🔲 Tube Surface Area Calculator 2026
Calculate inner, outer, end, and total surface areas of cylindrical tubes
Enter Tube Dimensions
R = outer, r = inner,
L = length
📊 Surface Area Results
Outer Surface
628.3 cm²
Inner Surface
502.7 cm²
End Rings (×2)
56.5 cm²
Total Surface
1,187.5 cm²
Wall Thickness
1 cm
Cross-Section
28.27 cm²
📝 Step-by-Step Solution
Given: R = 5 cm, r = 4 cm, L = 20 cm
Outer Surface = 2πRL = 2π × 5 × 20 = 628.32 cm²
Inner Surface = 2πrL = 2π × 4 × 20 = 502.65 cm²
End Rings = 2 × π(R² - r²) = 2π(25 - 16) = 56.55 cm²
Total = Outer + Inner + Ends = 1,187.52 cm²
📐 Tube Surface Area Formulas
Outer Curved Surface: Aout = 2πRL
Inner Curved Surface: Ain = 2πrL
End Ring Area (each): Aring = π(R² - r²)
Total Surface: Atotal = 2πRL + 2πrL + 2π(R² - r²)
Simplified: Atotal = 2π[RL + rL + R² - r²]
Understanding Tube Geometry
🔲 Tube Structure
Hollow cylinder with outer radius R and inner radius r. Has four distinct surface regions: outer curved, inner curved, and two ring-shaped ends.
📏 Outer Surface
A = 2πRL. Same as a solid cylinder. The external curved surface area. Used for exterior coating, painting.
⭕ Inner Surface
A = 2πrL. The inside curved surface. Important for fluid flow, lining, internal coating. Smaller than outer surface.
🔘 End Rings
A = π(R² - r²) each. The ring-shaped ends (annuli). Two of them. Combined: 2π(R² - r²).
Frequently Asked Questions
What is the total surface area of a tube?
A = 2πRL + 2πrL + 2π(R² - r²). Outer curved + inner curved + two
ring ends. All four surface regions combined.
What is the outer surface area of a tube?
A = 2πRL. Same formula as cylinder lateral surface. Outer radius
times length times 2π.
What is the inner surface area of a tube?
A = 2πrL. Uses inner radius. The curved surface inside the tube.
Important for flow calculations.
What is the end ring area?
A = π(R² - r²). Ring-shaped (annulus) area at each end. Total for
both ends: 2π(R² - r²).
How do I find wall thickness?
t = R - r. Outer radius minus inner radius. Can also be (D - d)/2
using diameters.
What is the cross-sectional area?
A = π(R² - r²). Same as one end ring. The ring-shaped
cross-section of the tube wall.
How is a tube different from a pipe?
Same geometry. "Tube" often implies structural use (exact OD),
"pipe" implies flow use (NPS sizing). Formulas are identical.
What if I only know diameters?
Divide by 2 to get radii. R = D/2, r = d/2. Then use standard
formulas.
How do I calculate paint for a tube?
Use relevant surfaces. Exterior only: 2πRL. Interior too: add
2πrL. Include ends if needed: +2π(R²-r²).
What is the volume of tube material?
V = π(R² - r²)L. Cross-section times length. Use for weight
calculations with density.
What is the inner capacity?
V = πr²L. Volume of the hollow space inside. Amount of fluid tube
can hold.
How does surface area change with wall thickness?
Thicker wall = larger difference in R and r. Outer stays same if R
fixed. Inner decreases, ends increase.
What are examples of tubes?
Pipes, straws, paper towel cores, toilet paper rolls, metal tubes,
hoses. Any hollow cylinder.
Can I use diameter instead of radius?
Yes, adjust formulas. Outer: πDL for outer surface. Inner: πdL.
Ends: (π/4)(D² - d²) each.
What is an annulus?
Ring-shaped region between two concentric circles. The tube end is
an annulus. Area = π(R² - r²).
How do I find inner radius from wall thickness?
r = R - t. Inner radius = outer radius minus wall thickness.
How accurate is this calculator?
Uses precise mathematical formulas with π to full precision.
Assumes perfect cylindrical tube.