Example 1
- Side a: 10
- Side b: 5
50.00
A 10 by 5 floor: fifty square units of covering.
Rectangle area calculator
Give the two sides that meet at a right angle. You get the floor, the frame, or the homework rectangle in cm² or in². A room 10 by 5 is 50.00; the same product covers a desktop, a tile, or a sheet as long as both edges share one unit.
A = a × b. A cube is on the cube volume calculator. A triangle is on the triangle area calculator.
Result
Side a (cm) and Side b (cm). Area shows up here.
How it works
Rectangle area is the product of two edges that meet at a right angle. The formula is short, P = a·b, and we do not add a diagonal or a third dimension. Sides in centimeters give square centimeters. Sides in inches give square inches. The unit switch changes the result label and leaves the numbers you typed alone.
The first card example is a 10 by 5 room. Ten times five is 50.00, that many square units of flooring or floor paint. A thin strip 15 by 2 is still a rectangle and gives 30.00. Side order does not matter: 4 by 8 and 8 by 4 are both 32.00. With 6 and 9 you get 54.00; with 11 and 3 the area of one tile is 33.00 before you multiply by how many pieces you need.
The form has two fields, a and b. Type length and the width perpendicular to it, in the same unit, then Calculate. A comma and a period are the same, so 7.5 can be 7,5. The result uses two decimal places. For a square, type the same side twice: 7 and 7 is 49.00, because a square is a rectangle with equal edges.
A triangle with base 10 and height 5 has area 25.00, exactly half of this rectangle. That lives on the triangle area page. A cube of edge 5 has volume 125, a third dimension on another calculator. Perimeter 2(a+b) is not printed here either: for 10 and 5 the perimeter is 30 and the area is 50.
Mixing centimeters with inches in one run breaks the scale. Both sides in cm or both in inches. The switch does not convert a typed 10 into inches. If you need tiles with grout, this calculator gives the area of one rectangular surface; piece count and joints belong elsewhere.
A circle inscribed in a 10 by 5 rectangle is a different formula. Circle area with π has its own page. Here you stay with a times b, two dimensions, and nothing from the height of a box.
How to use
- Type side a, for example the length of a room, a frame, or a sheet, in cm or inches.
- Type side b in the same unit, the width perpendicular to a. For a square, repeat the same side.
- Click Calculate. 10 and 5 give 50.00 with a cm² or in² label, matching the unit switch.
- If you need volume, open the cube or prism page. This page stays two-dimensional.
- Work out perimeter 2(a+b) on paper or elsewhere. For 10 and 5 the perimeter is 30 and the area is 50.
Formula
A = a × b
Keep both sides in one unit. A third dimension is volume on another page.
A = a × b at 10 by 5
Two sides at a right angle. A room 10 by 5 is 50.00. A narrow 8 by 3 strip is 24.00.
- A
- Area a × b. 10 × 5 = 50.00. 12 × 4 = 48.00. A third dimension is volume on another page.
- a
- First side. 10 with b = 5 gives 50. 7 with 7 gives 49, the same product for a square.
- b
- Second side. 5 with a = 10. 3 with a = 8 is 24.00.
Examples
Example 2
- Side a: 8
- Side b: 3
24.00
A narrow 8 by 3 strip, typical of a frame rail.
Example 3
- Side a: 12
- Side b: 4
48.00
A 12 by 4 sheet, for example a paper band.
Example 4
- Side a: 7
- Side b: 7
49.00
A 7 by 7 square. Equal sides are allowed.
Example 5
- Side a: 15
- Side b: 2
30.00
A 15 by 2 strip when one edge is much longer.
Example 6
- Side a: 6
- Side b: 9
54.00
A 6 by 9 rectangle; side order is free.
Example 7
- Side a: 11
- Side b: 3
33.00
An 11 by 3 tile, area of one piece before you multiply by count.
Example 8
- Side a: 4
- Side b: 8
32.00
The same area as 8 by 4, with the sides swapped.
Frequently asked questions
What is a 10 by 5 room?
50.00. That is area, the product of the sides. The sum 15 would be an incomplete perimeter; the full perimeter is 30.
Can I use this for a 7 by 7 square?
Yes. A square is a rectangle. 7 times 7 is 49.00. A cube of edge 7 (343) is on the cube volume page.
How is this different from box volume?
This page uses two dimensions. A box or cube needs height. With edge 5 the face area is 25 and cube volume is 125.
Does a 10 by 5 triangle have the same area?
It has half. A triangle with base 10 and height 5 has area 25.00. The 10 by 5 rectangle has 50.00.
Does swapping a and b change the result?
No. 4 times 8 and 8 times 4 are 32.00. The page does not sort the sides.
Can I mix centimeters and inches?
Not in one run. Both sides in cm or both in inches. The unit switch changes the result label and does not convert typed numbers.
Can I use this area for floor tiles?
Yes, as the area of one rectangular surface. Tile count and grout belong on the tile calculator.
Where is rectangle perimeter?
Perimeter is 2(a+b). For 10 and 5 it is 30 and the area is 50. This formula only multiplies the sides.
What do 6 by 9 and 15 by 2 give?
6 times 9 is 54.00. A thin strip 15 by 2 is 30.00. Both are ordinary rectangles.
Is a circle inscribed in a 10 by 5 rectangle included?
No. Circle area with π is on the circle page. Here only a times b.
Knowledge sources
The calculator computes the same formula as the definition below.
Page updated in 2026.