Square Footage Calculator
Adjust the inputs below. Results update as you type.
How it works
Rectangle: L × W. Circle: πr². Triangle: ½bh. L-shape: split into two rectangles, sum areas. Measure room to the inside walls and exclude closets if calculating paint needs (add them back for flooring). Subtract windows and doors for paint (about 20 sq ft each). Flooring contractors add 10% waste; tile in diagonal pattern needs 15%. 1 square foot = 144 square inches = 0.0929 m².
Input guidance
- Confirm date/time/unit settings before comparing outputs.
- If a task has optional fields, run both with and without them to understand impact.
- Save scenario variants when making practical decisions.
The formula
Square footage = length × width for rectangles. For complex spaces, divide into rectangles, calculate each, and add. Convert from inches by dividing by 144.
Worked example
A 12 ft × 15 ft room is 180 square feet. An L-shaped space is split into two rectangles whose areas are summed.
More examples to test
- Quick-pass example: run default assumptions for a first estimate.
- Refined example: update one assumption at a time to isolate impact.
How to interpret results
Use outputs as operational estimates and pair them with local constraints, business rules, or provider requirements.
When this can be inaccurate
Utilities can miss local policy details, special-case rules, and environment-specific constraints.
Change history
- July 2026: Quality-reviewed for publication with formula checks and explanatory copy updates.
Site-wide corrections also appear on the corrections log.
Find productivity tools for everyday workflows
General recommendation, not professional advice.
Frequently asked questions
How do I calculate square footage?+
Multiply length by width in feet. For rooms that are not rectangular, break them into rectangles and add the areas together.
How do I handle odd shapes?+
Divide the area into rectangles and triangles, compute each, and sum. Triangles are ½ × base × height.
Why add extra for flooring?+
Cutting, waste, and pattern matching mean you should buy about 5–10% more material than the exact square footage.
Why are outputs slightly different from another tool?+
Different tools can use different rounding rules, default assumptions, and treatment of edge cases.
How can I improve estimate reliability?+
Use verified inputs from real records and re-run calculations after major assumption changes.
Guided next steps
Want the full workflow? Use this calculator inside a step-by-step guide.