Square Inches of a Circle Calculator
Calculate the area of a circle in square inches using radius, diameter, or circumference
Calculate Circle Area in Square Inches
Distance from center to edge of the circle
Circle Area Results
Example Calculations
3 cm Radius Circle
Given: Radius = 3 cm
Convert to inches: 3 cm ÷ 2.54 = 1.181 inches
Area: A = π × 1.181² = π × 1.394 = 4.38 square inches
6 inch Diameter Circle
Given: Diameter = 6 inches
Radius: r = 6 ÷ 2 = 3 inches
Area: A = π × 3² = π × 9 = 28.27 square inches
Construction Example
Circular duct: 8 inch diameter
Cross-sectional area: π × (8÷2)² = π × 16 = 50.27 sq in
Used for: HVAC calculations and material estimates
Unit Conversions to Inches
Circle Formulas
Area
A = π × r²
Or A = π × d²/4
Circumference
C = 2 × π × r
Or C = π × d
Radius
r = d/2
Or r = C/(2π)
Construction Uses
HVAC duct cross-sectional area
Pipe and conduit sizing
Round window and door openings
Circular carpet and flooring
Material quantity estimates
Understanding Square Inches of a Circle
What is Square Inches?
Square inches of a circle is the area of a circle expressed in square inches, an imperial unit commonly used in the United States, construction industry, and various engineering applications. It represents the total space enclosed within the circle's boundary.
Why Use Square Inches?
- •Standard unit in US construction industry
- •Easy communication with contractors and suppliers
- •Material specifications and calculations
- •HVAC and mechanical engineering applications
Calculation Steps
Step 1: Determine Radius
Find or measure the radius of the circle
Step 2: Convert to Inches
Convert the radius to inches using conversion factors
Step 3: Apply Formula
Area = π × radius² to get square inches
Pro Tip: For construction projects, always double-check your unit conversions and add a small buffer (5-10%) for material waste and cutting allowances.