Crop Factor Calculator

Frequently Asked Questions

Does crop factor change my exposure?

No. A lens set to f/1.8 meters as f/1.8 regardless of sensor size. Exposure is determined by aperture, shutter speed, and ISO. Crop only affects framing and depth of field.

Is a crop sensor always worse than full-frame?

Not necessarily. Crop sensors offer reach advantage for telephoto work, and modern APS-C and Micro Four Thirds sensors are excellent for most subjects. Full-frame wins in low light and maximum shallow depth of field.

What is the crop factor for a phone camera?

Phone sensors are tiny - roughly 1/1.7 inch - with crop factors around 5-7x depending on the model. Enter the sensor dimensions in the custom field for an accurate result.

Why does the calculator add a focal length field if crop factor is about sensor size?

Entering a focal length lets the tool immediately show you the 35 mm-equivalent focal length and the equivalent aperture, saving you the manual multiplication.

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Estimates for informational purposes only.

Important Disclaimer: Estimates for informational purposes only.

This calculator provides estimates for informational purposes only. Results are based on assumptions and may not reflect actual outcomes. Consult qualified professionals in relevant fields before making important decisions based on these results.

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How It Works

The crop factor (also called focal length multiplier) compares a sensor's diagonal to that of a full-frame 35mm sensor, which measures 36 x 24 mm and has a diagonal of approximately 43.27 mm. The formula is simply: crop factor = 43.27 / sensor diagonal.

From the crop factor we derive three useful equivalences. The 35mm-equivalent focal length is the actual focal length multiplied by the crop factor - it tells you how a lens frames compared to full-frame. A 50 mm lens on an APS-C body (crop 1.53) frames like a 76 mm lens on full-frame.

The equivalent aperture for depth of field is the f-number multiplied by the crop factor. An f/1.8 lens on APS-C gives the same depth of field and collects the same total light as roughly f/2.8 on full-frame. Note that the lens still meters as f/1.8 for exposure - only depth of field and total light gathered scale with crop.

Use Cases

Crop factor matters whenever you compare lenses or bodies across different sensor formats:

Planning framing when switching between a full-frame and APS-C body with the same lens

Understanding why wildlife and sports shooters love Micro Four Thirds - a 300 mm lens reaches like 600 mm

Comparing bokeh and background separation across systems

Choosing portrait lenses that replicate the 85 mm or 135 mm full-frame look on a crop sensor

Estimating noise and total-light differences between sensor sizes

Tips

The 35 mm equivalent focal length is a framing guide only - it does not change how the lens renders perspective.

Perspective compression depends on subject distance, not focal length. Moving farther back gives the same compression regardless of sensor size.

Canon APS-C (x1.6) and Nikon/Sony APS-C (x1.5) differ; always pick the correct preset to get an accurate result.

Use the equivalent aperture when comparing how blurred a background will look, but use the actual f-number when setting exposure.

The ISO factor output shows how much more ISO the crop sensor needs to match the full-frame body's total-light sensitivity at the equivalent aperture.

FAQ