How many security cameras do you need?

The question behind the question

Most people ask for a number: four cameras, eight cameras, sixteen. A number is a poor starting point, because two cameras can cover a small home well while twelve can still miss the one door that matters. A better question is: what do I need to be able to see, and how clearly?

Start with the purpose of each camera, not the size of the property.

Think in four purposes

Surveillance practice commonly separates what a camera is for into four levels. Each needs a progressively tighter view of the subject, which is why a single wide camera rarely does everything.

• Detect. You can tell that something, perhaps a person, is there. Good for large open areas such as a yard or car park.
• Observe. You can see what that person is doing and roughly how they are dressed or moving.
• Recognise. You can tell whether it is someone you already know.
• Identify. The image is clear enough to describe a person or read a number plate for a report.

Most properties need detect-level cover over wide areas and recognise- or identify-level cover at a handful of choke points, usually doors and gates. That mix is what drives the camera count.

Entry points first

Walk the property and list every way in. Include the obvious ones (front door, roller door, gate) and the quiet ones (side gate, rear sliding door, a window at the back, a loading dock). Then rank them by how likely they are to be used and how hard a poor image would hurt you.

Every serious entry point earns a camera that looks at the doorway itself, at close range, with the person's face in frame as they pass through. Only after those are covered should you add cameras for open areas, such as a yard, a driveway or the shop floor.

A second rule helps: cover the places people have to pass, not the places they might pass. A narrow side path that leads to the back door is a better spot than the middle of a large lawn.

Worked example: a family house

A single-storey house on a suburban block has a front door, a side gate, a rear sliding door and a garage with a driveway.

• One camera on the front entrance, aimed at the door at a height that catches faces.
• One covering the driveway and garage door, with a view along the approach.
• One on the side gate, because it is the least-seen way to the rear.
• One covering the rear door and yard.

That is four cameras, each tied to an entry point. A fifth for a side window or a long rear fence line is reasonable if the block is large. The page on front entrances goes into these locations in more detail.

Worked example: a small shop

A retail shop has a front door, a counter with a till, a stockroom, a rear delivery door and a floor of shelving.

• One at the front door facing inwards, so customers' faces are captured as they enter.
• One covering the till and counter, where disputes and cash handling happen.
• One or two over the shop floor, aimed down aisles rather than at the ceiling.
• One on the stockroom door, and one on the rear delivery door.

That brings the total to five or six. The temptation is to add many wide cameras on the floor. Fewer well-aimed ones usually give more usable footage. Notes for different trading types are at retail stores.

Worked example: a small warehouse

A warehouse has a roller door, a pedestrian door, a fenced yard, an office and a few rows of racking.

• One on each external door, set to recognise-level.
• Two covering the yard and fence line, wide enough to detect movement across the whole area.
• One at the office entrance.
• One or two down the main aisles or at the dock.

Here the count is six to eight, but the real variation comes from the yard. A large yard may need several wide cameras at the corners, each looking along a boundary rather than at it. After-hours movement is usually the main concern, so see warehouses for how this is usually approached.

Checklist before you settle on a number

• List every entry point and rank them.
• Write one sentence per camera: "This camera must let me ___."
• Choose the purpose level (detect, observe, recognise or identify) for each.
• Note blind spots: corners, vehicles blocking the view, trees.

Use the field-of-view tool to test your plan

Rather than guessing how wide a lens will see, you can sketch it. The field-of-view tool lets you try a distance and a lens and see roughly how wide a scene a camera will cover and how many pixels fall across a person. It will tell you, quickly, whether one camera is enough for a driveway or whether two make sense. The reasoning behind lens choice is explained in camera resolution and lens choice.

What changes the number

Several things push the count up or down.

• Property shape. An L-shaped building has corners you cannot see around.
• Obstructions. Parked vehicles, shelving, vegetation and pillars create blind spots.
• Purpose. If the goal is a general overview, fewer cameras will do. If the goal is evidence, you need closer views at entries.
• Recording. The recorder must have enough channels, and storage must handle the extra footage.

Limits of any estimate

A desktop plan is a starting point. Real sites have surprises: a tree that blocks a view, a wall with no path for a cable. A site visit often changes the plan by a camera or two.

More cameras are not always better. Many wide cameras can still leave no clear face at the door.

If you want a second opinion on a plan, you can get a quote and describe the layout, and we will talk through what each camera would be for.

Frequently asked questions