License Plate Capture Calculator
Lens, scene width and shutter speed for reading plates at your lane width, distance and traffic speed.
Plate and traffic
75 px is the minimum to resolve characters; most LPR software wants 100 to 150
Keep the total angle under 30°
Camera
Results
Fix the highlighted values to see results.
Result
Max scene width
—
Focal length needed
—
Horizontal FOV
—
Max shutter time
—
Plate pixels if the view spans all lanes
—
Pixel density
—
Scene width = horizontal pixels × plate width ÷ pixels on plate. Focal length = sensor width × distance ÷ scene width. Max shutter keeps transverse motion under 14 mm: 0.0142 m ÷ (speed × sin angle), which reproduces the manufacturer shutter table at 30°.
Angle is over 30°. Plates will be too skewed for most LPR software, and the shutter figure is not reliable. Move the camera closer to in line with traffic.
Questions
How many pixels does a license plate need?
At least 75 pixels across a European 520 mm plate to resolve the characters, and 100 to 150 for most LPR software. Use the same pixel count across a 12 in US plate.
What camera angle works for plates?
Keep the total angle between the camera and the direction of travel under 30°, so the plate is seen close to head on.
What shutter speed stops plate blur?
It depends on speed and angle. At 30° the recommended maximum is 3.4 ms at 30 km/h, 2.0 ms at 50 km/h and 1.3 ms at 80 km/h; this calculator uses the same relationship for any speed and angle.
Can one camera cover two lanes?
Yes if the scene width at your pixel target is wider than both lanes. If not, use a higher resolution or one camera per lane.