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Square Footage Calculator

Estimate square footage from length, width, outer length with the Square Footage Calculator.

Choose a floor-plan shapeCalculate common enclosed, bordered, circular, and polygonal areas in one workspace.
12 options
SQUARE FOOTAGE120 ft²

length × width. Only inputs needed by this operation are shown.; quantity 1; total 120.0000 ft²; estimated cost $0.00.

Estimate based on the values shown
MethodSelectable floor and site area formulas in feet. Results support quantity, diameter/border-width variants, radians, area output units, and per-area pricing.

Before you use the result

Check the entered units and assumptions before using the result for purchasing, construction, engineering, or safety decisions.

CALCULATOR GUIDE

How to use the Square Footage Calculator

Estimate square footage from length, width, outer length with the Square Footage Calculator. It includes Rectangle, Rectangle border, Circle, Ring, Triangle with Base & Height, Trapezoid workflows, so choose the one that matches the values you actually know. Use it to check a practical estimate, paying close attention to the selected units and assumptions.

Step by step

  1. For the Square Footage, enter length, width, outer length, outer width, inner length. Keep each value in the unit displayed beside its field.
  2. Review the selected Square Footage workflow and inputs, then read square footage in the result panel.
  3. Change one Square Footage assumption at a time to compare scenarios. Use Reset to restore this tool's worked example values.

How the calculation works

Selectable floor and site area formulas in feet. Results support quantity, diameter/border-width variants, radians, area output units, and per-area pricing.

Worked example

In the Square Footage worked example, length 12 ft, width 10 ft, outer length 14 ft, outer width 12 ft produces square footage of 120 ft². length × width. Review the displayed units before comparing the result.

Understanding the result

The Square Footage reports square footage. Use it to check a practical estimate, paying close attention to the selected units and assumptions. Check the entered units and assumptions before using the result for purchasing, construction, engineering, or safety decisions.

How to check the answer

Check the Square Footage result by reversing the conversion or recomputing square footage from length, width, outer length. For construction, electrical, weather, or purchasing decisions, compare the result with the applicable specification or professional guidance.

Common questions

What does the Square Footage calculate?

Estimate square footage from length, width, outer length with the Square Footage Calculator.

Which Square Footage inputs have the biggest effect?

square footage responds directly to length, width, outer length, outer width, inner length. Change one input while holding the others constant to see its effect.

Is the Square Footage result exact?

Check the entered units and assumptions before using the result for purchasing, construction, engineering, or safety decisions. Recheck length, width, outer length and use square footage only for a decision where that level of precision is appropriate.

Formula tests, limits, sources, and guide registry updated September 1, 2026.
INTERPRET THE RESULTRead the other guideCheck assumptions, limitations and comparison methods →