Focal Length Calculator – Calculate Lens Focal Length

🔍 Focal Length Calculator

Calculate lens focal length using object and image distances

🎯 Calculation Results

🔍 How to Use the Focal Length Calculator

  1. Enter the object distance (distance from object to lens)
  2. Enter the image distance (distance from lens to image)
  3. Select the appropriate units for each distance
  4. Click “Calculate” to find the focal length

📐 What is Focal Length?

  • Distance between the lens and the focal point where parallel rays converge
  • Critical parameter in optics for image formation and magnification
  • Used in cameras, microscopes, telescopes, and corrective glasses
  • Determines the lens’s ability to converge or diverge light rays

🧮 The Lens Formula

Thin Lens Equation:

1/f = 1/do + 1/di

Where: f = focal length, do = object distance, di = image distance