The Focal Length vs Sensor Size Calculator helps photographers and videographers determine how a lens will behave on different camera sensor sizes. A lens acts differently on a full-frame camera compared to a crop sensor camera. This tool shows you the effective focal length and field of view (FOV) when switching between camera bodies.
This calculator belongs to the Photography / Camera Lens Tools category. It’s especially useful for:
- Comparing gear
- Planning a shoot
- Understanding lens behavior before buying
Whether you're shooting landscapes, portraits, or wildlife, knowing the crop factor helps you choose the right lens for your needs.
Formula of Focal Length Vs Sensor Size Calculator
1. Crop Factor Formula
Crop Factor = Diagonal of Full-Frame Sensor / Diagonal of Your Camera Sensor
Where:
- Full-frame diagonal = √(36² + 24²) = ≈ 43.27 mm
- Your sensor diagonal = √(width² + height²)
2. Equivalent Focal Length Formula
To match the field of view between different cameras:
Equivalent Focal Length = Actual Focal Length × Crop Factor
Or, to compare between sensors:
Equivalent Focal Length on Sensor B = Focal Length × (Crop Factor B / Crop Factor A)
These formulas help convert between formats like APS-C, Micro Four Thirds, and Full Frame.
Sensor Size Reference Table
| Sensor Type | Dimensions (mm) | Diagonal (mm) | Crop Factor |
|---|---|---|---|
| Full Frame (35mm) | 36.0 × 24.0 | 43.27 | 1.0 |
| APS-C (Canon) | 22.3 × 14.9 | ≈ 26.82 | ≈ 1.6 |
| APS-C (Nikon/Sony) | 23.6 × 15.6 | ≈ 28.21 | ≈ 1.5 |
| Micro Four Thirds | 17.3 × 13.0 | ≈ 21.64 | ≈ 2.0 |
| 1-inch Sensor | 13.2 × 8.8 | ≈ 15.86 | ≈ 2.7 |
These values help you instantly reference how much a lens's effective reach changes across different systems.
Commonly Searched Terms Table
| Term | Description |
|---|---|
| Focal Length | Distance from the lens’s optical center to the sensor (in mm) |
| Crop Factor | Ratio used to adjust focal length based on sensor size |
| Full Frame | 35mm sensor size (standard in professional cameras) |
| APS-C | Crop sensor format with approx. 1.5–1.6x crop factor |
| Equivalent Focal Length | The apparent focal length after accounting for the crop factor |
| Field of View (FOV) | How much of the scene the lens captures; changes with sensor size |
| Diagonal Measurement | Used to calculate sensor size and crop factor |
| Telephoto Effect | Longer focal length or high crop factor narrows the field of view |
| Wide Angle | Shorter focal length results in a wider view |
| Image Circle | The diameter of the image a lens projects onto the sensor |
Example of Focal Length Vs Sensor Size Calculator
Let’s say you have a 50mm lens and want to know how it performs on an APS-C Canon camera (crop factor ≈ 1.6):
Step 1:
Use the formula:
Equivalent Focal Length = 50 × 1.6 = 80 mm
Result:
On an APS-C Canon camera, the 50mm lens gives the same field of view as an 80mm lens on a full-frame body. It behaves more like a short telephoto, ideal for portraits.
Most Common FAQs
No, it doesn't change the physical focal length of the lens. It only changes how the image is framed or cropped based on the sensor size.
Not always. Larger sensors give better low-light performance and shallower depth of field, but smaller sensors are more compact and affordable.
Because a smaller sensor only captures the center part of the image circle projected by the lens. This creates a "zoomed-in" effect, reducing the field of view.