Crop Factor Equivalent Focal Length Calculator
See what focal length your lens really behaves like on a crop sensor — plus the equivalent aperture for depth of field.
How it works
Equivalent focal length = focal length × crop factor · Equivalent aperture = f-number × crop factor
A smaller sensor captures only the middle of the image a full-frame sensor would see, so the field of view looks like a longer lens. Multiplying the physical focal length by the sensor’s crop factor gives the full-frame-equivalent focal length that produces the same framing. The same crop factor also applies to aperture when you care about depth of field: an f/1.8 lens on APS-C renders background blur like f/2.7 on full frame, even though it still gathers f/1.8 worth of light for exposure.
Worked example
A 50 mm f/1.8 lens on an APS-C Nikon body (1.5× crop) frames like a 50 × 1.5 = 75 mm lens, with depth of field like f/1.8 × 1.5 = f/2.7 on full frame.
Frequently asked questions
Does crop factor change the exposure?
No. The equivalent aperture applies only to framing and depth of field. For exposure the lens is still f/1.8, so shutter speed and ISO are set from the real aperture, not the equivalent one.
Which crop factor should I use?
Pick the sensor that matches your camera. Canon APS-C is about 1.6×, most other APS-C bodies are 1.5×, Micro Four Thirds is 2.0×, and 1-inch compacts are about 2.7×. Full frame is 1.0× by definition.
Is equivalent focal length a real optical change?
No — the lens itself is unchanged. Crop factor only describes how the smaller sensor’s narrower view compares with full frame, so a 50 mm lens is always a 50 mm lens optically.
Related calculators
This calculator is for educational purposes. Double-check important results before acting on them.