Room Area Calculator

Find a room floor area and perimeter at once. Enter the room size to get square footage for flooring and linear feet for baseboard or trim.

floor areaperimeter = green border (door gap)
Floor Area
sq ft
Floor square footage.

Usage Tip

Sketch the room and note each wall length. The perimeter here is the full loop — subtract about 3 ft for each doorway when buying baseboard.

THE MATH
Floor area = Length × Width
Perimeter = 2 × (Length + Width)
Totals = per-room values × number of rooms
Floor area (square feet) sizes flooring, underlayment, and ceiling materials. Perimeter (linear feet) sizes baseboard, shoe molding, and crown.
This assumes rectangular rooms; break an L-shape into rectangles and total them.
Add a waste factor when you order the actual material — this gives the bare room area and perimeter.
Subtract door openings from the perimeter for baseboard (roughly 3 ft per standard door), and skip walls where trim is not run.
For flooring the floor area is what matters; for paint you want wall area instead (perimeter times wall height).
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The calculators and tools on Formula Factory are provided for general guidance and informational purposes only. Results are estimates based on standard formulas and the values you enter — they do not constitute professional engineering, electrical, or architectural advice. Always verify calculations with a qualified professional before making decisions for any safety-critical, code-compliance, or commercial application. Formula Factory makes no representations or warranties as to the accuracy or completeness of any result, and accepts no liability for errors, omissions, or any outcomes arising from reliance on this information.