Square Footage Calculator — Free Online Area Calculator

How to Use the Square Footage Calculator

1. Enter the length: Measure the length of the area you want to calculate using a tape measure, laser distance measurer, or architectural plans. Type the measurement into the Length field. For the most accurate results, measure to the nearest inch or tenth of a foot. If your area is not a perfect rectangle, measure the longest dimension and note any irregularities for separate calculation.
2. Enter the width: Measure the width of the area perpendicular to the length and type it into the Width field. Ensure both measurements use the same unit. For L-shaped rooms or complex spaces, break the area into separate rectangles, calculate each one, and add them together to get the total square footage.
3. Select your measurement unit: Choose the unit of your measurements from the dropdown menu. Options include feet (most common for US construction), inches (for smaller surfaces like countertops), meters (for metric-system projects), and yards (for landscaping and fabric). The calculator automatically converts your input to all output units.
4. Review area conversions: The results panel instantly displays the calculated area in square feet, square meters, square yards, square inches, acres, and hectares. Use square feet for US real estate and construction estimates, square meters for international projects and metric-system building codes, and acres for lot and land area calculations.

All results update in real time as you change any input. Experiment with different dimensions or units to quickly compare areas for renovation planning, material purchasing, or property evaluation.

Square Footage Formula

Variables Explained

• Length: The longer dimension of the rectangular area. In construction, this is typically measured along the longest wall of a room. For property lots, this is the dimension running parallel to the street or along the longer boundary line.
• Width: The shorter dimension of the rectangular area, measured perpendicular to the length. In a room, this is the distance from one wall to the opposite wall crossing the shorter span.
• Square Feet (ft²): The standard unit of area measurement in US real estate and construction. One square foot equals the area of a square measuring 12 inches on each side. This is the primary unit used for home valuations, rent calculations, and material ordering in the United States.
• Square Meters (m²): The metric unit of area measurement used internationally. One square meter equals approximately 10.764 square feet. This unit is standard in most countries outside the United States for real estate listings and construction specifications.
• Acres: A unit of land area equal to 43,560 square feet. Originally defined as the amount of land a team of oxen could plow in one day. Acres are commonly used for measuring lots, farms, parks, and undeveloped land in the United States.

Step-by-Step Example

Calculate the area of a living room that measures 18 feet 6 inches long by 14 feet 3 inches wide:

1. Convert to decimal feet: 18 feet 6 inches = 18.5 ft, 14 feet 3 inches = 14.25 ft
2. Calculate area in square feet: 18.5 x 14.25 = 263.63 sq ft
3. Convert to square meters: 263.63 x 0.092903 = 24.49 sq m
4. Convert to square yards: 263.63 / 9 = 29.29 sq yd

This living room has an area of approximately 264 square feet, which is a comfortable medium-sized living room suitable for a standard furniture arrangement including a sofa, coffee table, entertainment center, and two accent chairs.

Practical Examples

Example 1: Sarah's Flooring Project

Sarah is installing hardwood floors in her master bedroom that measures 16 feet by 13 feet. She needs to know the total area to order the right amount of flooring material. She enters the dimensions in feet:

• Area: 16 x 13 = 208 square feet
• With 10% waste factor: 208 x 1.10 = 228.8 square feet of flooring to order
• At $5.50 per square foot for engineered hardwood: 228.8 x $5.50 = $1,258.40 in materials

Sarah orders 229 square feet of hardwood flooring (rounded up) to account for cuts around the closet door, transitions, and any defective planks. The extra material also ensures she has matching planks available for future repairs.

Example 2: James's Deck Construction

James is building a new deck and needs to calculate the area for a deck that will be 24 feet long by 16 feet wide. He uses the square footage calculator to determine material quantities:

• Deck area: 24 x 16 = 384 square feet
• In square meters: 384 x 0.092903 = 35.67 m²
• Composite decking boards per square foot: 1.1 (including waste)
• Linear feet of decking needed: 384 x 1.1 / (5.5/12) = approximately 922 linear feet

With a 384-square-foot deck, James calculates his total material costs including composite boards, framing lumber, hardware, and railing. The square footage helps him get accurate quotes from contractors and compare the cost of composite versus pressure-treated wood decking.

Example 3: Emily's Property Evaluation

Emily is comparing two properties for purchase. Property A is listed as 0.35 acres and Property B as 18,000 square feet. She uses the calculator to put both in the same units for fair comparison:

• Property A: 0.35 acres x 43,560 = 15,246 square feet
• Property B: 18,000 square feet = 0.4132 acres
• Difference: 18,000 - 15,246 = 2,754 square feet larger (Property B)
• Property B is 18% larger than Property A

Despite the different units used in the listings, Emily now knows that Property B offers roughly 2,754 more square feet of lot space. She factors this into her price-per-square-foot comparison along with location, zoning, and building setback requirements to make an informed purchasing decision.

Example 4: Robert's Paint Estimation

Robert wants to paint the walls of his home office, which measures 14 feet by 11 feet with 9-foot ceilings. He calculates the wall area, subtracting the door and window openings:

• Total wall perimeter: 2 x (14 + 11) = 50 linear feet
• Wall area: 50 x 9 = 450 square feet
• Subtract one door (21 sq ft) and one window (15 sq ft): 450 - 36 = 414 sq ft of paintable surface
• One gallon covers 350 sq ft: 414 / 350 = 1.18 gallons (buy 2 gallons for two coats)

Robert purchases two gallons of paint to apply two coats on his 414 square feet of wall surface. With the floor area being 154 square feet (14 x 11), he also knows the room is large enough for a desk, bookshelf, and file cabinet without feeling cramped.

Area Conversion Reference Table

Conversions: 1 sq ft = 0.092903 sq m = 0.111111 sq yd = 144 sq in. 1 acre = 43,560 sq ft.

Tips and Complete Guide

Measuring Irregularly Shaped Rooms

Most rooms are not perfect rectangles. L-shaped rooms, rooms with bay windows, closet alcoves, or angled walls require a divide-and-conquer approach. Break the space into the fewest possible rectangles, measure each one separately, and add the areas together. For an L-shaped room, draw an imaginary line to divide it into two rectangles. Measure and calculate each rectangle, then sum them. For rooms with angled walls, create a rectangle that encloses the entire room and subtract the triangular areas in the corners. For curved walls, approximate the curve with a series of straight-line measurements. Accuracy within 2% to 3% is sufficient for most construction and material estimation purposes.

Square Footage in Real Estate

In real estate, square footage is the most important metric for property valuation and comparison. The price per square foot allows fair comparison between properties of different sizes in the same area. To calculate price per square foot, divide the property price by the total livable square footage. For example, a 1,800-square-foot home listed at $360,000 costs $200 per square foot. When comparing properties, ensure the square footage measurements use the same standards. Some listings include finished basement space while others do not, which can create misleading comparisons of up to 30% to 40% in apparent size.

Material Estimation from Square Footage

Once you know the square footage, you can estimate materials for almost any construction or renovation project. For flooring, add 10% to 15% waste factor. For painting, one gallon covers approximately 350 to 400 square feet with one coat. For carpet, add 10% for seams and pattern matching. For insulation, square footage directly determines the number of batts or bags of blown-in material needed. Our concrete calculator and tile calculator use square footage as a primary input for precise material quantity estimates.

Common Mistakes to Avoid

• Mixing measurement units: Entering the length in feet and the width in inches without converting will produce wildly incorrect results. Always ensure both dimensions use the same unit before multiplying, or use our calculator's unit selector which handles conversions automatically.
• Forgetting to subtract non-usable space: When calculating usable floor area, subtract the space occupied by structural columns, built-in features, stairs, and thick walls. For heating and cooling calculations, the full enclosed area is appropriate, but for furniture layout and flooring installation, the usable floor space matters more.
• Confusing total square footage with per-floor area: A two-story house with 1,200 square feet per floor has 2,400 total square feet of living space. Make sure you understand whether a measurement refers to a single floor or the entire home. Building footprint (the area the structure covers on the ground) differs from total living area in multi-story homes.
• Not accounting for waste in material orders: Ordering exactly the calculated square footage of flooring, tile, or other materials will leave you short after cuts, pattern matching, and defective pieces are factored in. Always add a waste factor of at least 10%, and 15% for diagonal installations or complex patterns.
• Rounding prematurely in chained calculations: When converting between units or multiplying for material estimates, keep full precision through intermediate steps and round only the final result. Rounding at each step can compound errors, especially in large-area calculations.

Frequently Asked Questions