🔲 Crop Factor & Equivalent Focal Length Calculator
Pick a sensor and enter a lens to get its crop factor and the full-frame-equivalent focal length and aperture.
Crop factor
1.53×
Equiv. focal length
54 mm
Equiv. aperture (DoF)
f/2.8
Crop factor = 43.3 mm (full-frame diagonal) ÷ your sensor's diagonal. Multiply your lens's focal length by it for the full-frame-equivalent field of view. The equivalent aperture (× crop) matches the depth of field and total light — but not the exposure, which the crop doesn't change. 🔒 In your browser.
How the crop factor & equivalent focal length calculator works
The crop factor is the full-frame diagonal (43.3mm) divided by your sensor's diagonal — a smaller sensor has a bigger crop factor. Multiply your lens's focal length by it for the equivalent full-frame field of view, and (for depth-of-field and total-light comparison) multiply the aperture by it too.
Equivalent aperture is about matching depth of field and background blur across formats — it does not change exposure. An f/1.8 lens still exposes as f/1.8 on any sensor; only its blur behaves like a larger f-number on a smaller sensor. So a 50mm f/1.8 on Micro Four Thirds frames and blurs like a 100mm f/3.6 on full frame.
Frequently asked questions
What is crop factor?
The ratio of a full-frame sensor's diagonal to your sensor's, showing how much a smaller sensor "crops" the view. APS-C is about 1.5–1.6×, Micro Four Thirds 2×. Multiply focal length by it for the full-frame-equivalent framing.
What is equivalent focal length?
The focal length that would give the same field of view on full frame. A 35mm lens on a 1.5× APS-C body has a 52.5mm equivalent — it frames like a 52.5mm lens does on full frame.
Does crop factor affect aperture and exposure?
It affects depth of field and total light gathered (the "equivalent aperture"), but not exposure. An f/2.8 lens meters and exposes as f/2.8 on every sensor — you don't change your settings for crop.
What is equivalent aperture?
The f-number × crop factor — used only to compare depth of field and background blur between formats. A 25mm f/1.4 on MFT (2× crop) gives the same framing and blur as a 50mm f/2.8 on full frame, though it still exposes at f/1.4.
Why do smaller sensors have more depth of field?
To get the same field of view you use a shorter lens (or stand closer), and shorter lenses have more depth of field at the same aperture. That's captured by the equivalent aperture being a higher number on smaller sensors.
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From the blog
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Crop Factor Explained: Your 50mm Doesn't Become a 75mm (and f/1.8 Is Still f/1.8)
Crop factor is the ratio between your sensor and 35mm film. It changes framing, not the lens. Here's why a 50mm on APS-C frames like a 75mm, why exposure never changes, and the one place the aperture multiplication is real.
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How to Blur the Background: The 4 Keys to Depth of Field
That creamy blurred background comes from a shallow depth of field — and four things control it: aperture, focal length, subject distance and sensor size. How each one works, and the exact recipe for a blurry background or front-to-back sharpness.