Add rectangles, triangles, circles, L-shapes, and trapezoids in one list. Subtract islands and obstacles. Forward the total to the paint, flooring, tile, drywall, sod, mulch, or gravel calculator.
Inches accept fractions: 12 5/8, 12-5/8, or 12.625
| Area | Mode | Sq ft |
|---|---|---|
| Rectangle 12 × 14 ft | add | 168.00 |
| Total | 168.00 | |
12 5/8, 12-5/8, or 12.625.Formula reference
- Rectangle:
length × width - Triangle:
base × height / 2 - Circle:
π × radius²(orπ × (diameter / 2)²) - L-shape:
rect 1 + rect 2(one row, four dimensions) - Trapezoid:
(side a + side b) / 2 × height - Total:
Σ added rows − Σ subtracted rows
Use the per-row add / subtract toggle to remove kitchen islands, columns, or any cut-out from the total.
Conversions
| From | To | Multiply by |
|---|---|---|
| ft² | m² | 0.09290304 |
| m² | ft² | 10.7639104167 |
| ft² | yd² | ÷ 9 |
| ft² | in² | × 144 |
| ft² | acres | ÷ 43,560 |
| m² | hectares | ÷ 10,000 |
| acres | hectares | 0.4046856422 |
FAQ
How do I enter 5 and a half inches? Any of three forms work: 5 1/2, 5-1/2, or 5.5. The parser also accepts a bare fraction (1/2). Pick in as the unit on the dimension's selector.
Should L-shapes use the dedicated row or two rectangles? Either works and both give the same total. Use the L-shape row when the two parts share a wall and you want them grouped on the shopping list; use two rectangles when the shapes are physically separate (kitchen + dining).
When do acres and hectares appear? Acres and hectares show only when the total is at least 1,000 ft² (about 93 m²). Below that scale the conversion is rarely useful and only adds noise to the result.
Why is the drywall button hidden by default? Drywall is sized by wall area (perimeter × height), not floor area. The button shows only when a rectangle row is present so the destination calc can read the room footprint.
Describe the task to the AI assistant and continue from the result.
Open AI assistant →How the math works for every shape
Square footage is area. The five formulas you actually need:
- Rectangle:
length × width— rooms, patios, pads. - Triangle:
base × height / 2— gables, corner cut-outs. - Circle:
π × radius²— pools, firepits. Diameter input →π × (d/2)². - L-shape:
rect 1 + rect 2— kitchen-plus-dining as one row. - Trapezoid:
(a + b) / 2 × height— bay windows, building lots.
The total is Σ add rows minus Σ subtract rows, so islands, columns, and stair openings come off the floor count automatically.
Worked example — irregular living room
A 14×16 ft main room with a 6×4 ft alcove and a 3×4 ft kitchen island that does not need flooring:
- Main rectangle:
14 × 16 = 224 ft² - Alcove rectangle:
6 × 4 = 24 ft² - Subtract island:
3 × 4 = 12 ft² - Total:
224 + 24 − 12 = 236 ft²(about21.93 m²)
This is exactly the number you forward to the flooring calculator or the tile calculator — click the matching button in the result block and your sqft rides along in the URL.
Worked example — backyard with a firepit
An 80×50 ft yard with a 12 ft diameter firepit cut-out:
- Yard rectangle:
80 × 50 = 4,000 ft² - Firepit circle:
π × (12/2)² ≈ 113 ft² - Sod area:
4,000 − 113 ≈ 3,887 ft²(≈361 m², 0.0892 acres)
Above 1,000 ft² the calc also shows acres and hectares — the unit sod and mulch suppliers quote. The sod, mulch, and gravel calculator buttons appear once the total clears 500 ft².
Scale reference
Quick anchors: a typical 12×14 bedroom is 168 ft² (15.6 m²); a 2,400 ft² home is 223 m² or 0.0551 acres; a 1-acre lot is 43,560 ft² or 0.405 hectares. Conversion factors: ft² → m² × 0.0929, ft² → yd² ÷ 9, ft² → in² × 144, ft² → acres ÷ 43,560.
Common questions
How do I type a fractional inch?
Three forms work: 5 1/2, 5-1/2, or 5.5. Bare fractions like 3/4 parse too. Set the unit selector to in; the calc converts to feet internally.
L-shape row or two rectangles?
Mathematically identical. Use L-shape when the rectangles share a wall and you want them grouped on the printed list. Use two separate rectangles when the rooms are physically apart — the shopping list then prints them as distinct line items.
When do acres and hectares appear?
Only when the total is at least 1,000 ft² (about 93 m²). Below that the conversion is noise — a 168 ft² bedroom does not need an acreage number. For lots over half an acre the figure is what your surveyor or municipality already uses.
Why is the drywall button sometimes hidden?
Drywall is sized by wall area, not floor area — the destination calc needs length and height, not just sqft. The button shows up only when a rectangle row is in the list, because rectangles carry the dimensions a drywall calc can split into walls.
Estimator only. Measure twice on real walls — corners drift, walls aren’t perfectly parallel, and floor plans round up. The concrete calculator and paint calculator both consume the square footage from this widget when you click their button in the result.
