How do I calculate focal length from working distance and coverage?

Enter the sensor size, working distance, and required coverage width into the Calculate by Coverage mode. The calculator determines the required viewing geometry and estimates the focal length.

Industrial Lens Selection Tool

Focal Length Calculator

Calculate the required camera lens focal length based on sensor size, field of view, working distance, and required coverage. Find matching TOWIN industrial lenses for your imaging application.

Calculate the Right Focal Length

Choose a calculation method based on the information you already know about your camera and imaging scene.

Sensor Size Select the camera sensor format used by your imaging system.

Enter the actual sensor dimensions

Sensor Width

Sensor Height

Working Distance

Distance from the lens to the target object.

Required Coverage Width

The horizontal width of the area that must be captured.

Application (Optional) Optionally narrow the lens recommendations by application.

Recommended Focal Length

—

Theoretical focal length based on your input parameters

Horizontal FOV —

Sensor —

Working Distance —

Coverage Width —

Important: The calculated focal length is a theoretical value based on ideal geometric optics. Actual lens performance may vary due to optical design, distortion, sensor position, working distance, and mechanical tolerances. Use the result as a starting point for lens selection.

Matching TOWIN Lenses

Based on your calculated focal length, sensor size, field of view, and application, the following TOWIN lenses are the closest matches in our lens database.

How to Use the Focal Length Calculator

This Focal Length Calculator provides two calculation methods for different industrial imaging scenarios. Choose the method that matches the information available for your camera and application.

Select Sensor Size

Select the sensor format of your camera, or enter custom sensor dimensions if your sensor is not listed.

Choose a Method

Use Calculate by Coverage when you know the working distance and required viewing width, or Calculate by FOV when the required horizontal FOV is already known.

Calculate Focal Length

The calculator determines the theoretical focal length required for your imaging geometry.

Review Matching Lenses

Compare the calculated result with matching TOWIN industrial lenses from the lens database.

Which Focal Length Calculation Method Should You Use?

Industrial lens selection often starts with the physical imaging requirements of the application. If you know how far the camera is from the target and how wide an area needs to be captured, the Coverage method is usually the most practical starting point.

Calculation Method	Required Inputs	Best For	Result
Calculate by Coverage	Sensor Size + Working Distance + Coverage Width	Industrial vision and real-world imaging scenes	Focal Length + FOV
Calculate by FOV	Sensor Size + Horizontal FOV	Systems with a predefined viewing angle	Focal Length

Focal Length Calculation Formula

The calculator uses the sensor width and the required imaging geometry to estimate the focal length. The calculation differs depending on the selected method.

Calculate by Coverage

When the working distance and required coverage width are known, focal length can be estimated from the sensor width and imaging distance.

f = (S × WD) / W

f = focal length, S = sensor width, WD = working distance, W = required coverage width.

Calculate by FOV

When the horizontal field of view is already known, the required focal length can be estimated directly from the sensor width.

f = S / [2 × tan(FOV / 2)]

f = focal length, S = sensor width, and FOV = horizontal field of view.

What Factors Affect Focal Length Selection?

Focal length should not be selected independently from the camera, sensor, and imaging environment. Several optical and mechanical parameters should be considered when choosing an industrial lens.

Sensor Size: The sensor determines the image area used to calculate the required focal length and field of view.
Working Distance: The distance between the lens and target affects the coverage area and required focal length.
Required Coverage: The width or height of the target area determines how much of the scene must be captured.
Field of View: A wider FOV generally requires a shorter focal length, while a narrower FOV generally requires a longer focal length.
Resolution: The lens should provide sufficient optical resolution for the camera sensor and application requirements.
Distortion: Low-distortion lenses are particularly important when dimensional measurement, machine vision inspection, or accurate object positioning is required.
Mount: The lens mount must be mechanically compatible with the camera, such as M12, C-Mount, CS-Mount, or another supported interface.

Frequently Asked Questions

A focal length calculator estimates the lens focal length required for a specific camera sensor and imaging geometry. Depending on the calculation method, it can use field of view, working distance, and required coverage to determine a suitable focal length.

Enter the sensor size and required horizontal field of view into the Calculate by FOV mode. The calculator uses the sensor width and viewing angle to estimate the required focal length.

Enter the sensor size, working distance, and required coverage width into the Calculate by Coverage mode. The calculator first determines the required viewing geometry and then estimates the focal length.

Yes. For the same field of view, a larger sensor generally requires a longer focal length than a smaller sensor. Sensor size should therefore be considered together with FOV when selecting a lens.

There is no single focal length that is best for every machine vision application. The appropriate focal length depends on sensor size, working distance, required field of view, target coverage, resolution, and distortion requirements.

Yes. After calculating the theoretical focal length, the calculator compares the result with the TOWIN lens database and displays lenses with similar focal length, sensor compatibility, FOV, and optional application matching.

The result is a starting point for lens selection rather than a guaranteed final specification. Optical distortion, mechanical tolerances, sensor position, aperture, resolution, and the actual lens design can affect real-world performance. Final lens selection should be verified against the complete optical requirements of the application.

Yes. Select Custom Sensor and enter the actual sensor width and height. The calculator will use the custom sensor width for the horizontal focal length calculation.

Need Help Selecting an Industrial Lens?

If the calculated focal length does not provide a suitable match, TOWIN can help evaluate sensor compatibility, FOV, distortion, resolution, mount type, and application requirements for your project.

Request a Lens Solution