This circle calculator is best for the common situation where you know one circle measurement but need the rest. Sometimes you have the radius, but just as often you have a diameter from a drawing, a measured circumference, or an area from a geometry problem. The page converts that one known quantity into a full set of circle properties.
That makes it useful for geometry homework, quick engineering checks, fabrication planning, and layout review. In many real tasks, the problem is not forgetting the formulas. It is that the known value is not the one you actually need next. The page closes that gap quickly.
The page supports radius, diameter, circumference, and area. Choosing the correct starting quantity is the first step to avoiding conversion mistakes.
Enter one positive number. The unit is up to you as long as you stay consistent. All length-style outputs will remain in that same unit family. The important distinction is that area is not a linear unit. If radius is in centimeters, area is in square centimeters.
La page actuelle accepte le rayon, le diamètre, la circonférence ou l'aire comme valeur connue.
Oui. La page accepte la saisie de nombres décimaux ordinaires.
Parce qu'un cercle complet ne peut pas avoir un rayon, une circonférence ou une aire nuls ou négatifs.
Oui. Il recalcule dès que le mode ou la valeur change, et le bouton de calcul exécute explicitement la même logique.
Compute radius, diameter, circumference, and area from any one known circle measurement.