Question 1

What is the formula for the area of a circle?

Accepted Answer

The area of a circle is A = π × r², where r is the radius. For example, a circle with radius 5 has area π × 25 ≈ 78.54 square units.

Question 2

What is the formula for the circumference of a circle?

Accepted Answer

The circumference is C = 2π × r, or equivalently C = π × d where d is the diameter. A circle with radius 5 has circumference 10π ≈ 31.42 units.

Question 3

What is the difference between radius and diameter?

Accepted Answer

The radius is the distance from the center of the circle to its edge. The diameter is the distance across the circle through the center, equal to 2 × radius.

Question 4

What is a sector and segment of a circle?

Accepted Answer

A sector is the pie-slice region bounded by two radii and an arc. A segment is the region bounded by a chord and the arc it cuts off. Both are calculated using the central angle in radians or degrees.

Question 5

Can I use this calculator with different units?

Accepted Answer

Yes. Enter any unit (mm, cm, m, km, in, ft, yd, mi) and the calculator returns the same unit for length, and that unit squared for area. Results are also shown in alternative units for convenience.

📐 Basic properties

🥧 Sector / Arc / Segment