Camera Lens Effective Focal Length Calculator (EFL Calculator)

Focal Length Calculator.webp__PID:b5ddb454-486a-4633-a5f9-5eab9cd96b87
A Camera Focal Length Calculator. This Calculates a Lens EFL for Cameras.

What is Effective Focal Length (EFL)?

The focal length of a lens is the distance from its principal plane to the sensor when the lens is focused at infinity. It sets how “zoomed-in” your camera is, much like resistor value sets current in a circuit. The focal length requirement for your camera is also dependent on the image sensor size.

Engineers often talk about effective focal length (EFL) because real lenses have multiple glass elements and principal planes that don’t sit at the mechanical mount. EFL gives you a single number that still predicts field of view (FoV) exactly. Think of it as the optical “equivalent resistance” of a lens stack.

Field of view shrinks as focal length grows and expands as the sensor gets larger. Horizontal, vertical, and diagonal FoV each use the matching sensor dimension. An online EFL calculator saves you from manual trigonometry: enter sensor width, desired FoV, and it solves for focal length in millimeters.

Most tools assume the lens is focused at infinity, which is valid for robotics and machine-vision ranges beyond a few metres. If you work at macro distances, refocus and recalculate because EFL shifts slightly with object distance.

Distortion Impacts the Calculation. Real-world design rarely stops at EFL. Wide-angle lenses introduce barrel distortion which changes the FoV and EFL calculation. Check datasheets for distortion plots and ensure BFL + shim thickness equals your sensor flange depth.When selecting a lens, start with your required FoV, plug it into the calculator, and pick the nearest catalog lens that covers your sensor format.

Read Our Camera Calculator & Optics Design Page, or Click below Use our Other Camera Calculators

Camera Field of View Calculator. FoV Calculator
Camera Depth of Field Calculator. DoF Calculator.
Camera Angle of View Calculator for Camera Lens Selection. AoV Calculator.

Here are a Few M12 Lenses. Search all 50+ Using Our M12 Lens Calculator

215°@6.8mm M12 Fisheye Lens

CIL220-F2.3-M12BNIR

215°@6.8mm M12 Fisheye Lens

190°@6.4mm Fisheye M12 Lens

CIL281-F1.8-M12ANIR

190°@6.4mm Fisheye M12 Lens

Wide-Angle 4mm M12 Lens

CIL339-F1.6-M12B640

Wide-Angle 4mm M12 Lens

No Distortion 3.2mm M12 Lens

CIL034-F2.3-M12A660

No Distortion 3.2mm M12 Lens

No Distortion 6mm M12 Lens

CIL062-F2.8-M12A650

No Distortion 6mm M12 Lens

We Also have Cost Effective 12MP+ C-Mount Lenses for Machine Vision and Factory Automation.

180°@14.2mm C-Mount Fisheye Lens

CIL505-F2.2-CMANIR

180°@14.2mm C-Mount Fisheye Lens

8mm C-Mount Lens 1.1" 12MP

CIL508-F2.4-CMANIR

8mm C-Mount Lens 1.1" 12MP

12mm C-Mount Lens 1.1" 12MP

CIL512-F2.8-CMANIR

12mm C-Mount Lens 1.1" 12MP

16mm C-Mount Lens 1.1" 12MP

CIL513-F2.8-CMANIR

16mm C-Mount Lens 1.1" 12MP

25mm C-Mount Lens 1.1" 12MP

CIL514-F2.8-CMANIR

25mm C-Mount Lens 1.1" 12MP
215 degree Miniature Fisheye Lens CIL220
215 degree Miniature Fisheye Lens CIL220
M12 Mini Fisheye Lens
Miniature Fisheye Lens
CIL220-F2.3-M12BNIR
215°@6.8mm M12 Fisheye Lens
$39.00
High resolution M12 Fisheye lens
High resolution M12 Fisheye lens
S-Mount Fisheye Lenses
Embedded Camera Fisheye Lenses
CIL281-F1.8-M12ANIR
190°@6.4mm Fisheye M12 Lens
$59.00
Wide-Angle 4mm M12 Lens
Wide-Angle 4mm M12 Lens
Wide-Angle 4mm M12 Lens
CIL339-F1.6-M12B640
Wide-Angle 4mm M12 Lens
$109.00
Basler Dart Camera IP67 M12 Lens
Basler Dart Camera IP67 M12 Lens
3mm M12 Lens
FLIR Camera S-Mount Lens M12 Lens
CIL034-F2.3-M12A660
No Distortion 3.2mm M12 Lens
$39.00
6mm M12 Lens
6mm M12 Lens
Raspberry Pi 6mm Lens
6mm S-Mount Lens
CIL062-F2.8-M12A650
No Distortion 6mm M12 Lens
$19.00
IR Corrected 12mm M12 Lens
IR Corrected 12mm M12 Lens
12mm S-Mount Lens
IR Corrected M12 Lens
CIL122-F2.0-M12A650
IR Corrected 12mm M12 Lens
$59.00

What's Your Application? Our Lenses Cover the Spectrum.

215°@6.8mm M12 Fisheye Lens

CIL220-F2.3-M12BNIR

215°@6.8mm M12 Fisheye Lens

Low Distortion 2.2mm M12 Lens

CIL023-F2.2-M12B650

Low Distortion 2.2mm M12 Lens

Mobile Robotics?

Find a low F# or low distortion lens to optimize your computer vision.

Factory Machine Vision?

Our cost-effective compact C-Mount lenses are designed for up to 1.1"~1.2" format global shutter sensors.

180°@14.2mm C-Mount Fisheye Lens

CIL505-F2.2-CMANIR

180°@14.2mm C-Mount Fisheye Lens

8mm C-Mount Lens 1.1" 12MP

CIL508-F2.4-CMANIR

8mm C-Mount Lens 1.1" 12MP

No Distortion 3.2mm M12 Lens

CIL034-F2.3-M12A660

No Distortion 3.2mm M12 Lens

Low Distortion 2.7mm M12 Lens

CIL027-F2.8-M12A650

Low Distortion 2.7mm M12 Lens

Intelligent Everywhere?

Our low distortion lenses with multiple F# can be used to optimize your depth of field.

Surveillance?

Our fisheye and IR Corrected lenses are suitable for doorbell cameras and active IR illuminated scenes.

190°@5.7mm Fisheye M12 Lens

CIL290-F2.2-M12A660

190°@5.7mm Fisheye M12 Lens

IR Corrected 4.4mm M12 Lens

CIL046-F2.0-M12A650

IR Corrected 4.4mm M12 Lens

200°@4.5mm MiniFisheye M12 Lens

CIL914-F2.4-M12B650

200°@4.5mm MiniFisheye M12 Lens

195°@5.2mm Fisheye Lens

CIL818-F2.0-M12A660

195°@5.2mm Fisheye Lens

Does it Require Getting Dirty?

Our IP67 and IP69K lenses are suitable for applications exposed to the environment.

Aerial Robotics?

Our tiny lenses are ideal for collision avoidance and object recognition.

195°@5.2mm Fisheye Lens

CIL818-F2.0-M12A660

195°@5.2mm Fisheye Lens

Small 2.1mm M12 Lens

CIL821-F2.4-M12ANIR

Small 2.1mm M12 Lens