Area Calculator Tool
Use this area calculator to measure total surface area quickly in square feet, meters, or yards. Perfect for flooring, painting, landscaping, and construction planning.
For L-shaped or irregular areas, calculate each rectangle separately and add together · Enter all measurements in the same unit (feet) · For circles, enter the radius (half the diameter)
How to Use This Calculator
This area calculator computes square footage, square yards, square meters, and square inches for four common shapes. Select your shape, enter the measurements, and the results update instantly in all four units.
Shape Guide
- Rectangle / Square — enter length and width in feet. A square is just a rectangle where length = width. Use this for rooms, lawns, patios, and most construction areas.
- Triangle — enter the base (the bottom edge) and the perpendicular height (the vertical distance from base to apex). This is not the slant height — it must be the true vertical height.
- Circle — enter the radius (half of the diameter). If you know the diameter, divide it by 2 first. Use this for circular patios, round pools, garden features, and pipe cross-sections.
- Trapezoid — enter both parallel bases (top and bottom) and the perpendicular height between them. Common for triangular garden beds, angled walls, and irregular lots.
This calculator uses feet as the input unit. If your measurements are in inches, divide by 12 before entering. For mixed measurements (e.g. 14 ft 6 in), convert the inches to a decimal: 6 in ÷ 12 = 0.5 ft, so enter 14.5 ft. This prevents the most common calculation error — entering inches as if they were feet and getting a result that is 144 times too large.
Worked Examples
Example 1 — Rectangular Living Room (15×12 ft)
15 ft × 12 ft = 180 sq ft
In other units: 180 ÷ 9 = 20 sq yd · 180 × 0.0929 = 16.72 sq m
How to use this result: A flooring contractor quotes in sq yd — you need 20 sq yd. A tile supplier sells by the sq ft — you need 180 sq ft + 10% waste = 198 sq ft to order. A European supplier quotes per sq m — you need 16.72 sq m.
Example 2 — Triangular Garden Bed (base 14 ft, height 9 ft)
½ × 14 ft × 9 ft = 63 sq ft
How to use this result: For mulch at 2-inch depth: 63 sq ft × (2÷12) ÷ 27 × 1.10 = 0.43 cu yd of mulch needed. Use the Mulch Calculator with 63 sq ft as your area input.
Example 3 — Circular Patio (radius 8 ft)
π × 8² = 3.14159 × 64 = 201.06 sq ft
Note: If you only know the diameter (e.g., the patio is 16 ft across), the radius = 16 ÷ 2 = 8 ft. Always use the radius in this formula, not the diameter.
How to use this result: For concrete at 4-inch depth: 201.06 sq ft × (4÷12) ÷ 27 = 2.48 cu yd concrete. Use the Concrete Calculator for the full estimate.
Example 4 — L-Shaped Backyard
Section A: 30 ft × 20 ft = 600 sq ft
Section B: 15 ft × 12 ft = 180 sq ft
Total area = 600 + 180 = 780 sq ft
Strategy: For any L-shaped, U-shaped, or irregular area, divide into rectangles, calculate each, and sum. Sketch the shape on paper first and label each section with its dimensions before calculating.
Area Formulas by Shape
Quick reference for the six most common shapes in construction and landscaping.
| Shape | Formula | Example (ft) | Result |
|---|---|---|---|
| Rectangle | L × W | 15 × 12 | 180 sq ft |
| Square | Side² | 10² | 100 sq ft |
| Triangle | ½ × B × H | ½ × 10 × 8 | 40 sq ft |
| Circle | π × r² | π × 5² | 78.54 sq ft |
| Trapezoid | ½ × (B1 + B2) × H | ½ × (10 + 14) × 6 | 72 sq ft |
| Ellipse | π × a × b | π × 6 × 4 | 75.40 sq ft |
All measurements in the same unit (feet). For ellipses, a and b are the two semi-axes (half of each axis). The ellipse formula is not in the calculator — compute it manually using π × a × b.
Measuring Irregular Shapes
Most real-world spaces — L-shaped rooms, angled lots, odd-shaped gardens — don’t fit a single formula. The standard approach is to decompose the shape into simple sub-shapes, calculate each, and sum.
The Grid Method
Sketch the area on graph paper where each square = 1 ft × 1 ft. Count all full squares inside the boundary. For partial squares along the edge, count those that are more than half inside. This produces a reasonable estimate for curved or complex boundaries without needing formulas.
The Rectangle Decomposition Method
Draw the shape on paper. Add straight lines to divide it into rectangles and triangles. Measure each sub-shape, calculate its area, and sum all sub-areas. This is exact for any polygon (shape with only straight edges).
Irregular Lots and Land Parcels
For oddly shaped properties, the most accurate method is a survey. Property deeds in the US typically describe lot boundaries using metes-and-bounds descriptions or GIS coordinates. Your county assessor’s website often shows the lot area in square feet directly. For rough estimates, the rectangle decomposition method works well for most residential lots.
Our Square Footage Calculator lets you add multiple rectangular sections together in a single tool — ideal for L-shaped rooms, hallways added to rooms, or any space that requires combining multiple rectangular measurements.
Area Unit Conversions
Quick reference conversion table for the most common area units used in construction, real estate, and landscaping.
| From | To Square Feet | To Square Yards | To Square Meters | To Acres |
|---|---|---|---|---|
| 1 Square Foot | 1 sq ft | 0.1111 sq yd | 0.0929 sq m | 0.0000230 acres |
| 1 Square Yard | 9 sq ft | 1 sq yd | 0.8361 sq m | 0.000207 acres |
| 1 Square Meter | 10.7639 sq ft | 1.1960 sq yd | 1 sq m | 0.000247 acres |
| 1 Acre | 43,560 sq ft | 4,840 sq yd | 4,046.9 sq m | 1 acre |
| 1 Hectare | 107,639 sq ft | 11,960 sq yd | 10,000 sq m | 2.471 acres |
Area in Construction Projects
Once you know the area of a space, you can feed it directly into material calculators. Here’s a quick guide to how area is used across the most common construction and landscaping tasks.
| Project | Uses Area For | Typical Unit | Calculator |
|---|---|---|---|
| Flooring | Tile, hardwood, carpet quantity | sq ft | Flooring Cost |
| Painting | Wall area → gallons of paint | sq ft | Paint Calculator |
| Tile / Grout | Tiles and grout quantity | sq ft | Tile Calculator |
| Mulch / Topsoil | Cubic yards needed at given depth | sq ft | Mulch Calculator |
| Sod / Grass | Sod pallets needed | sq ft | Sod Calculator |
| Concrete slab | Cubic yards concrete + rebar | sq ft | Concrete Calculator |
| Landscape rock | Tons of gravel or rock | sq ft | Landscape Rock |
| Roofing | Squares of shingles | sq ft → squares (100 sq ft) | Roofing Calculator |
Measurement Tips for Accurate Area Calculations
Always Measure at the Widest Points
For material ordering, measure at the widest point of each dimension — not the average. When in doubt, round up. Running short of material mid-project and re-ordering from a different production batch can produce visible color differences in flooring, tile, and paint.
Re-Measure Before Ordering
Always measure twice (at a minimum) and record the measurements on a sketch. Small errors in a single measurement compound significantly when calculating area. A room that measures 15 ft × 12 ft is 180 sq ft, but a measurement error of just 6 inches on each dimension (14.5 × 11.5) gives 166.75 sq ft — a difference of 13 sq ft, enough to run short on a tile order.
Feet and Inches: Convert to Decimal First
If your tape measure reads in feet and inches, convert the inches to decimal feet before entering into the calculator. 3 inches = 0.25 ft. 6 inches = 0.5 ft. 9 inches = 0.75 ft. The most common mistake: entering 15 ft 6 in as 15.6 ft (wrong) instead of 15.5 ft (correct). 6 inches = 6 ÷ 12 = 0.5 ft.
Account for Waste Before Ordering Materials
Area gives you the theoretical quantity needed. Material calculators add a waste factor — 10% for tile, 10–15% for wallpaper, 5% for sod. Never order exactly the calculated area of material — always include a waste buffer. Our material calculators handle this automatically.