Calculate the area of any room, wall, or space — rectangles, L-shapes, circles & triangles. Instant unit conversions.
How to Use This Square Footage Calculator
Select your shape from the dropdown — rectangle for standard rooms, L-shape for rooms with an alcove or bump-out, circle for round patios or ponds, and triangle for gable walls or angled corners. Enter your measurements in feet (convert inches to decimals: 6 inches = 0.5 ft). The calculator instantly shows the area in square feet plus conversions to square yards (for carpet), square meters, and acres (for land). If you're buying materials, add a waste factor of 5-15% — the result updates to show how much to actually order.
How to Calculate Square Footage: The Complete Guide
Square footage is the foundation of nearly every home improvement estimate. Whether you're buying flooring, ordering paint, laying sod, or listing a house for sale, it all starts with knowing the area. The good news: for most spaces, it's just length times width. The complications come with irregular shapes, unit conversions, and knowing which square footage number you actually need. Here's everything you need to measure any space accurately.
The Basic Formula: Length × Width
For any rectangular or square space, square footage = length (ft) × width (ft). A bedroom that measures 14 feet by 11 feet is 14 × 11 = 154 square feet. That's it. The only trick is making sure both measurements are in the same unit — feet. If you measured in feet and inches, convert the inches to a decimal fraction of a foot first:
| Inches | Decimal Feet | Inches | Decimal Feet |
|---|
| 1" | 0.083 | 7" | 0.583 |
| 2" | 0.167 | 8" | 0.667 |
| 3" | 0.250 | 9" | 0.750 |
| 4" | 0.333 | 10" | 0.833 |
| 6" | 0.500 | 11" | 0.917 |
Measuring Irregular and L-Shaped Rooms
Real rooms aren't always perfect rectangles. The universal technique for any irregular shape is divide and conquer: break the space into simple rectangles, calculate each area, and add them up. An L-shaped living room becomes two rectangles. A room with a bay window becomes a rectangle plus a small trapezoid or triangle. Draw the room on graph paper, split it along logical lines, measure each section, and sum the areas. Our calculator's L-shape mode handles the two-rectangle case automatically — for more complex rooms, calculate each rectangle separately and add the results.
Formulas for Other Shapes
- Circle: Area = π × radius². The radius is half the diameter. A circular patio 10 ft across (5 ft radius) is 3.14159 × 5² = 78.5 sq ft. Useful for round patios, fire pits, ponds, and above-ground pools.
- Triangle: Area = ½ × base × height. A triangular gable wall with a 24 ft base and 8 ft peak height is ½ × 24 × 8 = 96 sq ft. Essential for gable-end siding, angled room corners, and triangular garden beds.
- Trapezoid: Area = ½ × (base₁ + base₂) × height. For shapes with two parallel sides of different lengths, like an angled driveway or a pie-shaped lot.
- Circle border/ring: (π × outer radius²) − (π × inner radius²). For circular walkways or pool decks around a round pool.
Gross Living Area vs. Material Square Footage: They're Different
This trips up a lot of homeowners. There are two common "square footage" numbers for a house, and they're measured differently:
- Gross Living Area (GLA): Used in real estate listings and appraisals. Measured from the exterior walls of heated/cooled living space, following the ANSI Z765 standard. Excludes garages, unfinished basements, and open-to-below areas (like a two-story foyer). This is the number on your listing and tax records.
- Material Square Footage: Used for flooring, paint, and renovation takeoffs. Measured from the interior walls, room by room, of the actual surfaces you're covering. This number is smaller than GLA because it excludes wall thickness — but for flooring you'd also subtract cabinets and fixtures, while for paint you'd measure wall area (perimeter × height) rather than floor area.
Never use your home's listed GLA to order flooring — you'll over-order. Always measure the actual rooms you're working on.
Unit Conversion Reference
| From Square Feet | Operation | Used For |
|---|
| → Square Yards | ÷ 9 | Carpet |
| → Square Meters | × 0.0929 | Metric material specs |
| → Acres | ÷ 43,560 | Land, lots |
| → Squares (roofing) | ÷ 100 | Roofing, siding |
| → Square Inches | × 144 | Small precise areas |
Why Add a Waste Factor?
The square footage of your room is not the amount of material to buy. Every material project generates waste: cuts at the edges, mistakes, defective pieces, and future repairs. Standard waste factors: 5-10% for simple rectangular rooms with straight-lay flooring, 10% for standard tile, 15% for diagonal patterns or herringbone, and 15-20% for rooms with many corners, angles, or obstacles. Always round up to full boxes or units. Buying an extra box now is cheaper than a special dye-lot-matched order later when you're short two tiles.