Privacy Fence Sightline Calculator

A boundary fence cannot move, so the question is what it actually hides. This calculator shows the part of your yard that stays out of sight behind the fence and how much extra height would be needed for the rest.

Updated September 13, 2026

Advanced: measurements

Observers1/1

Every place someone could look from. Positions are measured from a reference line, usually the wall of the neighboring building that faces you: “distance” runs toward your private area, “offset” runs left/right.

Neighbor’s raised deck

Name

Type

Include in calculation

Distance from reference line

Left/right offset

Floor level above ground

Eye level above that floor

Viewpoint height used: 2.60 m · 2.32 m · ✕ visible

Private area

What do you want hidden?

Height to hide

Distance from reference line to near edge

Area depth

Area width

Left/right offset of center

Area floor elevation

Screen / barrier

Type

Distance from reference line

Screen height

Size the width automatically to what is needed

Screen width (run)

Left/right offset of center

Rotation

Ground elevation at the screen

Privacy safety margin

Minimum screen height2.22 m

Recommended with margin2.32 m

Still visible

Full results ↓

Screen position3.00 m

Screen height1.80 m

Tip: every handle can be focused with Tab and moved with arrow keys (Shift = larger steps).

Required height by screen position

Hidden
Visible
Fence
Limiting sightline
Blocked beyond the screen

Minimum screen height

2.22 m / 7 ft 4 in

Recommended with margin: 2.32 m / 7 ft 8 in

Still visiblePart of the private area can still be seen.

Current screen height: 1.80 m
Minimum required: 2.22 m
Recommended with margin: 2.32 m
Difference: −0.52 m
Width needed: 3.00 m
Current width: 14.00 m
Coverage: 0%
Protected area: 0.00 m²
Visible area: 30.0 m²
Distance from private area: 3.00 m
Distance from limiting observer: 3.00 m
Limiting observer: Neighbor’s raised deck

Required values are rounded up to the displayed precision. Result accuracy depends on your measurements.

Geometric height required. This is not a statement of what local rules allow. Check local rules before building.

Why this result

At this position, the highest sightline runs from Neighbor’s raised deck to the far edge of the private area. It crosses the screen line 2.22 m above the screen’s base.

Adding your 0.10 m safety margin produces a recommended height of 2.32 m.

To catch the outermost sightlines, the screen must run 3.00 m.

The screen is 0.52 m lower than recommended, and about 100% of the private area remains visible.

Moving the screen 1.00 m closer to the private area would lower the required height to 2.20 m, but it would need to run 4.00 m. A screen closer to the area intercepts the downward sightline lower, and catches a wider spread of sightlines.

Calculations run locally in your browser. Your measurements are not sent anywhere.

Compare screen positions

Moving a screen can change the required height dramatically. Compare up to three positions using your current observers, private area and margin.

Compare screen positions
Option	Screen distance	Height needed	Width needed	Approx. screen area	Coverage with your current screen
Option ANear the observer	Option A: Screen distance 4.50 m from private area	2.51 m	1.50 m	3.76 m²	0%
Option BHalfway	Option B: Screen distance 3.00 m from private area	2.32 m	3.00 m	6.95 m²	0%
Option CNear the private area	Option C: Screen distance 0.90 m from private area	2.06 m	5.10 m	10.5 m²	58%

Across these options the height needed ranges from 2.06 m to 2.51 m.

Find best position

Tell the planner where a screen could go and your limits. It tests hundreds of positions and shows options that satisfy them.

Allowed zone starts at

Allowed zone ends at

Maximum acceptable height (optional)

Maximum acceptable width (optional)

Saved plans

Plan name

No saved plans yet. Plans are stored only in this browser.

Minimum screen height: 2.22 m Still visible

Results

Minimum screen height	2.22 m (7 ft 4 in)
Recommended with margin	2.32 m (7 ft 8 in)
Width needed	3.00 m (9 ft 11 in)
Current screen height	1.80 m
Current width	14.00 m
Coverage	0%
Protected area	0.00 m²
Visible area	30.0 m²
Distance from private area	3.00 m
Limiting observer	Neighbor’s raised deck
Result	✕ Still visible

At this position, the highest sightline runs from Neighbor’s raised deck to the far edge of the private area. It crosses the screen line 2.22 m above the screen’s base.

Adding your 0.10 m safety margin produces a recommended height of 2.32 m.

To catch the outermost sightlines, the screen must run 3.00 m.

The screen is 0.52 m lower than recommended, and about 100% of the private area remains visible.

Diagrams

Side view

Top view

Measurements

Observers: Neighbor’s raised deck	Person / door · Distance from reference line: 0.00 m · Left/right offset: 0.00 m · Floor level above ground: 0.90 m · Eye level above that floor: 1.70 m · Viewpoint height used: 2.60 m
Private area	Patio seating (seated adults) · Distance from reference line to near edge: 6.00 m · Area depth: 5.00 m · Area width: 6.00 m · Left/right offset of center: 0.00 m · Area floor elevation: 0.00 m · Height to hide: 1.20 m
Screen / barrier	Fence · Distance from reference line: 3.00 m · Screen height: 1.80 m · Screen width (run): 14.00 m · Left/right offset of center: 0.00 m · Rotation: 0° · Ground elevation at the screen: 0.00 m
Privacy safety margin	0.10 m

Geometric estimate based on the measurements entered. It does not replace checking on site, professional measurement, engineering or architectural advice, or local rules and permits. Check local rules before building.

Created with Privacy Sightline Planner.

The example above shows a neighbor on a raised deck, a 1.80 m (5 ft 11 in) fence 3 m in front of them, and a seating area beyond. Drag the fence top, change the viewer or switch units; the hidden and visible parts of the seating area update immediately.

The privacy shadow of a fence

Think of the fence as casting a “shadow” of privacy, the way it casts a shadow from a low sun. The viewer’s eye is the light source. Everything within the shadow, up to the height you want hidden, is out of sight.

The green band on the ground marks the depth of yard in which seated people (1.2 m) are hidden.

The depth of that shadow follows from similar triangles:

shadow depth = distance from viewer to fence × (fence height − height to hide) ÷ (eye height − fence height)

For the deck viewer above: 3 × (1.8 − 1.2) ÷ (2.6 − 1.8) = 2.25 m. Beyond that, seated people become visible over the fence.

Two consequences are worth remembering:

If the viewer’s eyes are below the fence top, the shadow is unlimited — they cannot see over it.
If what you want hidden is as tall as the fence, there is no shadow at all: standing people behind a 1.8 m fence are visible from any elevated viewpoint.

How deep is the shadow of a 1.8 m (6 ft) fence?

Viewer 3 m (9 ft 10 in) in front of the fence:

Viewer	Reclining (0.9 m)	Seated (1.2 m)	Standing (1.8 m)
Person standing on level ground — eyes at 1.70 m (5 ft 7 in)	Entire yard (viewer below fence top)	Entire yard (viewer below fence top)	None
Person on a deck 0.9 m (3 ft) high — eyes at 2.60 m (8 ft 6 in)	3.38 m (11 ft 1 in)	2.25 m (7 ft 5 in)	None
Second-floor window — eyes at 4.60 m (15 ft 1 in)	0.96 m (3 ft 2 in)	0.64 m (2 ft 1 in)	None
Third-floor window or balcony — eyes at 7.60 m (24 ft 11 in)	0.47 m (1 ft 6 in)	0.31 m (1 ft 0 in)	None

From a second-floor window, a 1.8 m fence hides seated people only in a narrow band right behind it. That is why a boundary fence alone rarely solves overlooking from upper floors; see blocking a second-story neighbor’s view.

Using the calculator for a fence

In the Screen / barrier section, choose Fence, turn off automatic width and enter the fence’s real length and position.
Enter each viewpoint that overlooks the yard as an observer — decks, windows, balconies.
Define the area you care about most, not the whole lot, and set how high people there need to be hidden.
Read Coverage, Protected area and Visible area. The recommended height shows what the fence would need at its position to hide everything.
If that height is unrealistic, use Compare screen positions to test a separate screen closer to the seating.

Fence heights near property lines are commonly regulated. The calculator reports geometry only; check local rules before building.

Frequently asked questions

Is a 6 ft (1.8 m) fence tall enough for privacy?

Against people standing on level ground, usually yes: their eyes are below the top of the fence, so they cannot see over it at all. Against anyone elevated — a deck, a sloping lot or an upper floor — a 1.8 m fence only hides a strip of your yard next to it. The table on this page shows how deep that strip is.

Does the distance of the neighbor from the fence matter?

Yes. The privacy shadow is proportional to how far the viewer stands from the fence. A neighbor looking from a deck right against the fence sees much more of your yard than one looking from a window 10 m back.

Should I add a trellis or fence topper?

Extra height at the boundary helps most against low viewpoints close to the fence. Against upper-floor windows, a separate screen or overhead cover near your seating is often more effective than a taller boundary. Check local height limits first; toppers commonly count toward the permitted height.

Can the calculator model a fence on a slope?

Yes. In Advanced mode, set the ground elevation at the fence and the elevation of your private area relative to the viewer’s ground. All sightlines are then calculated with those differences.

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