Quick answer
GSM is mass per area, not finished thickness. Core, finish, compression, and sleeves change real stack height, so measure samples before locking an insert.
Creator workflow
Capture the actual specification, quote, or platform setting for your project, then use the related calculation with those values rather than a generic market assumption.
Common mistakes
Do not treat a category label, supplier term, or platform policy as a universal product specification. Confirm the current version, territory, and contract terms that apply to you.
Related calculators
Limits
This is educational planning material, not supplier, legal, tax, or platform advice.