Circle Calculator
Calculate area, circumference, radius and diameter of a circle. Step-by-step explanation, free and no registration required.
Result
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Formulas
Diameter: d = 2 * r
Circumference: U = 2 * Pi * r = Pi * d
Area: A = Pi * r²
Note: These calculations are for informational purposes only and do not replace professional tax or financial advice. All information without guarantee.
Frequently Asked Questions
How do I calculate the area of a circle?
Area equals pi times radius squared (A = pi times r squared). With a radius of 5 cm, the area is approximately 78.54 square centimeters.
How do I calculate the circumference of a circle?
Circumference equals 2 times pi times radius (or pi times diameter). With a diameter of 10 cm, the circumference is approximately 31.42 cm.
What is the Circle Calculator?
The circle calculator computes circumference, area, diameter and radius of a circle from one known value.
How does the Circle Calculator work?
Enter the radius, diameter, circumference or area. The calculator computes all other values: circumference = 2 * pi * r, area = pi * r squared. Additionally, circular segment and sector are calculated.
Key Data and Facts
Circumference = 2 * pi * r = pi * d. Area = pi * r squared. Pi approx. 3.14159. Sector area = (angle / 360) * pi * r squared.
Step-by-Step Guide
How to calculate Kreisgroessen step by step: 1. Eine bekannte Groesse enter: Radius (r), Durchmesser (d = 2r), Umfang (U) oder Flaeche (A). 2. Alle Groessen calculate: Umfang = 2 x pi x r = pi x d. Flaeche = pi x r2. Durchmesser = 2 x r. Radius = d / 2. 3. Vom Umfang zum Radius: r = U / (2 x pi). 4. Von der Flaeche zum Radius: r = Wurzel(A / pi). 5. Kreissektor (Tortenstueck) calculate: Bogenlaenge = (Winkel / 360) x 2 x pi x r. Sektorflaeche = (Winkel / 360) x pi x r2. 6. Kreisring calculate: Flaeche = pi x (R2 - r2), wobei R der Aussenradius und r der Innenradius ist. 7. Pi ≈ 3,14159265. Fuer Ueberschlagsrechnungen genuegt pi ≈ 3,14. Tipp: Der Umfang eines Kreises waechst linear mit dem Radius, die Flaeche quadratisch -- ein doppelter Radius bedeutet vierfache Flaeche.
Calculation Example
Radius 5 cm: Umfang = 2 x 3,14159 x 5 = 31,42 cm. Flaeche = 3,14159 x 25 = 78,54 cm2. Durchmesser = 10 cm.
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