How to use this calculator
Use Convert FOV when you know an angle and aspect ratio. Choose horizontal, vertical or diagonal, then enter a preset ratio or exact pixel dimensions. Use Screen setup to match a single flat monitor: enter its visible diagonal and the distance from your eyes to its center. Use Camera coverage to estimate the rectangle captured at a known distance from horizontal and vertical angles. Add image resolution to estimate pixel density. All modes update immediately and keep your inputs when you switch.
The math behind it
Aspect = width ÷ height Vertical FOV = 2 × atan(tan(horizontal FOV ÷ 2) ÷ aspect) Horizontal FOV = 2 × atan(tan(vertical FOV ÷ 2) × aspect) Diagonal FOV = 2 × atan(√(tan²(horizontal FOV ÷ 2) + tan²(vertical FOV ÷ 2))) Screen width = diagonal × aspect ÷ √(aspect² + 1) Screen height = diagonal ÷ √(aspect² + 1) Screen FOV = 2 × atan(screen dimension ÷ (2 × eye distance)) Coverage dimension = 2 × camera distance × tan(FOV ÷ 2) Coverage area = coverage width × coverage height Pixel density = image pixels ÷ coverage dimension Pixel footprint = coverage dimension ÷ image pixels Use consistent length units. Angles are displayed in degrees; trigonometry is evaluated in radians.
A worked example
A horizontal FOV of 90° at 16:9 corresponds to a vertical FOV of 58.72° and a diagonal FOV of 97.85°. For camera coverage, a 90° horizontal and 90° vertical view at 0.5 m covers a 1 m × 1 m rectangle. With a 1,000 × 1,000 pixel image, that is 1,000 pixels per meter in each direction, or 1 mm per pixel.
Assumptions & precision
Angle conversion assumes rectilinear perspective, a centered view and square pixels. Screen setup assumes a single flat screen perpendicular to a centered viewer; it does not model curved panels, triple monitors or bezels. Camera coverage assumes a pinhole camera facing a flat, perpendicular plane, with distance measured from the projection center; using the camera housing as the starting point is an approximation. Tilt and lens distortion are excluded. Camera angles and pixel dimensions are independent inputs, allowing cropped or resampled images; density is an average, not a promise of measurement accuracy. Angles must be above 0° and below 180°. Unrepresentable geometry is rejected. Results round for display only: angles to 2 decimals, coverage to 3 and pixel footprint to 6.
Common questions
Why is horizontal FOV larger on a wide screen?
At the same viewing distance, a wider viewport spans a larger angle. FOV conversion uses tangent and arctangent, not a direct multiplication of angles.
Which FOV value should I enter in my game?
Use the direction and convention documented by your game or simulator. Some settings use vertical angles, others horizontal angles, and some use a reference aspect ratio or a multiplier. This calculator reports geometric angles; it does not translate every game's slider or adjust sensitivity.
What is the best FOV for sim racing?
Screen setup gives the geometric match for your flat screen size and eye distance. It is a starting point for matching real and virtual scale, not a universal comfort setting. A larger screen or shorter viewing distance spans a wider angle.
Can I use this for a curved or triple-monitor setup?
The screen setup mode is for one flat monitor. Curvature, side-monitor angles, different screen sizes and bezels require additional geometry. Do not multiply the single-monitor result by three.
Does more pixels per millimeter mean that level of accuracy?
No. Pixel density describes sampling across the estimated coverage. Lens quality, focus, distortion, lighting and calibration also affect what can be resolved or measured. Treat the value as a planning estimate.