Area Calculator

Print

Select shape and enter measurements

How many digits after decimal for displayed area (0–12).

Results

Choose a shape and enter measurements, then press Calculate.

Formulas & guidance

This page provides formulas, worked results and measurement tips for reliable area calculations. Use consistent units for inputs; the displayed area is in square units corresponding to the unit selector.

Common area formulas

  • Rectangle: area = width × height.
  • Square: area = side².
  • Triangle (base × height): area = 0.5 × base × height.
  • Triangle (Heron): s = (a+b+c)/2, area = √(s(s−a)(s−b)(s−c)).
  • Circle: area = π × r² (if diameter used r = d/2).
  • Trapezoid: area = 0.5 × (a + b) × height.
  • Parallelogram: area = base × height.
  • Ellipse: area = π × a × b (a and b are semi-axes).
  • Regular polygon: area = (n × s²) / (4 × tan(π/n)).
  • Annulus: area = π × (R² − r²).