Measure Once, Order Right
Flooring, paint, sod, tile, roofing — nearly every home project is bought by the square foot, and nearly every ordering mistake starts with bad area math. This free square footage calculator handles four shapes — rectangle, circle, triangle and trapezoid — in feet or meters, and converts the result to ft², m², acres and square inches, with an optional cost estimate.
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4 shapes · Cost estimate
Please enter dimensions greater than zero.
Area
For flooring, tile or sod, add 5–10% waste for cuts and breakage. Irregular rooms: split them into rectangles and add the pieces — or measure the two longest runs and treat offcuts as waste allowance.
How to Use the Calculator
- Pick the shape closest to your space. Rectangles cover most rooms; circles handle round patios and pools; triangles and trapezoids cover gables, bays and wedges.
- Enter dimensions in feet or meters — measure to the nearest inch for ordering.
- Add a cost per ft² (optional) for an instant budget number on flooring, turf or tile.
Area Formulas
Circle: π × (diameter/2)²
Triangle: ½ × base × height
Trapezoid: (a + b) ÷ 2 × height
Worked examples: 12 × 10 ft room = 120 ft². 10 ft diameter circle = π × 25 = 78.5 ft². Triangle 10 × 8 = 40 ft². Trapezoid (10+14)/2 × 6 = 72 ft².
Common Room Sizes
| Room | Typical size | Area |
|---|---|---|
| Small bedroom | 10 × 10 ft | 100 ft² |
| Master bedroom | 14 × 16 ft | 224 ft² |
| Living room | 16 × 20 ft | 320 ft² |
| 2-car garage | 20 × 22 ft | 440 ft² |
Who Calculates Square Footage
- Homeowners ordering flooring, paint, sod or mulch.
- Contractors turning site measurements into material lists and quotes.
- Renters & buyers sanity-checking listing sizes.
- Gardeners sizing beds, lawns and patio projects.
Pro tips
- Add 5–10% waste for flooring and tile — cuts, breakage and pattern matching eat material.
- For L-shaped rooms, split into two rectangles and add them.
- Measure the longest runs; small jogs and closets can usually ride inside the waste allowance.
Worked Example: An L-Shaped Room, Step by Step
Irregular rooms are just rectangles in disguise. Take an L-shaped bedroom: the main block is 16 × 10 ft and the foot of the L is 8 × 6 ft.
- Main block: 16 × 10 = 160 ft².
- Foot of the L: 8 × 6 = 48 ft².
- Total: 160 + 48 = 208 ft².
- Add waste: at 10%, 208 × 1.10 = 228.8 — order about 229 ft² of material.
Same trick works for cut-outs and closets: measure the full rectangle, subtract what is not floor, and add the waste allowance at the end.
Measuring in Feet and Inches
Real rooms rarely measure in whole feet. Convert the inches to a decimal before you multiply: divide by 12, then add. The classic slip is writing 12 ft 6 in as 12.6 ft — it is actually 12.5 ft, and that extra tenth quietly inflates every figure downstream. Worked: a 12.5 × 10 ft room is 12.5 × 10 = 125 ft², not 126.
Wall Area for Paint: Subtract the Openings
Paint covers walls, not openings — so doors and windows come off the total. One wall is 12 × 8 ft = 96 ft². Subtract a standard door (21 ft²) and a window (12 ft²): 96 − 21 − 12 = 63 ft² of paintable wall. Run that number through our paint calculator to turn it into gallons, with coats and coverage built in.
Frequently Asked Questions
How do I calculate square footage of a room?
Multiply length by width (both in feet). A 12 × 10 ft room is 120 ft². For odd shapes, break the space into rectangles, circles or triangles and add the pieces.
How many square feet is a 10×10 room?
100 ft² — 10 × 10. Common for small bedrooms and kitchens.
How do you convert square meters to square feet?
Multiply by 10.7639. So 20 m² = 215.3 ft². The calculator converts automatically when you switch unit systems.
What is the difference between square feet and linear feet?
Linear feet measure length (a 10-ft board); square feet measure area (a 10×10 ft room = 100 ft²). You can’t convert one to the other without a second dimension.
How much extra flooring should I order?
5–10% over the net area for straight layouts; up to 15% for diagonal patterns or rooms with many jogs.
How many acres is my lot?
Divide square feet by 43,560. A 10,000 ft² lot is about 0.23 acres. The calculator shows acres automatically.
How do I calculate the square footage of an L-shaped room?
Split the L into two rectangles, work out each area, and add them. A room made of a 16 × 10 ft section and an 8 × 6 ft section is 160 + 48 = 208 ft². Add about 10% for cuts and waste when you order material — roughly 229 ft² for this room.
How do I convert feet and inches to square feet?
Divide the inches by 12 and add them as a decimal: 12 ft 6 in is 12.5 ft, not 12.6 ft. Then multiply as usual — a 12.5 × 10 ft room is 125 ft². Writing 12.6 instead quietly inflates every measurement that follows.
Final Thoughts
Area math is simple; ordering mistakes are expensive. Measure carefully, add your waste factor, and let the calculator handle the conversions — your wallet will notice the difference.
Try our tile calculator for layout and waste.