Field guide
How big can an enlarged picture print?
Print size is a relationship between pixels and physical inches. Upscaling can create more samples for a printer, but it cannot make the source contain newly observed detail.
01
Divide pixel dimensions by the intended pixels per inch. A 3000-pixel edge produces ten inches at 300 ppi or twenty inches at 150 ppi.
02
Choose resolution from viewing distance. A hand-held print rewards 240–300 ppi, while a poster seen across a room can work with substantially fewer samples per inch.
03
Inspect faces, text and diagonal edges at the planned physical scale. Those features reveal interpolation softness and ringing earlier than sky or out-of-focus areas.
04
Ask the printer whether its size field changes metadata or resamples pixels. Setting 300 dpi in a label does nothing to image detail unless physical dimensions or pixel count also change.