Updated Geometry

Area Calculator

Find the area of common 2D shapes, advanced triangle and circle measures, 3D surface areas, and composite regions in one place.

2D Shapes Triangles Circles 3D Surface Area

All-in-One Area Calculator

Switch between 2D shapes, triangle methods, circle measures, 3D surface area, and composite regions.

Units are generic; if you enter meters, the result is in square meters, etc.

For the two-sides-and-angle method, the angle must be the angle between the two sides.

If radius is zero or empty, the calculator will use diameter to derive the radius.

Volume is also shown to give more context for 3D shapes.

This treats the shape as a big rectangle with a smaller rectangular hole removed (for example, a room with a cut-out section).

Area Calculator – 2D Shapes, 3D Surface Area & Composite Regions

This Area Calculator helps you quickly find the area of common 2D shapes, advanced triangle and circle configurations, 3D surface areas, and composite rectangular regions. Enter your dimensions in any unit and the result will be in squared or squared-derived units for that system.

Basic 2D Area Formulas

  • Rectangle: A = length × width
  • Square: A = side²
  • Circle: A = πr²
  • Triangle (base and height): A = ½bh
  • Trapezoid: A = ½(a + b)h
  • Parallelogram: A = base × height

Triangle Area Methods

The triangle tab supports multiple ways to calculate area:

  • Base and height: A = ½bh
  • Three sides (Heron’s formula): s = (a + b + c) ÷ 2, A = √[s(s − a)(s − b)(s − c)]
  • Two sides and included angle C: A = ½ab sin(C) (with C in degrees)

Circle, Arc Length, and Sector Area

For a circle with radius r:

  • Area: A = πr²
  • Circumference: C = 2πr

For a central angle θ in degrees:

  • Arc length: L = (θ ÷ 360) × 2πr
  • Sector area: A = (θ ÷ 360) × πr²

3D Surface Area Formulas

  • Cube (side s): Surface area = 6s², Volume = s³
  • Rectangular prism (l, w, h): Surface area = 2(lw + lh + wh), Volume = lwh
  • Cylinder (radius r, height h): Surface area = 2πr² + 2πrh, Volume = πr²h
  • Sphere (radius r): Surface area = 4πr², Volume = 4⁄3 πr³
  • Right circular cone (radius r, height h): with slant height ℓ = √(r² + h²), Surface area = πr² + πrℓ, Volume = ⅓πr²h

Composite Rectangular Regions

Many real-life floor plans or plots are combinations of rectangles. One common approach is to model an L-shaped region as a big rectangle minus a smaller cut-out rectangle:

Composite area = Outer area − Inner cutout area

Use this calculator to experiment with dimensions, compare shapes, and build geometric intuition. Try more free tools on MyTimeCalculator for fitness, finance, health, math, and science calculations.

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