What the focal length calculator does
The same lens gives a different view on different cameras, because sensors differ in size. A 50 mm lens on a full-frame camera shows a normal perspective; on an APS-C body it frames like a 75 or 80 mm, and on Micro Four Thirds like a 100 mm. This calculator converts a lens's focal length to its full-frame equivalent for a chosen sensor (crop factor), so you can compare lenses across systems, understand what “equivalent” means in reviews, and choose the right lens for the field of view you want. Runs in your browser.
The formula
Equivalent focal length = actual focal length × crop factor
Crop factor = full-frame diagonal (43.3 mm) ÷ sensor diagonal
50 mm on APS-C (1.5×) → 75 mm equivalent
50 mm on Canon APS-C (1.6×) → 80 mm equivalent
50 mm on Micro Four Thirds (2.0×) → 100 mm equivalentCommon sensor formats
| Format | Sensor size (mm) | Crop factor | Used by |
|---|---|---|---|
| Full frame (35 mm) | 36 × 24 | 1.0× | Canon R/5D, Nikon Z/D, Sony A7, Leica M, Panasonic S |
| APS-C (Nikon, Sony, Fujifilm, Pentax) | 23.5 × 15.6 | 1.5× | Nikon Z50/D7500, Sony A6000 series, Fujifilm X |
| APS-C (Canon) | 22.3 × 14.9 | 1.6× | Canon R7/R10/R50, EOS 90D |
| Micro Four Thirds | 17.3 × 13 | 2.0× | OM System, Panasonic G/GH |
| 1-inch | 13.2 × 8.8 | 2.7× | Sony RX100, many compacts, drones |
| Medium format (44 × 33) | 43.8 × 32.9 | 0.79× | Fujifilm GFX, Hasselblad X |
| Typical phone main camera | ≈ 9.8 × 7.3 | ≈ 4.4× | iPhone, Pixel, Galaxy (varies) |
Field of view by equivalent focal length
| Equivalent | Horizontal angle | Character |
|---|---|---|
| 14 mm | 104° | Ultra-wide — architecture, astro, cramped interiors |
| 24 mm | 74° | Wide — landscapes, environmental portraits, phones' main camera |
| 35 mm | 54° | Classic reportage; close to natural perception |
| 50 mm | 40° | 'Normal' — everyday, street, portraits with context |
| 85 mm | 24° | Portrait — flattering compression |
| 135 mm | 15° | Tight portrait, stage |
| 200 mm | 10° | Sport, wildlife at moderate distance |
| 400 mm | 5° | Birds, distant wildlife, field sports |
What the crop factor does not change
- The lens itself. A 50 mm lens is always 50 mm; the smaller sensor just records the centre of its image. Perspective from a given position is identical.
- Aperture for exposure. f/2.8 lets in the same light per area on any sensor. Exposure settings do not change.
- Depth of field at the same framing does change: to frame a subject the same way, a crop-sensor shooter stands further back or uses a shorter lens, which increases depth of field. Multiply the f-number by the crop factor for the “equivalent” depth of field — f/2.8 on APS-C looks like f/4.2 on full frame.
- Low-light performance is largely a function of sensor area; the same crop factor squared is a fair guide to the noise difference at equal settings.
Common uses
- Choosing a lens for a crop body to match a look you know from full frame (a 35 mm on APS-C for a “50 mm” view).
- Reading reviews and spec sheets that quote “35 mm equivalent”.
- Comparing phone cameras (26 mm equivalent main, 13 mm ultra-wide, 77 mm telephoto) with real lenses.
- Planning how far to stand for a given framing when switching bodies.
- Working out effective reach for wildlife — a 300 mm on APS-C frames like 450 mm.
Frequently asked questions
Is a longer equivalent focal length 'free reach'?
It is the same as cropping a full-frame image — you get the framing, but with the smaller sensor's pixel count and noise. Real reach comes from a longer lens.
Why is Canon's crop factor different from Nikon's?
Canon's APS-C sensors are slightly smaller (22.3 mm wide vs 23.5), giving 1.6× instead of 1.5×.
Does a full-frame lens work on a crop body?
Yes — it projects a larger image circle than needed and the sensor uses the centre. A crop-format lens on a full-frame body usually vignettes or triggers crop mode.
What is the equivalent aperture?
Multiply the f-number by the crop factor to compare depth of field and total light gathered. It does not change the exposure settings you dial in.
How do I convert a phone camera's specs?
Phones already quote equivalent focal lengths (e.g. 24 mm); the physical lens is only a few millimetres. Use the equivalent figure directly.
Are my values stored?
No. The calculation runs in your browser.