Lens Focal Length Calculator
Use the similar-triangle relationship between sensor size, subject size, working distance and focal length.
Choose sensor dimension along the framing direction (vertical for subject height).
Calculated value
A QUICK WALKTHROUGH
How to use this tool
- Choose the one value to solve and enter the other three.
- Select a sensor preset or enter its dimension in millimeters.
- Calculate the framing estimate and compare it with available lenses.
Sensor dimension matters
The selected sensor value is the dimension along the framing direction (for example, vertical sensor height for subject height). The result is the actual focal length for that sensor, not a full-frame equivalent.
A framing estimate
The similar-triangle model does not account for focus breathing, lens distortion, internal focusing, or exact subject depth. It estimates framing; camera position determines perspective.
GOOD TO KNOW
Common questions
Does this convert to full-frame equivalent?
No. It calculates the actual focal length from the sensor dimension you select.
Can I solve for distance instead?
Yes. Choose any one of focal length, subject size, shooting distance, or sensor dimension to solve.