Separate preparation from application
Painting time depends heavily on surface condition and protection work. Moving items, masking, patching, sanding where appropriate, cleaning and priming can take as much time as applying the finish. Estimate those activities explicitly.
The Painting Time Planner asks for your own area and application rate. It does not claim that a universal square-metres-per-hour or square-feet-per-hour rate fits every surface, tool or skill level.
Do not invent drying or recoat times
Coatings vary. Temperature, humidity, ventilation, film thickness, surface and product chemistry can change the applicable waiting period. Use the product label or manufacturer’s technical instructions and any professional guidance that applies.
The calculator therefore treats the between-coat wait as an input. It can add the time to your schedule, but it does not decide what the safe or effective wait should be.
Plan for room use, not just the last brush stroke
Dry-to-touch, recoat and full cure can be different milestones. Furniture replacement, washing, heavy use or exposure may have different requirements. Follow the manufacturer for the specific product and surface rather than treating “dry” as one universal condition.