ÷ dpi × 25.4
Ranges
px 300–12000 px · dpi 72–600 dpi
Reading
Any two values fix the third. Outside the printed ranges the instrument stops being valid — that is what the end marks are for.

These are drawn from the stated equation and nothing else. Where an equation is itself an approximation — hyperfocal distance and tap drill sizes both are — the instrument inherits that approximation exactly, no better and no worse.