Crop Factor Calculator
Our crop factor calculator lets you know what your camera and lens combination looks like in terms of a 35 mm full-frame sensor. It calculates both the 35 mm-equivalent focal length and the equivalent aperture f-stop value (or f-number), so you can see how your image magnification and depth of field compare to a standard 35 mm camera.
The text below explains how to calculate the crop factor and answers the common question: does a crop sensor increase magnification?
What does 35 mm mean?
Let's start by defining what we mean by a 35 mm full-frame camera. It all began in 1934, when Kodak introduced the 135 film cartridge. The film inside was 35 mm (1.4 in) wide, and each image was 36 by 24 mm in size. This size became known as the full-frame format.
As photography went digital and manufacturers replaced film with digital optical sensors, it was convenient to keep producing sensor sizes matching the old film — at least for high-end cameras. This compatibility let you keep using your existing lenses on a new digital camera and get the same image.
What is a crop sensor camera?
Producing such a large image sensor is expensive. You can obviously save money by making a smaller sensor. However, if you still use your old 35 mm lenses, the magnification and aperture f-stop of those lenses are altered — and so is the depth of field.
So, if your camera has a sensor smaller than a full-frame camera, it is called a crop sensor camera. We use the word "crop" because the smaller sensor's resulting image is a cropped version of the larger full-frame image. In other words, it changes the field of view of the camera.
How to calculate crop factor?
The crop factor compares the image sensor size to the full-frame sensor size. To account for different aspect ratios, it is defined as the ratio of the diagonal length of the 35 mm sensor to that of the crop sensor:
crop factor = diagonalfull-frame ÷ diagonalcrop sensor
The full-frame diagonal is √(36² + 24²) = 43.27 mm. For example, a typical APS-C sensor of 23.6 × 15.7 mm has a diagonal of √(23.6² + 15.7²) ≈ 28.34 mm, giving a crop factor of 43.27 ÷ 28.34 ≈ 1.53×.
How to use the crop factor calculator?
- Pick your sensor size from the list (Full Frame, APS-C, Micro Four Thirds, 1-inch and more), or choose Custom and type the sensor width and height.
- Enter the focal length of your lens (as written on the barrel, e.g. 50 mm).
- Optionally enter the aperture (f-number) of your lens to see the equivalent f-stop.
- The calculator instantly returns your crop factor, the 35 mm-equivalent focal length, and the equivalent aperture.
Switch between the metric (mm) and American (inches) systems at any time — the results are always shown in both.
Does a crop sensor increase magnification?
Not really — a crop sensor does not magnify the image; it crops it. Because the sensor captures a smaller portion of the image the lens projects, the subject appears larger in the final framed photo, mimicking a longer lens. That is why a 300 mm lens on a 1.5× crop body frames like a 450 mm lens on full frame. The apparent "reach" increases, but the actual optical magnification of the lens is unchanged.
What happens to the depth of field? — F-stop settings
To match the framing of a full-frame camera you use a shorter actual focal length on a crop body — and shorter focal lengths give more depth of field at the same f-number. Multiplying the f-number by the crop factor gives the equivalent aperture: the f-stop a full-frame camera would need to reproduce the same depth of field (and total light gathered) as your crop-sensor setup.
For example, an f/2.8 lens on a 1.5× crop sensor behaves — in terms of depth of field and total light — like an f/4.2 lens on full frame. This is why full-frame cameras are prized for their shallow, blurred backgrounds.
Common crop factors at a glance
| Sensor | Dimensions | Crop factor |
|---|---|---|
| Medium Format (44×33) | 43.8 × 32.9 mm | 0.79× |
| Full Frame (35mm) | 36 × 24 mm | 1.0× |
| APS-H (Canon) | 28.7 × 19.0 mm | 1.25× |
| APS-C (Nikon / Sony / Fuji) | 23.6 × 15.7 mm | 1.53× |
| APS-C (Canon) | 22.3 × 14.9 mm | 1.61× |
| Micro Four Thirds | 17.3 × 13.0 mm | 2.0× |
| 1-inch (CX) | 13.2 × 8.8 mm | 2.72× |
| 1/2.3-inch | 6.17 × 4.55 mm | 5.64× |
Frequently Asked Questions
What is the crop factor of an APS-C camera?
It depends on the brand. Canon APS-C sensors have a crop factor of about 1.6×, while Nikon, Sony, Fujifilm and Pentax APS-C sensors are about 1.5×, because their sensors are slightly larger.
Does crop factor change the actual focal length of my lens?
No. A 50 mm lens is always a 50 mm lens. The crop factor only tells you the equivalent focal length — the full-frame lens that would give the same field of view on a full-frame camera.
Does crop factor affect exposure or shutter speed?
No. The f-number that controls exposure (shutter speed / ISO) is unchanged — an f/2.8 lens still exposes as f/2.8. The equivalent f-number only describes depth of field and the total amount of light collected across the whole sensor.
Is a smaller crop factor better?
A crop factor closer to 1.0 (or below, for medium format) means a larger sensor, which generally gathers more light and offers shallower depth of field. Smaller sensors (larger crop factors) are cheaper, lighter, and give more apparent telephoto reach, which many wildlife and sports shooters value.