What is crop factor and how is it calculated?

Crop factor is the full-frame 35mm diagonal (43.27 mm) divided by the sensor's diagonal. An APS-C sensor at roughly 28.4 mm diagonal gives a crop factor near 1.5×, meaning a 50mm lens frames like a 75mm lens on full frame.

Why does sensor area matter more than megapixels?

A larger sensor area collects more total light at the same exposure, which directly improves dynamic range and high-ISO noise. Doubling the sensor area gathers about twice the light, which is why full frame outperforms a 1-inch sensor at the same megapixel count.

Is full frame exactly twice the area of APS-C?

Not exactly. Full frame (864 mm²) is roughly 2.3× the area of a Sony/Nikon APS-C sensor (around 370 mm²) and about 2.6× a Canon APS-C sensor. The exact ratio depends on which APS-C variant you compare, which is why the tool lets you set the baseline.

Does crop factor change the aperture?

Crop factor changes the equivalent depth of field and total light gathered, not the f-number printed on the lens. An f/2.8 lens stays f/2.8 for exposure, but on a 2× crop sensor it gives depth of field and total-light behaviour closer to f/5.6 on full frame.

What sensor is in a typical smartphone?

Most smartphone main cameras use sensors between 1/2.3" (about 28 mm²) and 1" (about 116 mm²). Even a 1-inch phone sensor has roughly one-seventh the area of full frame, which is the main reason dedicated cameras still pull ahead in low light.

Camera Sensor Size Comparison Tool

This tool puts every common camera sensor format on the same scale so you can see exactly how much bigger a full-frame sensor is than APS-C, Micro Four Thirds or a smartphone sensor. It reports the physical dimensions, diagonal, crop factor and the relative light-gathering area that ultimately drives image quality.

How it works

Every sensor is defined by its physical width and height in millimetres. From those two numbers the tool derives three quantities.

Diagonal is the Pythagorean length of the sensor:

diagonal = sqrt(width² + height²)

Crop factor compares that diagonal to the 35mm full-frame reference (36 × 24 mm, a diagonal of 43.27 mm):

crop factor = 43.27 / sensor diagonal

A crop factor of 1.5 means any lens frames 1.5× tighter than it would on full frame, so a 35mm lens behaves like a 52mm lens. Area is simply width × height, and the relative-area column divides each sensor’s area by your chosen baseline.

Why area is the number that matters

Two sensors can share the same megapixel count yet deliver very different images. The larger sensor spreads those pixels over more silicon, so each pixel — or the sensor as a whole — collects more photons at the same exposure. More photons means a cleaner signal-to-noise ratio, which translates into better high-ISO performance and wider dynamic range. Doubling sensor area gives roughly a one-stop noise advantage.

Tips and notes

Crop factor multiplies focal length for framing, but it does not change the f-number for exposure. A 50mm f/1.8 lens stays f/1.8 for metering on any sensor.
For equivalent depth of field and total light, multiply both focal length and f-number by the crop factor: 50mm f/1.8 on Micro Four Thirds (2× crop) looks like 100mm f/3.6 on full frame.
Medium-format figures here use the common 44 × 33 mm “cropped” medium format found in mirrorless bodies, not the larger 53 × 40 mm of some digital backs.