Crop Factor Calculator

What it does

Converts a focal length on one sensor format to the focal length that produces the same field of view on a different format — most commonly used to find a lens's “full-frame-equivalent” focal length, but works between any two formats in the list.

What you'll need

• The focal length you're converting.
• The sensor format that focal length is actually on.
• The sensor format you want the equivalent for.

Steps

1. Enter the focal length.
2. Pick the format it's actually on.
3. Pick the format you want the equivalent focal length for.

Reading the result

The result is the focal length that would frame the same field of view on the second format. It's a field-of-view equivalence only — it says nothing about depth of field, which follows separate rules (see the DoF Calculator) and doesn't scale the same way as field of view does across formats.

Tips

• Set both formats to the same value to confirm the calculator returns your original focal length unchanged — a quick sanity check.
• For the exact angle in degrees rather than an equivalent focal length, use the Field of View Calculator instead.

What is crop factor?

Crop factor is a ratio comparing a sensor's size to a full-frame sensor (36×24mm), used as a quick way to describe how much narrower a smaller sensor's field of view is at the same focal length. A crop factor of 1.6×, for instance, means a lens on that sensor frames roughly like a lens 1.6 times longer would on full-frame — not because the lens itself changes, but because the smaller sensor only captures the central, narrower portion of the same image circle.

Why photographers use it

Photographers who've built intuition for focal lengths on one sensor format — most commonly full-frame — can use crop factor to translate that intuition to a different camera. Knowing that your APS-C camera's 35mm lens frames roughly like a 56mm lens would on full-frame lets you reuse decades of “how a 50mm normal lens looks” experience without needing to relearn framing from scratch on a new body.

Common mistakes

• Assuming crop factor changes the actual focal length. it doesn't — a 50mm lens is still physically a 50mm lens on any camera. Crop factor only describes how much of that lens's projected image the smaller sensor actually captures, changing the field of view, not the lens's real optical properties.
• Applying crop factor to depth of field the same way as field of view. field of view scales directly with crop factor, but depth of field doesn't follow the same simple multiplication — use the DoF Calculator with the correct sensor format selected instead of trying to convert a DoF result by crop factor.
• Forgetting crop factor changes effective aperture for exposure comparisons across formats. some photographers also compare an "equivalent aperture" across formats for depth-of-field comparison purposes — that's a separate, more debated convention from the field-of-view equivalence this calculator handles, and the two shouldn't be conflated.

Example settings

FAQ

Does crop factor make a lens "better" or "worse"?

Neither — it's purely a framing difference. A crop sensor's narrower field of view can be useful (extra reach for wildlife/sports) or limiting (harder to go wide), depending entirely on what you're shooting.

Why is full-frame's crop factor listed as 1.0?

Because it's the reference point every other format's crop factor is defined against — a crop factor of 1.0 means "no crop relative to itself."

Does this affect my aperture setting too?

No — the f-number you set on your lens doesn't change with sensor format. Some photographers separately discuss an "equivalent aperture" for cross-format depth-of-field comparison, but that's a different, more debated convention from the field-of-view conversion this tool performs.