How should you use a project calculator?
Begin with finished dimensions from the actual project area, not a plan that may have changed. Break irregular spaces into simple rectangles, triangles or individual runs and calculate each one separately. Keep units consistent, and measure openings, transitions and obstructions that materially change quantity.
The calculator result is a planning takeoff. Suppliers may sell only whole bags, boxes, panels or stock lengths, so purchase quantities are rounded up. Product-specific coverage, local codes, installation methods and site conditions remain the final authority.