Square Footage Calculator for Rooms
Calculate a room’s square footage or combine multiple measured sections. Choose a simple shape or an L-shape, subtract missing areas, and add a separate material allowance. A 10 × 10 ft outline minus a 4 × 6 ft missing corner is 76 sq ft before extra material.
Build your measured area
Add rooms or sections, choose their shapes, and subtract openings or excluded spaces.
How this calculator works
Each section uses the visible formula for its selected shape. Added sections are combined, excluded sections are subtracted, and the optional material allowance is applied last. Results are shown in square feet, square yards, and square meters.
Worked example
A 15 × 12 ft room is 180 sq ft. Add a 10 × 8 ft closet and subtract a 3 × 4 ft opening to get 248 sq ft measured. A 10% flooring allowance raises the planning total to 272.8 sq ft.
L-shaped room: subtract the missing corner
Hypothetical measurement example: the 10 × 10 ft enclosing rectangle is not all usable floor. Remove its 4 × 6 ft missing corner: 100 − 24 = 76 sq ft. Check the same answer by adding two non-overlapping rectangles: 6 × 10 + 4 × 4 = 60 + 16 = 76.
To reproduce this in the calculator, select Feet and L-shape. Enter outer length 10, outer width 10, cutout length 4 and cutout width 6. Leave extra at 0% for measured area alone. With an entered 10% material allowance, planned coverage becomes 83.6 sq ft; carton rounding and a cutting layout are separate decisions.
Draw the outline before entering dimensions
Sketch the space and label each measured edge. Break irregular rooms into non-overlapping rectangles, triangles, circles, or trapezoids. Add occupied areas and subtract only true exclusions, checking that no section is counted twice.
Measure in one unit system throughout the project. Convert inches or centimeters before combining sections, and preserve the measured area separately from any material allowance.
Area is only the first purchasing input
Flooring, tile, paint, roofing, and landscape materials each translate area into packages differently. Use the net square footage here, then apply product coverage, layout waste, coats, depth, or regional pricing in the relevant calculator. Supplier package coverage controls the final order.
Shapes, units, and privacy
The builder supports rectangles, squares, triangles, circles, trapezoids, and L-shapes. It converts inches, meters, and centimeters to square feet using standard unit relationships. Your project is stored locally in this browser for convenience and is not saved to a CalcCaddy account.
Frequently asked questions
How do I handle an irregular room?
Add several simple shapes or select the L-shape option. Use a subtract section for openings, stairwells, islands, or other spaces that are not part of the project.
When should I add waste?
Material projects often need extra for cuts, breakage, matching, and future repairs. Straight layouts may need less; diagonal patterns and complex rooms may need more. Confirm the product instructions.
Can I share my project?
Yes. The Share and Copy actions include the project inputs in the link. The calculator performs the math in your browser without requiring an account.