Area measurement

Gross Floor & Lot Area Calculator

Calculate a rectangular building floor, room or lot area and convert the result into common property-area units.

What this calculator estimates

Calculate rectangular floor or site area and unit conversions. It combines the inputs below to produce Calculated gross area. Every assumption remains editable so the estimate can reflect the property, financing and location being evaluated.

Worked example

Using the displayed sample assumptions, the calculator produces 5,000 sq. ft.. This is an illustration, not a market quote. Change one input at a time to understand what drives the result.

Inputs and assumptions

• Length — sample input: 100 ft
• Width — sample input: 50 ft
• Number of equal-sized levels — sample input: 1 levels
• Openings or area deductions — sample input: 0 sq. ft.

How to interpret the result

Confirm the measurement standard required for the assignment. Compare a conservative case with an expected case and keep a record of the assumptions used.

Common mistake to avoid

Do not combine above-grade, below-grade and rentable areas without labels. Local definitions, taxes, lending practices and measurement requirements can materially change the result.

Related calculators

Reviewed 2026-09-08.