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

Low Distortion 2.7mm M12 Lens

CIL027-F2.8-M12A650

Low Distortion 2.7mm M12 Lens

Large Format 3.5mm M12 Lens

CIL334-F2.2-M12C660

Large Format 3.5mm M12 Lens

195°@4.7mm Fisheye M12 Lens

CIL216-F2.2-M12ANIR

195°@4.7mm Fisheye M12 Lens

200°@5.7mm IP67 Fisheye M12 Lens

CIL217-F2.7-M12A650

200°@5.7mm IP67 Fisheye M12 Lens

226°@3.9mm Fisheye M12 Lens

CIL212-F2.2-M12A660

226°@3.9mm Fisheye M12 Lens

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

230 degree M12 Fisheye lens
230 degree M12 Fisheye lens
Ultra-wide fisheye lens with 230 degree field of view
230degree mini fisheye lens
CIL213-F2.3-M12A660
230°@4.5mm Fisheye M12 Lens
$129.00
AR0822 M12 Lens CIL358
AR0822 M12 Lens CIL358
6mm Wide Angle Lens CIL358
OX08B40 Lens
CIL358-F1.9-M12A650
Wide-Angle 5.8mm M12 Lens
$49.00
A 2.8mm M12 lens with a wide angle and no distortion for the RPi HQ Camera.
A 2.8mm M12 lens with a wide angle and no distortion for the RPi HQ Camera.
A 2.8mm M12 lens with a wide angle and no distortion for the RPi HQ Camera.
A 2.8mm M12 lens with a wide angle and no distortion for the RPi HQ Camera.
CIL028-F2.3-M12A650
Low Distortion 2.6mm M12 Lens
$39.00
3mm Mini Fisheye M12 Lens
3mm Mini Fisheye M12 Lens
3mm S Mount Fisheye Lens Raspberry Pi
Miniature Fisheye Lens
CIL231-F1.9-M12A650
190°@9.1mm Fisheye M12 Lens
$99.00
3.5mm Wide-Angle M12 Lens
3.5mm Wide-Angle M12 Lens
3.5mm Wide-Angle S-Mount Lens
Wide-Angle M12 Lens CIL335
CIL335-F1.8-M12A660
Wide-Angle 3.5mm M12 Lens
$49.00
Short Compact 3.6mm M12 Lens CIL036
Short Compact 3.6mm M12 Lens CIL036
Compact 3.6mm S Mount Lens CIL036
Compact 3.6mm M12 Lens CIL036
CIL036-F2.2-M12A650
Small 3.3mm M12 Lens
$19.00

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

200°@5.8mm Fisheye Lens

CIL273-F2.0-M12A650

200°@5.8mm Fisheye Lens

No Distortion 6mm M12 Lens

CIL062-F2.8-M12A650

No Distortion 6mm 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.

195°@4.7mm Fisheye M12 Lens

CIL216-F2.2-M12ANIR

195°@4.7mm Fisheye M12 Lens

IR Corrected 4.4mm M12 Lens

CIL046-F2.0-M12A650

IR Corrected 4.4mm M12 Lens

190°@4.2mm IR Corrected M12 Fisheye

CIL215-F2.0-M12ANIR

190°@4.2mm IR Corrected M12 Fisheye

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.

Large Format 3.5mm M12 Lens

CIL334-F2.2-M12C660

Large Format 3.5mm M12 Lens

185°@7.8mm Fisheye M12 Lens

CIL227-F2.5-M12B660

185°@7.8mm Fisheye M12 Lens

Small 2.1mm M12 Lens

CIL821-F2.4-M12ANIR

Small 2.1mm M12 Lens

200°@5.7mm IP67 Fisheye M12 Lens

CIL217-F2.7-M12A650

200°@5.7mm IP67 Fisheye M12 Lens

190°@6.8mm Fisheye M12 Lens

CIL282-F1.8-M12B660

190°@6.8mm Fisheye M12 Lens

185°@7.8mm Fisheye M12 Lens

CIL227-F2.5-M12B660

185°@7.8mm Fisheye M12 Lens

Exposed to the Elements?

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.

200°@6.3mm Fisheye M12 Lens

CIL219-F2.5-M12A650

200°@6.3mm Fisheye M12 Lens

Low Distortion 7.2mm M12 Lens

CIL872-F2.8-M12A650

Low Distortion 7.2mm M12 Lens