A semicircle is exactly half of a circle. Its area is half the circle area, while its perimeter includes both the curved half-circumference and the straight diameter.
⚠Radius must be positive. Area is in square units, while perimeter is in the original length unit.
How Semicircle Area Works
Start with the full circle area πr² and divide by two. For perimeter, add the curved arc length to the diameter across the flat side.
Radius
Distance from center to curved edge.
Half Circle
Area is half of πr².
Diameter
The flat side is 2r.
Perimeter
Arc length plus diameter.
💡 Example: For r=6, A=(1/2)π(6²)=56.549 and perimeter=π(6)+12=30.85.
Applications of Semicircle Area
ArchesWindow DesignLandscapingGeometry Worksheets
Frequently Asked Questions
What is a semicircle area calculator?▼
It calculates the area of half a circle from the radius.
What is the semicircle area formula?▼
The formula is A = (1/2)πr², where r is the radius.
How do I use this calculator?▼
Enter the radius and click Calculate to get semicircle area and perimeter.
What is semicircle perimeter?▼
Semicircle perimeter includes the curved arc plus the diameter, so P = πr + 2r.
Where is semicircle area used?▼
It is used in windows, arches, landscaping, geometry worksheets, and design layouts.
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