Semicircle Calculator
Calculate semicircle area, perimeter and diameter.
How to Use the Semicircle Calculator
Enter the radius or diameter requested by the tool to calculate semicircle area, curved length and perimeter.
Practical Example
For radius 5, the semicircle area is about 39.27 square units.
Factors That Affect the Result
Perimeter includes both the curved half-circumference and the straight diameter. Make sure you know whether the input is radius or diameter.
Frequently Asked Questions
Is semicircle perimeter half a circle’s circumference?
No. It also includes the diameter.
How is area calculated?
Use one half of πr².
Can I use diameter?
Yes, if the tool accepts it or after dividing by two for radius.
Related Tools
Working with a Semicircle
A semicircle has half the area of a full circle, so area is ½πr². Its curved edge is half the circumference, πr, but total perimeter also includes the straight diameter, giving πr + 2r.
Be clear about whether a task asks for curved arc length or the entire boundary. If diameter is measured, divide by two before using radius-based formulas. Keep units consistent and distinguish square units for area from linear units for perimeter.
Understanding Semicircle Calculations
A semicircle is half of a full circle. Its area is ½πr², while its total perimeter includes both the curved half-circumference and the straight diameter. This distinction matters because using only half of a circle’s circumference will understate the boundary length.
Enter radius and diameter values carefully: diameter is twice the radius. Keep the input unit consistent, and remember that area is reported in square units while perimeter and diameter remain in linear units.