Focal Length Needed Calculator
Choose a lens by working backwards from the frame you want. Enter how far you stand from the subject, how tall the subject is, and your camera's sensor height, and see the focal length that fills the frame.
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- Works offline after your first visit
- Saves on this device
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- Updated
How it works
Divide the distance by the subject's height, then multiply by the sensor height. The result is the focal length in millimetres that makes the subject fill the frame's height.
The sensor height is a fixed figure for each camera. Full-frame sensors are about 24 mm tall. This is a simple estimate that works best when you stand well back, and it ignores lens distortion.
Worked example
Standing 30 ft from a subject 6 ft tall, with a 24 mm sensor, you need a lens of about 120 mm to fill the frame.
Questions
What sensor height should I enter?
Look up your camera's sensor size. A full-frame sensor is taller than an APS-C sensor, so the same lens frames less of the scene on the smaller one.
Why is the answer only an estimate?
It treats the lens as a simple lens and ignores close focusing. Close subjects need more care, so test the framing with your own lens.
Does the subject have to fill the whole height?
No. Subjects often look best with some space around them, so a shorter or longer lens may suit your own composition better.
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