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Area Calculator

Find the area of 17 shapes: rectangle, square, triangles, circle, ellipse, sector, segment, ring, trapezoid, parallelogram, rhombus, kite, regular polygons, irregular quadrilaterals and borders.

Change the values and press Calculate to work out your own figures.

Rectangle

Enter the length and width.

The longer side.
The shorter side.
The unit of every measurement; the answer is then also given in other units.
Result
Area of the rectangle
600 ft²
Perimeter
100 ft
Diagonal
36.05551275 ft

The area of the rectangle is 600 ft².

In other units
AmountUnit
55.741824m²
557,418.24cm²
600ft²
86,400in²
66.66666667yd²
0.01377410468acres
Show the working
  1. A = l × w
  2. Area = 600 ft²

Square

Enter the side.

The length of a side.
The unit of every measurement; the answer is then also given in other units.
Result
Area of the square
144 ft²
Perimeter
48 ft
Diagonal
16.97056275 ft

The area of the square is 144 ft².

In other units
AmountUnit
13.37803776m²
133,780.3776cm²
144ft²
20,736in²
16yd²
0.003305785124acres
Show the working
  1. A = a²
  2. Area = 144 ft²

Triangle (base and height)

Enter the base and height.

The base.
The perpendicular height.
The unit of every measurement; the answer is then also given in other units.
Result
Area of the triangle
30 ft²

The area of the triangle is 30 ft².

In other units
AmountUnit
2.7870912m²
27,870.912cm²
30ft²
4,320in²
3.333333333yd²
0.0006887052342acres
Show the working
  1. A = ½ × b × h
  2. Area = 30 ft²

Triangle (three sides)

Enter the side a, side b and side c.

First side.
Second side.
Third side.
The unit of every measurement; the answer is then also given in other units.
Result
Area of the triangle
666.5852815 ft²
Perimeter
125 ft

The area of the triangle is 666.5852815 ft².

In other units
AmountUnit
61.92779907m²
619,277.9907cm²
666.5852815ft²
95,988.28053in²
74.06503128yd²
0.01530269241acres
Show the working
  1. s = (a + b + c) ÷ 2 = 62.5
  2. A = √(s(s − a)(s − b)(s − c)) (Heron's formula)
  3. Area = 666.5852815 ft²

Triangle (two sides and the angle between)

Enter the side a, side b and angle.

First side.
Second side.
The angle, in the unit chosen below.
Degrees or radians.
The unit of every measurement; the answer is then also given in other units.
Result
Area of the triangle
26.47986102 ft²
Third side
6.666344593 ft
Perimeter
25.66634459 ft

The area of the triangle is 26.47986102 ft².

In other units
AmountUnit
2.460059587m²
24,600.59587cm²
26.47986102ft²
3,813.099987in²
2.94220678yd²
0.0006078939628acres
Show the working
  1. A = ½ × a × b × sin C, with C = 37°
  2. Area = 26.47986102 ft²

Circle

Enter the radius.

From the centre to the edge.
The unit of every measurement; the answer is then also given in other units.
Result
Area of the circle
2,827.433388 ft²
Exact
900π ft²
Diameter
60 ft
Circumference
188.4955592 ft (60π)

The area of the circle is 2,827.433388 ft² (900π ft²).

In other units
AmountUnit
262.6771572m²
2,626,771.572cm²
2,827.433388ft²
407,150.4079in²
314.1592654yd²
0.06490893913acres
Show the working
  1. A = π r²
  2. Area = 2,827.433388 ft²

Ellipse (oval)

Enter the semi-axis a and semi-axis b.

Half the width (horizontal).
Half the height (vertical).
The unit of every measurement; the answer is then also given in other units.
Result
Area of the ellipse
1,884.955592 ft²
Exact
600π ft²
Circumference
158.6543959 ft

The area of the ellipse is 1,884.955592 ft² (600π ft²).

In other units
AmountUnit
175.1181048m²
1,751,181.048cm²
1,884.955592ft²
271,433.6053in²
209.4395102yd²
0.04327262609acres
Show the working
  1. A = π a b
  2. Area = 1,884.955592 ft²

Sector

Enter the radius and angle.

From the centre to the edge.
The angle, in the unit chosen below.
Degrees or radians.
The unit of every measurement; the answer is then also given in other units.
Result
Sector area
706.8583471 ft²
Exact
225π ft²
Arc length
47.1238898 ft (15π)
Chord length
42.42640687 ft
Radius
30 ft

The sector area is 706.8583471 ft² (225π ft²).

In other units
AmountUnit
65.66928929m²
656,692.8929cm²
706.8583471ft²
101,787.602in²
78.53981634yd²
0.01622723478acres
Show the working
  1. θ = 90°
  2. Sector area = ½ r² θ (θ in radians) = θ/360 × π r²
  3. Arc length = r θ
  4. Sector area = 706.8583471 ft²

Circular segment

Enter the radius and angle.

From the centre to the edge.
The angle, in the unit chosen below.
Degrees or radians.
The unit of every measurement; the answer is then also given in other units.
Result
Segment area
9.058607371 ft²
Arc length
10.47197551 ft (10π/3)
Chord length
10 ft
Height (sagitta)
1.339745962 ft

The segment area is 9.058607371 ft².

In other units
AmountUnit
0.8415721629m²
8,415.721629cm²
9.058607371ft²
1,304.439461in²
1.00651193yd²
0.0002079570104acres
Show the working
  1. θ = 60°
  2. Segment area = ½ r² (θ − sin θ), θ in radians
  3. Segment area = 9.058607371 ft²

Ring (annulus)

Enter the outer radius and inner radius.

Radius of the outer circle.
Radius of the hole.
The unit of every measurement; the answer is then also given in other units.
Result
Area of the ring (annulus)
201.0619298 ft²
Exact
64π ft²
Ring width
4 ft

The area of the ring (annulus) is 201.0619298 ft² (64π ft²).

In other units
AmountUnit
18.67926451m²
186,792.6451cm²
201.0619298ft²
28,952.9179in²
22.34021443yd²
0.004615746783acres
Show the working
  1. A = π (R² − r²)
  2. Area = 201.0619298 ft²

Trapezoid

Enter the base a, base b and height.

One of the parallel sides.
The other parallel side.
The perpendicular height.
The unit of every measurement; the answer is then also given in other units.
Result
Area of the trapezoid
750 ft²
Median (mid-segment)
37.5 ft

The area of the trapezoid is 750 ft².

In other units
AmountUnit
69.67728m²
696,772.8cm²
750ft²
108,000in²
83.33333333yd²
0.01721763086acres
Show the working
  1. A = (a + b) ÷ 2 × h
  2. Area = 750 ft²

Parallelogram

Enter the base and height.

The base.
The perpendicular height.
The unit of every measurement; the answer is then also given in other units.
Result
Area of the parallelogram
600 ft²

The area of the parallelogram is 600 ft².

In other units
AmountUnit
55.741824m²
557,418.24cm²
600ft²
86,400in²
66.66666667yd²
0.01377410468acres
Show the working
  1. A = b × h
  2. Area = 600 ft²

Rhombus (diagonals)

Enter the diagonal p and diagonal q.

One diagonal.
The other diagonal.
The unit of every measurement; the answer is then also given in other units.
Result
Area of the rhombus
120 ft²
Side
13 ft
Perimeter
52 ft
Angle α
45.2397299°
Angle β
134.7602701°

The area of the rhombus is 120 ft².

In other units
AmountUnit
11.1483648m²
111,483.648cm²
120ft²
17,280in²
13.33333333yd²
0.002754820937acres
Show the working
  1. A = p × q ÷ 2
  2. side = ½√(p² + q²)
  3. Area = 120 ft²

Kite (diagonals)

Enter the diagonal p and diagonal q.

One diagonal.
The other diagonal.
The unit of every measurement; the answer is then also given in other units.
Result
Area of the kite
120 ft²

The area of the kite is 120 ft².

In other units
AmountUnit
11.1483648m²
111,483.648cm²
120ft²
17,280in²
13.33333333yd²
0.002754820937acres
Show the working
  1. A = p × q ÷ 2
  2. Area = 120 ft²

Regular polygon

Enter the number of sides and side.

3 to 1,000.
The length of a side.
The unit of every measurement; the answer is then also given in other units.
Result
Area of the regular polygon
41.56921938 ft²
Side (a)
4 ft
Perimeter (P)
24 ft
Circumradius (R)
4 ft
Inradius (r)
3.464101615 ft
Long diagonal (d)
8 ft
Short diagonal (s)
6.92820323 ft
Interior angle
120°

The area of the regular polygon is 41.56921938 ft².

In other units
AmountUnit
3.861906851m²
38,619.06851cm²
41.56921938ft²
5,985.967591in²
4.618802154yd²
0.0009542979657acres
Show the working
  1. From the side (a): side a = 4
  2. Area = n a² ÷ (4 tan(180° ÷ n)) = 6 × 4² ÷ (4 tan(30°))
  3. Area (A) = 41.56921938 ft²

Irregular quadrilateral

Enter the diagonal, height h₁ and height h₂.

Corner to opposite corner.
Height of the first triangle above the diagonal.
Height of the second triangle below the diagonal.
The unit of every measurement; the answer is then also given in other units.
Result
Area of the quadrilateral
140 ft²

The area of the quadrilateral is 140 ft².

In other units
AmountUnit
13.0064256m²
130,064.256cm²
140ft²
20,160in²
15.55555556yd²
0.00321395776acres
Show the working
  1. A = ½ × d × (h₁ + h₂), where h₁ and h₂ are the heights of the two triangles on the diagonal d
  2. Area = 140 ft²

Rectangular border (frame)

Enter the outer length, outer width, inner length and inner width.

Of the outer rectangle.
Of the outer rectangle.
Of the hole.
Of the hole.
The unit of every measurement; the answer is then also given in other units.
Result
Border area
128 ft²
Outer area
320 ft²
Inner area
192 ft²

The border area is 128 ft².

In other units
AmountUnit
11.89158912m²
118,915.8912cm²
128ft²
18,432in²
14.22222222yd²
0.002938475666acres
Show the working
  1. A = outer length × outer width − inner length × inner width
  2. Border area = 128 ft²

How to use it

Enter the length and width. Enter the side. Enter the base and height. Enter the side a, side b and side c. Enter the side a, side b and angle. Enter the radius. Enter the semi-axis a and semi-axis b. Enter the radius and angle. Enter the radius and angle. Enter the outer radius and inner radius. Enter the base a, base b and height. Enter the base and height. Enter the diagonal p and diagonal q. Enter the diagonal p and diagonal q. Enter the number of sides and side. Enter the diagonal, height h₁ and height h₂. Enter the outer length, outer width, inner length and inner width.

Enter the measurements (decimals, fractions such as 3/4, or mixed numbers such as 1 1/2) and, if you like, their unit; the answer is then also given in other units. Show the working gives the formula.

Key facts

Rectangle A = l w; triangle A = ½ b h; circle A = π r²; trapezoid A = ½ (a + b) h; ellipse A = π a b

Units of area

Area is measured in square units: a rectangle 30 ft by 20 ft has an area of 600 ft². Choose a unit to see the area in square meters, acres and more.

Questions

How do I find the area of a circle?

Multiply π by the radius squared: a radius of 30 ft gives 900π ≈ 2,827.433388 ft².

What is Heron's formula?

The area of a triangle from its three sides: √(s(s − a)(s − b)(s − c)), where s is half the perimeter.

Reviewed by RK Calculator Team. Updated 2026-09-26.

Formulas

Rectangle A = l w; triangle A = ½ b h; circle A = π r²; trapezoid A = ½ (a + b) h; ellipse A = π a b

Sources

Limitations

  • All measurements in one calculation use the same unit; the answer is also given in other units.
  • Measurements up to 10¹⁵.

Formula version 0.1.0Reviewed