March 26, 20264 min read

Focal Length Equivalent Calculator — Compare Lenses Across Sensor Sizes

Convert focal lengths between full frame, APS-C, Micro Four Thirds, and medium format. Understand crop factor and find your equivalent field of view.

focal length crop factor photography lens calchub

Someone recommends a "classic 50mm" for portraits, but you're shooting on an APS-C crop sensor. Is 50mm still the right choice, or do you need something different? That's exactly what the focal length equivalent calculator solves.

Try it now at CalcHub — enter your focal length and sensor size, get your full-frame equivalent instantly.

What Crop Factor Does

Smaller sensors don't see as wide a field of view as full frame. They "crop into" the image circle that the lens projects. This effective narrowing is described by the crop factor — a multiplier you apply to get the full-frame equivalent focal length.

APS-C sensors (Canon) have a crop factor of ~1.6x. APS-C (Nikon/Sony/Fuji) is ~1.5x. Micro Four Thirds is 2x. Medium format goes the other direction — less than 1x, meaning wider effective field of view.

How to Use the Calculator

Select your sensor format (or enter a custom crop factor)
Enter the actual focal length printed on your lens
Get the full-frame equivalent focal length

You can also work backwards — enter the equivalent you want (say, 85mm portrait look) and find what actual focal length achieves it on your sensor.

Equivalent Focal Lengths Across Systems

Actual Focal Length	APS-C (1.5x)	APS-C Canon (1.6x)	MFT (2x)
17mm	25.5mm eq.	27mm eq.	34mm eq.
24mm	36mm eq.	38mm eq.	48mm eq.
35mm	52.5mm eq.	56mm eq.	70mm eq.
50mm	75mm eq.	80mm eq.	100mm eq.
85mm	127mm eq.	136mm eq.	170mm eq.

So if you want a classic 50mm field of view on APS-C, you'd reach for a 35mm lens. A 85mm portrait lens equivalent needs a 56mm on APS-C Nikon or a 42.5mm on Micro Four Thirds.

It's Field of View, Not Depth of Field

This is where people get confused: crop factor changes how the scene is framed, but it doesn't change the actual aperture or the physics of the lens. A 50mm f/1.8 on APS-C gives the field of view of 75mm, but the depth of field of a 50mm f/1.8. It does NOT behave like a 75mm f/1.8 in terms of background blur.

For equivalent DoF, you'd also need to adjust aperture. Getting the full 75mm f/1.8 look on APS-C would require a ~50mm f/1.2 lens.

Practical Shooting Considerations

Crop sensors are excellent for telephoto reach. A 300mm lens on APS-C hits 450mm equivalent — great for wildlife and sports without paying for a 400mm prime. Wide angle is where crop sensors make life harder; you need wider glass to achieve the same field of view.

Does crop factor affect image quality?

Not directly — it affects framing. Image quality depends on the lens and the sensor's resolution and noise performance. A well-designed APS-C lens on APS-C can outperform a full-frame lens on full-frame if the optics are better.

What's the crop factor of smartphone cameras?

Most smartphones have sensors dramatically smaller than APS-C — often 1/2.3" or similar. Effective crop factors can be 5x–7x or higher. That's why a "24mm equivalent" lens on a phone is actually a tiny 4mm physical lens.

Do vintage lenses behave differently on crop sensors?

Yes, in terms of field of view only. A vintage 50mm f/1.4 on a modern APS-C camera frames like a 75mm. The glass itself still performs as it always did — the crop factor just changes how much of the image circle you use.

Depth of Field Calculator — see how sensor size affects DoF
Print Size Calculator — check if your megapixels support large prints
Exposure Calculator — balance your triangle on any system