Calculate diameter, radius (straal), circumference and area of a circle instantly. Diameter cirkel berekenen made easy.
A circle calculator is an essential online tool for students, engineers, architects, and anyone working with circular shapes. Whether you need to calculate the diameter cirkel, find the straal van een cirkel (radius), or compute the area and circumference, our free online rekenmachine handles it all instantly.
The straal (radius) is the distance from the center of a circle to its edge. Here are the formulas to calculate the radius:
Example: If the diameter cirkel is 14 cm, then the straal = 14 ÷ 2 = 7 cm.
The diameter is the longest chord of a circle — it passes through the center and connects two points on the edge. To calculate the diameter cirkel:
| Property | Formula | Dutch Term |
|---|---|---|
| Radius | r = d / 2 | Straal |
| Diameter | d = 2r | Middellijn |
| Circumference | C = 2πr = πd | Omtrek |
| Area | A = πr² | Oppervlakte |
Pi (π) is a mathematical constant approximately equal to 3.14159265358979. It represents the ratio of a circle's circumference to its diameter. Pi is the same for every circle, regardless of size — this makes it a universal constant used in all circle calculations.
A circle is a 2D shape — it has a radius, diameter, circumference, and area. A sphere is the 3D version — it has a radius, diameter, surface area, and volume. Our calculator handles 2D circle calculations (straal van een cirkel, diameter cirkel berekenen).
Hoe bereken je de straal van een cirkel? Deel de diameter door 2: straal = diameter ÷ 2.
What is the relationship between diameter and radius? The diameter is always exactly twice the radius: d = 2r, and r = d/2.
Can I calculate the area if I only know the circumference? Yes — first find radius: r = C/(2π), then area: A = πr².
What units does this calculator use? The calculator works with any unit (cm, mm, m, inches, feet). Just make sure your input and output are in the same unit.