Solve radius, diameter, area, and circumference parameters
Circular Geometry Map
Calculations & Formulas
Evidence-based guide
Circles are defined by all points equidistant from a single center point. The relationship between radius, diameter, area, and circumference is governed by the mathematical constant Pi (π ≈ 3.14159).
Calculates diameter (2r), circumference (2πr), and area (πr²).
Calculates radius (d/2), circumference (πd), and area (π(d/2)²).
Calculates radius (√(A/π)), diameter (2r), and circumference (2√(πA)).
Calculates radius (c/(2π)), diameter (c/π), and area (c²/(4π)).
Entering any single parameter allows the solver to calculate the other three dimensions immediately using high-precision calculations.
The formulas apply to flat, 2D Euclidean spaces. In curved spaces (like spherical geometry), these relations do not hold.
Pi is an irrational mathematical constant representing the ratio of a circle's circumference to its diameter. It is roughly equal to 3.14159.
The radius is the distance from the center to the edge. The diameter is the distance from edge to edge passing through the center, which is exactly twice the radius.
Area is measured in square units (e.g. cm²) as it measures 2D space, while circumference is linear (e.g. cm) as it measures perimeter.
