How do I calculate square footage?

For a simple rectangular room, multiply the length by the width, both measured in feet: square footage = length × width. This calculator extends that same idea to L-shaped rooms, circles, triangles, and multiple rooms totaled together.

How do I calculate the square footage of an L-shaped room?

Measure the room as if it were one large rectangle (the outer length and width), then measure the rectangular notch that's missing from one corner. Subtract the notch's area from the outer rectangle's area: L-shape area = (outer length × outer width) − (cutout length × cutout width).

How do I calculate the area of a circle?

Area = π × radius². This calculator asks for diameter (the distance straight across the circle, which is usually easier to measure) and divides it by 2 to get the radius automatically.

How do I calculate the area of a triangle?

Area = (base × height) ÷ 2, where height is the perpendicular distance from the base to the opposite point — not the length of a slanted side. This works for any triangle, not just right triangles.

How do I total the square footage of multiple rooms?

Calculate each room's area separately using the shape that matches it, then add all the areas together. This calculator does that automatically — add an area for each room or space, and the total (plus a breakdown of each one) updates instantly.

What's the difference between square feet, square meters, and square yards?

They're all area units on different scales: 1 square yard = 9 square feet, and 1 square meter ≈ 10.76 square feet. Square feet is standard for US flooring and paint estimates, square yards is common for carpet pricing, and square meters is standard outside the US.

Why does the calculator include a waste factor?

A waste factor adds a buffer for material cut off during installation — trimming around edges, cuts for irregular shapes, or matching patterns. It's optional here since square footage itself doesn't need waste, but it's useful when you're using this total to shop for a material like flooring or paint.

How accurate is the L-shape calculation?

It's exact for a room that's a simple rectangle with one rectangular notch removed from a corner (the most common L-shaped room layout). For more complex, multi-notch, or curved floor plans, break the space into simpler shapes using multiple areas and add them together.

Is my data stored anywhere?

No. All calculations run locally in your browser using standard JavaScript arithmetic. Nothing you enter is transmitted to a server or stored.

Square Footage / Area Calculator

Find the area of a rectangle, L-shape, circle, or triangle, and total multiple rooms at once — in sq ft, sq m, or sq yd, with cost.

Last updated August 3, 2026

Enter dimensions in

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Area 1

= 120.0 sq ft

Waste factor (%)

Estimate cost

Total area

132.0 sq ft

120.0 sq ft before waste factor

How to use the area calculator

1
Pick a shape for your first area: Rectangle, L-shape, Circle, or Triangle.
2
Enter its dimensions — each shape shows only the fields it needs.
3
Click "Add another area" for each additional room or space — the total updates automatically with a full breakdown.
4
Choose sq ft, sq m, or sq yd for your results, and optionally add a waste factor and price to estimate cost.

Area formulas, with examples

Every shape reduces to one of these formulas — an L-shape is just a rectangle with a smaller rectangle subtracted from a corner.

1. Rectangle

Formula: length × width

Example: A 14 ft × 11 ft bedroom is 14 × 11 = 154 sq ft.

2. L-shape

Formula: (outer length × outer width) − (cutout length × cutout width)

Example: A room measures 16 ft × 12 ft overall, but a 5 ft × 4 ft corner is missing (say, for a closet that juts into the space). Area = (16 × 12) − (5 × 4) = 192 − 20 = 172 sq ft.

3. Circle

Formula: π × radius² (radius = diameter ÷ 2)

Example: A circular patio 12 ft across (diameter) has a radius of 6 ft. Area = π × 6² = π × 36 ≈ 113.1 sq ft.

4. Triangle

Formula: (base × height) ÷ 2

Example: A triangular flower bed with a 10 ft base and a 6 ft height is (10 × 6) ÷ 2 = 60 ÷ 2 = 30 sq ft.

5. Multi-room total

Formula: sum of every individual area

Example: A 154 sq ft bedroom plus a 172 sq ft L-shaped living room plus a 60 sq ft closet totals 154 + 172 + 60 = 386 sq ft — exactly what this calculator does automatically when you add multiple areas.

Sq ft vs. sq m vs. sq yd

1 unit	Equals	Commonly used for
1 sq ft	0.111 sq yd, 0.0929 sq m	US flooring, paint, drywall, real estate listings
1 sq yd	9 sq ft, 0.836 sq m	Carpet pricing, landscaping fabric
1 sq m	10.764 sq ft, 1.196 sq yd	Everywhere outside the US

Need to convert a single value between other units too — like inches to centimeters, or pounds to kilograms? The Unit Converter covers length, weight, volume, and more.

What to do with your square footage

Once you have an accurate total, plug it straight into a material-specific calculator to turn square footage into an actual shopping list:

Painting a room? The Paint Calculator converts wall area into gallons or liters needed.
New flooring? The Flooring Calculator turns floor area into the number of boxes to buy.
Hanging drywall? The Drywall Calculator converts wall (and ceiling) area into sheet count, plus joint compound, tape, and screws.
Building a patio? The Paver / Patio Calculator turns patio area into paver count, base material, and sand.
Sizing an air conditioner or heater? The BTU Calculator turns room area into the right cooling or heating capacity.

Since every one of those calculators includes its own length × width inputs, this Area Calculator is most useful up front — for irregular L-shaped rooms, circular spaces, triangular areas, or adding up several rooms before you start shopping for material.

Frequently asked questions

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