Cinema Seating Rows & Sightlines Calculator

How the cinema seating rows and sightlines calculator works

Two questions decide a home cinema seating plan: how many rows fit, and how high each row behind the first has to sit so its viewers can see the whole picture over the heads in front. The calculator answers both.

For the count, each row takes one row spacing, the seat plus its legroom, measured from the front edge of the first row: rows = ⌊(D − g) ÷ s⌋, where D is the room depth, g the distance from the screen to the first row and s the row spacing. The back row needs its own full spacing too, which is why a row that would start right at the back wall is not counted.

Sightlines and the C-value

Stadium and theatre designers measure sightlines with a C-value: how far a viewer's line of sight to the point they need to see passes above the eyes of the person in front. A head rises some way above the eyes, so a small C-value means looking between heads and a larger one clears them. The Guide to Safety at Sports Grounds, the Green Guide, uses it for seated spectators, and its C-value table is reproduced in this stadium design tutorial: 60 mm means looking between the heads in front, 90 mm seeing well with the head tilted back, and 120 mm the optimal standard. A CAADRIA conference paper on stadium sightlines gives the formula and quotes UEFA's guidance of 90 to 120 mm as the optimum and 60 mm as the minimum.

Rearranged to give the riser, the rise of each row over the one in front:

N = (R + C)(D + T) ÷ D − R

R is the seated eye height of the row in front above the bottom of the picture, D that row's distance from the screen, T the row spacing and C the chosen C-value. In a home cinema the point of focus is the bottom edge of the image. The calculator works row by row, adding each riser to the eye height before working out the next one, and measures D to each row's front edge. That is slightly short of the eyes, so the risers come out a little on the generous side.

Worked through

With the metric defaults, a 6 m room with the first row 3.0 m from the screen and rows 1.05 m apart fits two rows, with 0.9 m left behind the back one. The seated eye height is 1100 mm and the picture starts 600 mm off the floor, so R is 0.5 m. At the optimal C-value of 120 mm, the second row needs (0.5 + 0.12) × (3.0 + 1.05) ÷ 3.0 − 0.5 = 0.337 m, a riser of about 337 mm, which puts the back-row eyes 1.44 m above the floor. In US units the defaults of a 20 ft room, first row at 10 ft, 3½ ft spacing, 43 in eye height and a picture starting at 24 in give a riser of about 13 in.

Risers grow row by row, because each row sits higher above the bottom of the picture than the last. Put four rows into the same 6 m room by moving the first row to 1.8 m and the back row has to sit about 1.57 m above the front one. No ordinary ceiling allows that, which is why most home cinemas stop at two or three rows.

Three ways to lower the riser

Raise the picture. Lifting the bottom of the screen from 600 to 900 mm in the default room cuts the riser from 337 to 232 mm, because the sightline has less far to drop. Check the screen height against the front row's viewing angle.

Stagger the seats so the back row looks between heads rather than over them. That is the 60 mm case, and in the default room it brings the riser down to 256 mm.

Or move the first row back. A longer distance to the screen flattens every sightline, at the cost of a smaller-looking picture.

Headroom and steps

The result gives the back-row eye height above the floor. Add the head above the eyes and the clearance you want, and compare it with the ceiling, especially where a projector or its beam passes overhead. A platform over a normal step height needs a step, built and lit to the stair rules where you live, with a clear route to the exit.

What this tool does not do

It assumes every seat has the same eye height and every row the same spacing, and it measures to the bottom of the picture straight ahead. Wide rooms, curved rows and seats well off-centre need a proper section drawing. The row spacing should come from the seats you intend to buy: recliners need their reclined depth plus room to walk behind them.

Using this calculator with other BuildMetricLab tools

The TV size and viewing distance tool sets the first-row distance for your screen, and the speaker layout tool positions the sound around the rows. All BuildMetricLab tools run in your browser with no sign-up, and the formula is on the page so the maths can be checked.