Layer Line Visibility Estimator
A layer height that looks rough in your hand can disappear entirely once a part sits somewhere it's actually viewed from.
The math behind the estimate
Each layer creates a small step on any angled or curved surface, and how visible that step is depends on the angle it subtends in your field of view — smaller in absolute terms, but also smaller relative to your eye's resolving power, the farther away you stand. This calculator converts layer height and viewing distance into that angular size and compares it against roughly where average human visual acuity stops resolving fine detail.
Real-world visibility depends on more than geometry
Glossy or light-colored surfaces show layer lines more readily than matte or dark ones, raking light (light hitting the surface at a low angle) makes lines far more visible than direct overhead light, and curved surfaces show stepping more than flat ones printed parallel to a layer. Treat this as a starting estimate for "will this matter," not a guarantee for every lighting condition and finish.
When it's worth dropping to a finer layer height
A display piece, a close-up handheld object, or anything with curved surfaces viewed up close benefits most from a finer layer height. A large functional part, something mounted overhead, or anything viewed from a normal standing distance often looks completely fine at a much coarser (and much faster-printing) layer height than intuition suggests.