Example 1
- Unit: feet
- 12 ft × 10 ft
120 sq ft
12 × 10 = 120 sq ft, or 11.1484 m².
Square Footage Calculator
Enter length and width in the unit you choose. The calculator multiplies the sides and shows the area plus the other unit. A 12×10 ft room is 120 sq ft (11.1484 m²). 15×12 ft is 180 sq ft. In meters, 5×4 is 20 m².
Result
Enter the room length and width. The area will appear here.
Clean rectangle area without waste or a price. Material with contingency belongs on floor area. Unit conversion only: m² to square feet.
How results are calculated
L12 ft
W10 ft
A120 sq ft
The square footage calculator counts a clean rectangle. The formula is length × width. Sides in feet give sq ft. Sides in meters give m². The second result line converts the same area with 1 m² = 10.7639 sq ft.
A 12×10 ft room is 120 sq ft, or 11.1484 m². A 15×12 ft room is 180 sq ft. In meters, 5×4 is 20 m² (215.2782 sq ft). A 3×3 m square is 9 m².
Enter the side unit, then length and width. A comma in 4.5 works the same as a period. Zero and negative numbers are rejected.
This is not floor area with waste and a price — that page adds material contingency. A bare conversion of an area you already know belongs on the unit converter. The perimeter of the same 5×4 m rectangle is 18 m on the perimeter page.
Keep meters in the meter field, not centimeters: 400 cm is 4. The result does not subtract windows or doors. Split an irregular shape into rectangles and sum the areas separately.
Enter 12 and 10, click Calculate, and match 120 sq ft. Then 15 and 12: 180 sq ft. In meters, 5 and 4: 20 m².
How to use this calculator
- Keep feet if you measured the room in feet, or switch to meters.
- Enter length and width, for example 12 and 10. The result is 120 sq ft.
- Check the other unit: 120 sq ft is 11.1484 m².
- In meters enter 5 and 4. The result is 20 m², or 215.2782 sq ft.
- Waste and price belong on floor area. This page stays a clean rectangle.
Formula
A = L × W · 1 m² = 10.7639 sq ft
5 × 4 m = 20 m² (215.2782 sq ft). 12 × 10 ft = 120 sq ft (11.1484 m²). 3 × 3 m = 9 m².
Area and units
Rectangle area is length times width. 12 × 10 ft is 120 sq ft. 5 × 4 m is 20 m².
- A
- Area. 12 × 10 ft = 120 sq ft. 15 × 12 ft = 180 sq ft. 5 × 4 m = 20 m².
- m²
- Square meter. 1 m² = 10.7639 sq ft. 20 m² = 215.2782 sq ft.
- sq ft
- Square foot. 120 sq ft = 11.1484 m². This is not an acre.
- waste
- Not on this page. Material contingency belongs on floor area.
Examples
Example 2
- Unit: feet
- 15 ft × 12 ft
180 sq ft
15 × 12 = 180 sq ft. Same formula, larger sides.
Example 3
- Unit: meters
- 5 m × 4 m
20 m²
5 × 4 = 20 m², or 215.2782 sq ft.
Related calculators
Frequently asked questions
How is rectangle area calculated?
The calculator multiplies length by width. At 5 m and 4 m the result is 20 m². At 12 ft and 10 ft the result is 120 sq ft. The second line shows the same area in the other unit.
Which unit should I use for the sides?
Meters or feet — matching the unit field. Four hundred centimeters is 4 m, not 400. Entering 400 with meters treats the side as 400 m.
How does the other-unit line work?
It is the same area after conversion. 1 m² is 10.7639 sq ft. 20 m² is 215.2782 sq ft. 120 sq ft is 11.1484 m².
Does the result include waste or a material price?
No. This page stays a clean rectangle. Waste and a price per square meter belong on the floor-area page.
Is a window or door opening subtracted?
No. This page counts the rectangle only. Openings belong on floor area or in a separate deduction.
How is this different from the m² to sq ft converter?
The converter starts from an area you already know. Here you enter two sides and the area is built from them.
Does a comma in 4.5 work?
Yes. A comma and a period are the same fraction. At 4.5×4 m the result stays 18 m².
What is the primary result?
Area in the side unit you chose, for example 20 m² or 120 sq ft. The other unit appears beside it.
Are zero or negative numbers accepted?
No. Length and width must be greater than zero. An empty field also yields no result.
Where do I calculate trim or boards?
Trim on the room-perimeter page: 5×4 m is 18 m. Boards take m² from floor area, not from this clean rectangle alone.
Knowledge sources
Rectangle area is length times width. 1 m² = 10.7639 sq ft (NIST).
Page updated October 12, 2026.