Construction

Square Footage Calculator

This Square Footage Calculator helps you calculate the area of various shapes (squares, rectangles, circles, triangles, trapezoids) and convert between different units of measurement (square feet, square inches, square yards, square meters, acres, hectares). Also includes a price calculator to estimate costs for materials.

Quick Tips

Click to show tips

Try an Example

Pick a scenario to see how the calculator works, then adjust the values

Living Room

Calculate the area of a typical living room

Key values: 20 × 15 ft · Rectangle · 300 ft²

Circular Patio

Calculate the area of a round patio or garden bed

Key values: 12 ft diameter · Circle · ~113 ft²

Triangular Garden

Calculate the area of a triangular garden plot

Key values: 10 × 12 × 8 ft · Triangle · ~40 ft²

Documentation

Documentation Contents

Understanding Square Footage

Calculate area for common shapes and convert results across multiple units.

This calculator estimates the area for six shapes: rectangle, rectangle with border, circle, circle with border, triangle, and trapezoid. You can choose a measurement unit, calculate area in several units at once, and optionally estimate material cost using a price per area.

Inputs Glossary

Field-by-field guide to what each input means.

Input	What to Enter	Notes
Shape	Rectangle, Rectangle Border, Circle, Circle Border, Triangle, Trapezoid	Controls which dimensions appear.
Measurement Unit	cm, in, ft, yd, m	All dimensions use the selected unit.
Rectangle	Length, Width	Basic area input.
Rectangle Border	Length, Width, Border Width	Calculates the border area around a rectangle.
Circle	Diameter	Radius is derived from diameter.
Circle Border	Diameter, Border Width	Calculates the ring area.
Triangle	Side A, Side B, Side C	Uses Heron's formula with three sides.
Trapezoid	Parallel Side A, Parallel Side B, Height	Height is the perpendicular distance between sides.
Quantity	Number of identical areas	Multiplies total cost.
Price	Price per selected unit	Set to 0 if you only need area.
Price Per	Per square meter, foot, inch, or yard	Matches the unit used for cost calculation.

How to Use This Calculator

Follow these steps to calculate area and cost.

Select a shape from the buttons.
Choose your measurement unit.
Enter the required dimensions for the selected shape.
Optional: enter quantity and price to estimate total cost.
Click Calculate to see results, or Reset to clear.

Shape Guide and Formulas

The formula used for each shape.

Rectangle

Inputs: length, width.

Formula: $A = L \times W$

Rectangle Border

Inputs: length, width, border width.

Formula: $A = (L \times W) - (L - 2b) \times (W - 2b)$

Circle

Input: diameter.

Formula: $A = \pi \times (d/2)^2$

Circle Border

Inputs: diameter, border width.

Formula: $A = \pi \times (r^2 - (r - b)^2), \; r = d/2$

Triangle

Inputs: sides A, B, C.

Formula: $s = (a + b + c)/2$ , $A = \sqrt{s(s-a)(s-b)(s-c)}$

Trapezoid

Inputs: parallel sides A and B, height.

Formula: $A = (a + b)/2 \times h$

Cost Estimate

Use price per unit to estimate material cost.

Quantity multiplies the total cost for multiple identical spaces or pieces.
Price Per uses the matching area unit (square meter, foot, inch, or yard).
The Total Cost card only appears when a price is provided.

Interpreting Results

How to read the outputs on the results screen.

The main results show square feet and square meters, plus total cost if provided.
The conversions panel lists square inches, square yards, acres, and hectares.
The Quick Rectangle Calculator always uses feet, regardless of the main unit selection.

Worked Examples

Step-by-step calculations with real numbers.

Example 1: Rectangular Living Room

A living room measures 20 ft long by 15 ft wide.

$A = 20 \times 15 = 300 \text{ ft}^2$

Converted: 300 ft² = 27.87 m² = 43,200 in² = 33.33 yd²

At $5.50/ft² for hardwood flooring with 1 quantity: $1,650.00 total.

Example 2: Circular Patio

A circular patio has a diameter of 12 ft.

$A = \pi \times (12/2)^2 = \pi \times 36 \approx 113.10 \text{ ft}^2$

Converted: 113.10 ft² = 10.51 m² = 16,286.02 in²

At $8.00/ft² for pavers: $904.78 total.

Example 3: Triangular Garden Bed

A triangular garden bed has sides of 5 m, 6 m, and 7 m.

$s = (5 + 6 + 7)/2 = 9$ , $A = \sqrt{9 \times 4 \times 3 \times 2} = \sqrt{216} \approx 14.70 \text{ m}^2$

Converted: 14.70 m² = 158.22 ft² = 17.58 yd²

At $12.00/m² for mulch with 2 beds: $352.77 total.

Example 4: Trapezoid Driveway Section

A driveway section has parallel sides of 10 ft and 6 ft with a height of 4 ft.

$A = (10 + 6)/2 \times 4 = 32 \text{ ft}^2$

Converted: 32 ft² = 2.97 m² = 4,608 in² = 3.56 yd²

Applications

Common uses for area calculations.

Construction

Flooring and tile estimation
Paint and drywall planning
Project cost estimates

Real Estate

Room or home size comparisons
Listing and appraisal prep
Space planning

Landscaping

Seed or sod calculations
Mulch or gravel coverage
Garden layout planning

Frequently Asked Questions

Common questions about area calculations.

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

Break the room into basic shapes like rectangles, triangles, or circles. Calculate the area of each shape separately, then add them together for the total square footage.

What is the difference between square feet and square meters?

One square meter equals approximately 10.764 square feet. Square feet are commonly used in the US and UK for real estate, while square meters are the international standard (SI unit).

How much extra flooring material should I buy?

Purchase 10–15% more material than the calculated area to account for cuts, waste, and pattern matching. For diagonal installations, add 15–20% extra.

Does this calculator account for walls and obstacles?

This calculator computes raw geometric area. Subtract the footprint of permanent fixtures such as fireplaces, columns, or built-in cabinets from the total for an accurate usable-area figure.

Why does the triangle calculation sometimes show no result?

The three sides must satisfy the triangle inequality: the sum of any two sides must be greater than the third side. If this condition is not met, a valid triangle cannot be formed and no area is returned.

Measurement Accuracy

Accuracy tips and limitations.

Use consistent units. Convert mixed measurements before entering values.
Triangle sides must satisfy the triangle inequality, or no result will be shown.
Border widths should be smaller than half of the shape dimensions to avoid invalid geometry.
Results are rounded to 6 decimal places.
Measurement standards like gross vs livable area vary by region. This calculator reports raw geometric area.