Camera Field of View Calculator
Find a camera's horizontal field of view from its sensor width and lens focal length — the two physical specifications that together determine how wide a scene a camera actually captures.
Inputs
E.g. 6.4mm for a common 1/2.7" CCTV sensor.
- Sensor Width (mm)
- Focal Length (mm)
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Saved Scenarios
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Horizontal Field of View (°)
77.3
Spark says
Formula
- Sensor\ Width
- — Physical width of the camera's image sensor
What is the Camera Field of View Calculator?
A lens's field of view depends on both its focal length and the camera sensor's physical size — the same focal length gives a different FOV on different sensor sizes, which is why this calculator needs both.
Use this when choosing a lens focal length to achieve a specific coverage width, comparing two cameras' effective field of view when they use different sensor sizes, or verifying a manufacturer's stated FOV specification against the underlying sensor and lens numbers.
How to use it
- 1 Enter the camera sensor's physical width in millimeters (check the camera's datasheet).
- 2 Enter the lens focal length in millimeters.
Understanding Camera Field of View Calculator
Field of view is one of those camera specifications that seems like it should depend on a single number — the lens's focal length — but actually depends on the interaction between two physical measurements, and understanding why reveals something genuinely useful about how to compare cameras fairly.
A lens's focal length describes how strongly it bends (refracts) light to focus an image onto the sensor behind it — a shorter focal length bends light more sharply, spreading a wider angle of the scene across the sensor, while a longer focal length bends light more gently, concentrating a narrower slice of the scene onto the same sensor area. This is the familiar wide-angle-versus-telephoto tradeoff. But the sensor's physical size matters just as much, because field of view is fundamentally about the angle subtended between the lens and the edges of the sensor — a larger sensor captures a wider angle for the same focal length simply because its physical edges are farther from the lens's optical center, geometrically subtending a wider angle even though the light is being bent by exactly the same amount.
This interaction is exactly why quoting a lens's focal length alone, without also specifying the sensor size it's paired with, doesn't actually tell you the resulting field of view — the same 4mm lens produces a meaningfully different FOV mounted on a large sensor versus a small one. This is a genuinely common point of confusion when comparing cameras, especially across different manufacturers or product lines that may use different sensor sizes even within a similar price range or product category — two cameras both advertising a '4mm lens' can have noticeably different actual coverage if their sensor sizes differ, and a fair comparison requires looking at both numbers together, exactly as this calculator does.
It's also worth being clear about what 'field of view' means directionally. A camera's horizontal FOV, vertical FOV, and diagonal FOV are all different values, because most camera sensors are rectangular (wider than tall) rather than square — the sensor's edges are geometrically closer to the optical center in the vertical direction than the horizontal direction (assuming a standard landscape-oriented sensor), which means vertical FOV is always narrower than horizontal FOV for the same lens and sensor. Manufacturer specifications sometimes quote only one of these three figures without clearly labeling which, which is worth double-checking when a stated FOV number seems inconsistent with a camera's other specifications or with real-world coverage observations.
For CCTV and security camera selection specifically, this relationship has a direct practical consequence: choosing a wider field of view (through a shorter focal length or a larger sensor) always trades off against per-pixel detail on any given subject at a fixed distance, since the same total sensor resolution is being spread across a wider real-world area. A camera optimized for wide-area general monitoring will show less per-subject detail than a camera with a narrower FOV covering the same distance, which is exactly why identification-focused camera placements (entrances, cash registers) typically favor a narrower FOV and closer placement over the wide-area coverage that's appropriate for general perimeter monitoring.
Worked examples
Advantages
- •Correctly accounts for both sensor size and focal length, rather than assuming focal length alone determines FOV.
- •Makes it possible to compare field of view fairly across cameras with different sensor sizes.
- •Useful for choosing the right lens focal length to achieve a specific desired coverage angle.
- •Simple two-input calculation based on well-established optical geometry.
Limitations
- •Calculates the horizontal FOV along the sensor's width only — vertical and diagonal FOV differ and depend on the sensor's aspect ratio.
- •Assumes an ideal rectilinear lens — wide-angle and fisheye lenses with significant optical distortion don't follow this simple geometric formula precisely near the edges of the frame.
Common mistakes
- ⚠️ Assuming focal length alone determines field of view, without accounting for sensor size — the same lens focal length produces a dramatically different FOV on a larger versus smaller sensor.
- ⚠️ Comparing two cameras' 'FOV' figures without checking whether both used the same sensor size assumption, since manufacturers sometimes quote FOV without clearly specifying the sensor it's based on.
- ⚠️ Assuming horizontal, vertical, and diagonal FOV are all the same value, when they genuinely differ based on the sensor's aspect ratio (typically wider than tall).
Tips
- 💡 Always check a camera's actual sensor size (from its datasheet) before comparing FOV across different camera models, since the same lens can produce very different FOV on different sensors.
- 💡 For a specific desired coverage angle, work backward from this formula to choose the right focal length for your camera's specific sensor size, rather than assuming a focal length that worked well on a different camera will produce the same result.
- 💡 Remember that wider FOV (shorter focal length) trades off against per-pixel detail at a given distance — a wide-angle camera covers more area but captures less detail on any specific subject within that area.
- 💡 For wide-angle or fisheye lenses specifically, treat this calculator's result as an approximation near the frame edges, since those lens types introduce distortion that a simple geometric formula doesn't capture precisely.
Real-life uses
- Choosing a lens focal length to achieve a specific desired coverage width
- Comparing field of view fairly across cameras that use different sensor sizes
- Verifying a manufacturer's stated FOV specification against the underlying numbers
- Planning camera placement and angle based on expected coverage width at a given distance
Frequently asked questions
Why does a shorter focal length give a wider FOV?
A shorter focal length bends light more sharply onto the sensor, capturing a wider angle of the scene — this is the basic trade-off between wide-angle and telephoto lenses.
Why does sensor size matter for field of view, not just focal length?
Field of view depends on the angle subtended between the lens and the sensor's physical edges — a larger sensor's edges are farther from the lens's optical center, geometrically capturing a wider angle even with the identical focal length.
Is horizontal FOV the same as vertical FOV?
No — most sensors are rectangular (wider than tall), so vertical FOV is narrower than horizontal FOV for the same lens and sensor, since the sensor's vertical edges sit closer to the optical center.
Does wider field of view mean better image quality?
Not necessarily — wider FOV spreads the same total sensor resolution across a larger real-world area, reducing per-pixel detail on any specific subject at a fixed distance compared to a narrower FOV.
Does this formula work accurately for wide-angle or fisheye lenses?
It's a close approximation for standard rectilinear lenses, but wide-angle and fisheye lenses introduce optical distortion near the frame edges that this simple geometric formula doesn't precisely capture.
calixo.cloud/cctv-networking/camera-fov-calculator/ — free calculator, no signup required.