Focal Length Calculator

Calculate focal length and field of view for camera lenses.

Scene Parameters

Distance to Object (m)

Object Width (m)

Sensor Format

Required Lens

Physical Focal Length72.0mm

To fill the sensor width

35mm Equivalent72.0mmField of view match

Crop Factor1x

This assumes a standard rectangular projection. For very wide lenses (fisheye), this linear formula does not apply.

Overview

Focal length determines lens magnification and field of view. Short focal lengths (wide-angle) capture more scene; long focal lengths (telephoto) magnify distant subjects. Essential for photography and optics.

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Pro Tips

Wide-angle: 14-35mm; Standard: 35-70mm; Telephoto: 70mm+.
50mm approximates human eye field of view on full-frame.
Crop sensors multiply effective focal length (1.5-1.6×).
Prime lenses (fixed focal length) often sharper than zooms.

Fun Facts

"Focal length measured in millimeters (mm)."
"Kit lenses typically 18-55mm (3× zoom range)."
"Super-telephoto: 400-800mm for wildlife/sports."
"Fisheye lenses: 8-15mm with 180°+ field of view."

Formula: FOV = 2 × arctan(Sensor Size / (2 × Focal Length))

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