Most spools do not need drying every time
It is common advice to dry filament before every print, but that habit costs real time and, on some materials, over-drying can make filament more brittle rather than helping it. The more useful question is whether this specific spool, given its material, storage history, and any symptoms you have already seen, shows a real signal worth acting on. This tool triages that question from a few practical inputs instead of defaulting to "always dry" or "never dry."
How the triage works
Materials differ in how hygroscopic they are: Nylon and TPU absorb moisture readily, PETG is a middle case, and PLA and ABS/ASA are comparatively less sensitive. That baseline combines with your storage condition and any symptom you have observed, since audible popping, stringing, or a rough surface are some of the more reliable signs of moisture already in the filament. A high combined signal recommends drying before your next print; a low signal recommends printing normally and watching for issues rather than spending time drying proactively.
Worked example
PETG stored on an open shelf for 10 days with no reported symptoms lands in a mixed middle zone: the tool suggests either a short precautionary dry or printing a small test piece first, rather than a confident "dry" or "skip it" answer, since the signal is real but not strong.
A common mistake
A frequent error is drying a spool once and assuming it stays dry indefinitely afterward. A spool left back out on an open shelf, even after a successful drying cycle, reabsorbs moisture over time in a humid environment. If your storage conditions have not changed, expect to revisit drying periodically rather than treating one cycle as a permanent fix.
Limitations
This is a triage tool based on reported symptoms and storage history, not a moisture-content measurement. It cannot replace a filament dryer's own readout, a scale-based drying test, or your own experience with a specific brand's behavior; treat an ambiguous result as a genuine ambiguity, not a hidden certainty.