Area of a Semicircle Calculator
The area of a semicircle is half a circle, A = πr² ÷ 2: a radius of 5 cm gives 39.2699 cm².
39.2699081698724 cm²
Full answer, then cut to fewer decimals (not rounded):
- 39.2699081698724 cm²
- 39.269908169872 cm²
- 39.26990816987 cm²
- 39.2699081698 cm²
- 39.269908169 cm²
- 39.26990816 cm²
- 39.2699081 cm²
- 39.269908 cm²
- 39.26990 cm²
- 39.2699 cm²
- 39.269 cm²
- 39.26 cm²
- 39.2 cm²
- Area
- 39.2699 cm²
- Arc length
- 15.708 cm
- Perimeter (arc + diameter)
- 25.708 cm
In other units: 0.00392699 m² · 3926.99 mm² · 3.92699 × 10⁻⁹ km² · 3.92699 × 10⁻⁷ ha · 0.0422698 ft² · 6.08685 in² · 0.00469664 yd² · 9.70381 × 10⁻⁷ ac · 1.51622 × 10⁻⁹ mi²
Step-by-step solution
- A = π r² ÷ 2
- A = π × 5² ÷ 2 = 39.2699 cm²
Area of a Semicircle Formula
A = π r² ÷ 2 = π d² ÷ 8
r radius, d diameter
Worked Example
A semicircle with a 5 cm radius:
- A = π r² ÷ 2
- A = π × 5² ÷ 2 = 39.2699 cm²
Arc length: 15.708 cm · Perimeter (arc + diameter): 25.708 cm
Same area in other units: 0.00392699 m² · 3926.99 mm² · 3.92699 × 10⁻⁹ km² · 3.92699 × 10⁻⁷ ha · 0.0422698 ft²
Frequently asked questions
What is the area of a semicircle of diameter d?
A = πd² ÷ 8. A 10 cm diameter gives 39.27 cm².
What is the perimeter of a semicircle?
The curved arc plus the diameter: P = πr + 2r. For r = 5 cm that is 25.71 cm.
How do I find the area of a quarter circle?
A = πr² ÷ 4, half of a semicircle.
Sources
- The International System of Units (SI), 9th edition (SI Brochure), Bureau International des Poids et Mesures .
- Guide for the Use of the International System of Units (SI), NIST Special Publication 811, 2008 Edition, National Institute of Standards and Technology .
Last reviewed: . Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.
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APA
Scientific Converters. (2026, October 15). Area of a Semicircle Calculator. Retrieved October 25, 2026, from https://scientificconverters.com/calculators/area-of-a-semicircle/
IEEE
Scientific Converters, "Area of a Semicircle Calculator," scientificconverters.com. Accessed: Oct. 25, 2026. [Online]. Available: https://scientificconverters.com/calculators/area-of-a-semicircle/