Lens & Focal Length Calculators
Calculate crop factors, equivalent focal lengths, field of view, magnification, extension tubes and more.
Crop Factor Calculator
Convert focal lengths between different sensor sizes using crop factor. Compare APS-C, Micro Four Thirds and full-frame equivalent fields of view. Free calculator.
Equivalent Focal Length Calculator
Find the full-frame equivalent focal length for any sensor size. Compare lenses across different camera systems with instant results. Free online calculator.
Field of View Calculator
Calculate horizontal, vertical and diagonal field of view for any lens and sensor combination. Plan shots and coverage before you shoot. Free calculator.
Magnification Calculator
Calculate optical magnification from focal length and subject distance. Determine image size on sensor for macro and close-up photography. Free online calculator.
Minimum Focus Distance Calculator
Find the working distance and maximum magnification at your lens minimum focus distance. Plan macro and close-up shots with precision. Free calculator.
Extension Tube Calculator
Calculate the added magnification and reduced focus distance when using extension tubes. Find the ideal tube length for your macro setup. Free calculator.
Teleconverter Calculator
Calculate effective focal length, maximum aperture and light loss when using teleconverters. Compare 1.4x and 2x extender results. Free online calculator.
Lens Compression Calculator
Visualise how perspective compression changes at different focal lengths and shooting distances. Understand background rendering for portraits. Free calculator.
Angle of View Calculator
Calculate the horizontal, vertical and diagonal angle of view for any lens and sensor combination. Useful for planning scene coverage. Free online calculator.
Close-Up Lens Calculator
Calculate magnification and effective focus range when using close-up dioptre filters. Find the right dioptre strength for your macro needs. Free calculator.
10 free calculators in Lens & Focal Length
Understanding Lenses and Focal Length
Focal length, measured in millimetres, determines the field of view and magnification of a lens. A shorter focal length (e.g. 24mm) gives a wider field of view, while a longer focal length (e.g. 200mm) narrows the view and magnifies distant subjects. On a full-frame (36×24mm) sensor, a 50mm lens is considered “normal” as it approximates human field of view.
Crop factor accounts for sensors smaller than full-frame. An APS-C sensor (crop factor 1.5x or 1.6x) makes a 50mm lens behave like a 75-80mm on full-frame in terms of field of view. Micro Four Thirds has a 2x crop factor. This affects not just framing but also the apparent depth of field and the minimum handheld shutter speed.
Extension tubes are hollow spacers placed between the camera body and lens to decrease the minimum focus distance and increase magnification. They do not contain optical elements, so image quality is unaffected, but you lose the ability to focus at infinity. The magnification gained depends on the tube length relative to the lens focal length.
Teleconverters (1.4x, 2x) multiply the focal length but also reduce the effective aperture. A 2x teleconverter on a 70-200mm f/2.8 gives 140-400mm f/5.6. Our calculators help you understand the trade-offs and plan your lens kit for any shooting situation.