Background blur calculator

F-stop The focal length divided by the aperture size. I.e. : 1.4 for aperture "f/1.4"
Focal length mm The actual focal length of the lens, without any factors applied. Most lenses have this printed on them somewhere.
Sensor Width mm A measure of the size of the sensor inside the camera.
Sensor Aspect Ratio Width/Height Ratio. 1.5 for 24x36 argentic and most DSLRs, 1.3333 for (compact) digital cameras
Pixel Count MPixels How many MegaPixels in the senseor.
Lens to subject m The distance between the lens and the object being photographed.
Subject to background m The distance that the background is behind the subject.
Crop % The amount the image is cropped. 100% indicates no cropping. 50% indicates that the image is half the full height.

Results

(press Tab)

or change any parameter to compute
One metre subject size % How much of the final image a one metre subject will fill.
Pixels per line pixels .
Pixel Width microns .
Background blur % The size a point in the background will be projected onto the sensor divided by the diagonal of the sensor.
Pixels blur pixels The number of pixels a point in the background will be projected onto.

Based on initial version of calculator on robertseber.com