Plane Geometry Calculators
Choose from our collection of free online geometry calculators to solve problems involving 2D shapes, areas, perimeters, and distances.
Basic Shapes
Circle Calculator
Calculate area, circumference, radius, and diameter given any one property.
Square Calculator
Find area, perimeter, and diagonal of a square given the side length.
Rectangle Calculator
Calculate area, perimeter, and diagonal given length and width.
Parallelogram Calculator
Find area given base and height of a parallelogram.
Triangles
Right Triangle Calculator
Use the Pythagorean theorem to find missing sides and calculate properties.
Equilateral Triangle Calculator
Calculate area, perimeter, and height given the side length.
Isosceles Triangle Calculator
Find properties given base and equal side lengths.
Triangle Theorems (Heron's)
Calculate area of any triangle using Heron's formula.
Advanced Shapes
Rhombus Calculator
Calculate area, side length, and perimeter given diagonal lengths.
Regular Polygon Calculator
Find area, perimeter, and apothem for any regular polygon.
Annulus Calculator
Calculate area of a ring shape given outer and inner radii.
Stadium Calculator
Find area and perimeter of a stadium/racetrack shape.
Distance & Triangle Laws
Distance Between Points
Calculate the straight-line distance between two points in 2D space.
Law of Cosines
Find unknown sides or angles in any triangle using c² = a² + b² - 2ab·cos(C).
Law of Sines
Calculate unknown triangle parts using a/sin(A) = b/sin(B) = c/sin(C).
Reference & Help
Geometric Shapes Reference
Complete list of formulas for all 2D shapes including areas, perimeters, and special properties.
How to Use These Calculators
Each calculator is designed to be simple and intuitive:
- Enter your known values in the input fields
- Click Calculate to get instant results
- View step-by-step solutions showing the formulas used
- Share your calculations using the provided link
All calculations are performed using standard mathematical formulas and provide results with high precision.