Square Footage Calculator

The basic idea is straightforward: measure the length and width of a space, then multiply. That gives you area in square feet, as long as you measured in feet to begin with. If you measured in inches, divide your result by 144. If you used yards, multiply by 9.

For most rooms, you'll want a tape measure and something to write with. Measure the longest wall (length) and the wall perpendicular to it (width). Multiply those two numbers. Done. A room that's 12 feet long and 10 feet wide is 120 square feet.

Things get trickier with L-shaped rooms, oddly angled spaces, or areas with cutouts like closets or alcoves. The easiest approach there is to break the space into smaller rectangles, calculate each one separately, and add them together. Subtract any sections you're not actually measuring, like a column or a structural bump-out.

The core formula for a rectangle or square is:

Area = Length × Width

That covers the majority of rooms and lots you'll ever need to measure. But different shapes call for different formulas. Here's a quick breakdown:

• Rectangle or Square: Area = Length × Width
• Triangle: Area = (Base × Height) ÷ 2
• Circle: Area = π × Radius² (use 3.14159 for π)
• Trapezoid: Area = ((Base 1 + Base 2) ÷ 2) × Height
• Ellipse: Area = π × Semi-Major Axis × Semi-Minor Axis

As long as all your measurements are in feet, the result will be in square feet. Mixed units are where people run into trouble, so double-check everything before you multiply.

Most spaces aren't perfectly rectangular. Yards, lots, oddly designed rooms, and landscaping projects often involve shapes that require a little more thought.

Rectangles and Squares are the easiest. Plug in length and width and you're done.

Triangles come up more often than you'd expect, especially with attic spaces, pitched roof sections, or triangular garden beds. Measure the base and the height (the perpendicular distance from the base to the tip), then use the formula: (Base × Height) ÷ 2.

Circles are common for round patios, pools, or garden features. Measure the diameter (straight across the center), divide by 2 to get the radius, then calculate π × r². A circular patio with a 10-foot diameter has a radius of 5 feet, so the area is about 78.5 square feet.

Trapezoids show up in properties with non-parallel boundaries or rooms with one angled wall. Add the two parallel sides together, divide by 2, then multiply by the height between them.

For really irregular shapes, sketch the space on paper and divide it into combinations of the shapes above. Add the areas together. It's a bit tedious but it works reliably.

Not everyone measures in feet. Here's a handy reference for converting between square feet and other common area units:

If you're working with metric measurements, remember that 1 meter equals roughly 3.281 feet, so a square meter is about 10.76 square feet. That difference adds up fast when you're covering a large area.

It helps to have some real-world reference points. Here are typical square footage ranges for common spaces:

• Small bathroom: 35 to 50 sq ft
• Standard bedroom: 120 to 200 sq ft
• Master bedroom: 200 to 300 sq ft
• Average kitchen: 100 to 175 sq ft
• One-car garage: 200 to 240 sq ft
• Two-car garage: 400 to 480 sq ft
• Average U.S. apartment (1-bedroom): 700 to 900 sq ft
• Average U.S. single-family home: around 2,300 sq ft
• Standard parking space: approximately 162 sq ft (8.5 × 19 ft)
• Basketball court (NBA): 4,700 sq ft

These ranges aren't exact standards, they vary by region, era of construction, and design style. But they give you a useful gut-check when you're evaluating a space or comparing listings.

Once you have your square footage, you can start translating it into material quantities and project budgets. The process is pretty consistent regardless of what you're doing.

Most materials are sold by the square foot or can be converted to it easily. Flooring, tile, carpet, paint, roofing shingles, and sod are all priced this way. Multiply your square footage by the material's cost per square foot to get a rough estimate.

Always add a waste factor. For tile and hardwood, that's typically 10 percent extra to account for cuts, breakage, and pattern matching. For carpet, 15 percent is common because of the way rolls are cut. For paint, check the coverage rate on the can (usually 350 to 400 square feet per gallon) and divide your wall area by that number.

Here's a simple process to follow:

1. Measure the area and calculate square footage.
2. Add your waste percentage (10 to 15 percent for most materials).
3. Multiply the adjusted square footage by the cost per square foot.
4. Add in labor costs if you're hiring out the work.
5. Include any delivery, installation, or disposal fees.

Getting two or three quotes from contractors is smart, but having your own square footage number gives you a baseline to verify those quotes against. If a contractor's estimate seems wildly off, check their math first.

Sometimes you need to work in a different unit, especially when dealing with international specs, real estate listings in metric countries, or large tracts of land measured in acres.

Here are the key conversions you'll use most often:

• Square feet to square inches: multiply by 144
• Square feet to square yards: divide by 9
• Square feet to square meters: divide by 10.764
• Square feet to acres: divide by 43,560
• Square feet to hectares: divide by 107,639

Going the other direction, just reverse the operation. To convert square meters to square feet, multiply by 10.764. To convert acres to square feet, multiply by 43,560.

A practical tip: if you're buying a piece of land described in acres and you want to picture it, one acre is roughly the size of a football field without the end zones. About 43,560 square feet. That mental image helps a lot when you're standing on a property and trying to gauge the size.

Square footage calculations come up constantly in everyday life, even when you're not actively thinking about them.

Real estate is the most obvious one. Listing prices, price per square foot comparisons, and property tax assessments all rely on accurate measurements. Buyers use it to compare value across properties; sellers use it to price competitively.

Home improvement projects are another big one. Flooring installation, painting, tiling, roofing, and insulation all require accurate square footage to estimate materials and costs. Getting this wrong in either direction costs money.

Interior design and furniture planning use square footage to ensure pieces fit the space properly and that the room doesn't feel cramped or empty. Knowing your room dimensions before you shop saves a lot of back-and-forth returns.

HVAC and energy calculations depend on square footage to size heating and cooling equipment correctly. An undersized unit runs constantly and still struggles; an oversized one short-cycles and wastes energy.

Landscaping and lawn care require area measurements for seeding, sodding, fertilizing, and applying pesticides or herbicides. Product rates are almost always given per 1,000 square feet.

Even something as routine as renting a storage unit involves square footage. A 10×10 unit is 100 square feet, a 10×20 is 200. Knowing how much you're storing and how those numbers translate helps you pick the right size without paying for space you don't need.