Torus (Donut) Surface Area Calculator

Calculate external surface area A = 4 × π² × R × r of a torus from major radius R and minor tube radius r.

How It Works & Processing Standards

Enter values above to calculate results automatically. Check each input field for guidance and units.

Example: majorRadius=3, minorRadius=1 → 118.435253

Your input data is never sent to any server and is securely processed on your device.

Current Limits

  • Maximum input length: 100,000 characters

Torus (Donut) Surface Area Calculator is a 100% free, browser-based online utility. All calculations and file conversions run locally inside your browser (Local-First) without sending data to remote servers, keeping your documents and inputs strictly private.

How to Use Torus (Donut) Surface Area Calculator

  1. 1
    Enter Major Radius (R)Type center-to-tube-center radius.
  2. 2
    Enter Minor Radius (r)Type tube radius (r < R).
  3. 3
    View Surface AreaRead calculated torus surface area.

Common Use Cases

  • Calculating rubber coating area for toroidal O-ring seals
  • Estimating heat exchanger cooling pipe skin area in circular loops
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