The focal length calculator is a simple tool that facilitates the process of computing the **magnification, focal length**, and **the angle of view**.

Taking a picture of an object from a distance might be challenging – we’ll help you find the right focal length to create an image that perfectly **fits your cameras’ sensor size**.

In the article below, we’ll teach you how to find the focal length, discover the **lens equation**, and talk about a few essential **principles of photography** and the lens choice.

## What’s the focal length?

*Focal length* is one of the primary values of a photographic lens. Manufacturers usually give it in **millimeters (mm)**.

Focal length describes the distance between the rear principal point and the sensor – in other words, it’s the space starting **from the center of the lens, to the point where the light rays converge in the focal point** (to form a sharp picture on a surface of a digital sensor, or 35mm film).

focused at infinity. |

* angle of view* – this variable informs us of the amount of the scene that will be captured. The wider the angle,

**the more of the scene can be transferred to a sensor**, and be visible on the photograph. Thanks to the angle of view option, we don’t really need an additional

**field of view**calculator – we got everything ready!

*– it allows us to measure how the size of an object changes when transferred to photography.*

**magnification**

**Still hungry for knowledge?** Try our other lens calculators:

## How to use the focal length calculator?

Our lens equation calculator has a straightforward structure; **fill in at least three fields** in order to acquire results.

- Typical
:**image sizes**- 3.6, 4.8, 5.8, 6.4, 8.8, 12.8 mm,
- or 1/4, 1/3, 1/2.5, 1/2, 2/3, 1 inch.

(Hey, if you’re still not familiar with different units, try our length conversion tool

) is measured from the lens’s front principal plane to the object itself.**Object distance**

work both ways. Your result can simply become another query! |

The lens that makes objects appear small will have a **small magnification** – on the other hand, the lens that magnifies the picture will have a **big magnification**.

## How to calculate focal length?

Finding focal length is an easy and very much needed ability; follow our simple guide to **find all the details of these calculations**!

- The typical focal length formula looks as follows:
`1/Focal length = 1/Image distance + 1/Object distance`

,where:

**Image distance**and**Object distance**are given in mm.

- And here’s the transformed equation that we use:
`Focal length = (Object distance / ((1 / Magnification) + 1)) * 1000`

,where:

**Object distance**is given in mm; and**Magnification**does not have a unit.

- In order to copy the
**lens magnification calculator**, you’ll need the following equation (take a closer look – it may also serve as an**image distance formula**!):`Magnification = Image size / Object size = -(Image distance / Object Distance)`

,where:

**Object size**– is the real size of an object, given in mm; and**Image size**– is the size of the camera’s digital sensor or 35mm film, given in mm.

- To calculate the
**angle of view**, you need to use the most complex equation of them all:`Angle of view = (180/π) * 2 * aTan(Image size / (2 * Focal length * (Magnification + 1)))`

,where: