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Recessed Lighting Calculator

Recessed Lighting Calculator

Enter the required inputs into the calculator and find each recessed lighting fixture's placement and spacing.

Surface Length (A)

Surface Length (B)

Columns of Lighting Fixtures

Rows of Lighting Fixtures


Select Units


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The recessed lighting calculator helps to find the perfect place and spacing for lighting fixtures in no time. This tool is very helpful in planning for the lighting of your ceiling.

What Is A Recessed Lighting?

Recessed lighting means to have a light source that is placed inside the ceiling. An openly installed bulb is not considered as the recessed light.

It is also known as “can lighting” or “pot lighting”. This lighting is commonly used in residential and commercial spaces. 

Recessed Lighting Formulas:

The formulas that are used for the placing and recessed lighting spacing are as follows:

\(Outer Row Offset \ (a_o)  =\dfrac{A}{2*r}\)


  • \(a_{o}\) represents the outer row offset. It is the lowermost fixture from the lower edge of the ceiling
  • A is the surface length
  • R shows the total number of rows of lighting fixtures

Use the following equation to calculate the vertical row spacing:

\(Row\ Spacing \ (a_i)  =\dfrac{A}{r}\)

Calculate the distance of the outer fixtures from the sides of the ceiling with the help of the following formula:

\(Outer\ Row\ Offset \ (b_o)  =\dfrac{B}{2*c}\)


  • \(b_o\) represents the outer column offset. It is the lowermost fixture from the lower edge of the ceiling
  • B is the width of the room
  • C is the total number of columns

To determine the column spacing:

Column Spacing \((b_i)  =\dfrac{B}{c}\)

If you want to have centered lighting then use the following formula for vertical offset:

Centered Lighting’s Vertical Offset \((y_o)  =\dfrac{A}{r}\)

For Multiple Centered Lighting:

Centered Lighting’s Vertical Offset \((y_i)  =\dfrac{A}{r}\)

Similarly find the distance of centered lighting from the left or right side of the ceiling:

Centered Lighting’s Horizontal Offset \((x_o)  =\dfrac{B}{2}\)

For multiple-centered lighting:

Centered Lighting’s Spacing \((x_i)  =\dfrac{B}{2}\)

How To Calculate the Recessed Lighting Layout?

Follow the below-mentioned steps to figure out how to lay out recessed lighting:

  • First of all, measure the room size
  • Determine the purpose and the lightning goals. Different rooms may require different types of lighting
  • Create a rough sketch on paper
  • Choose the right lighting layout for your room such as a grid, center layout, etc
  • Decide the number of lights that will be placed in each row and column
  • Now divide the length of the row by the number of lights to find the spacing
  • Once you get the spacing, mark the locations on the ceiling and install the lights accordingly!


Suppose you have a rectangular living room with the following dimensions:

  • Surface Length = 10 feet
  • Surface Width = 20 feet

You have two rows and two columns of lights and also want to include centered-positioned lighting. How to measure for recessed lighting, and how far apart should recessed lights be?


Determine the number of lights:

You mentioned that you want two rows and two columns of lights with center lighting so you will have a total of 5 recessed lights.

Determine the number of lights

Calculate the spacing for the columns:

\(Spacing \space between \space columns = \frac{Surface \space Width}{Number \space of \space Columns} = \frac{20 \space feet}{2} = 10 \space feet\)

Calculate the spacing for the rows:

\(Spacing \space between \space rows = \frac{Surface \space Length}{Number \space of \space Rows} = \frac{10 \space feet}{2} = 5 \space feet\)

Outer row offset:

By putting the values in the formula:

\(b_o = \dfrac{20}{2 \cdot 2} = \dfrac{10}{4} = 2.5 \space feet\)

It is the recessed light distance from wall.

Outer column offset:

\(a_o = \dfrac{B}{2*c} =  \dfrac{20}{4} = 5\ feet\)

For centered recessed lighting:

There is one light in the center so:

Centered Lighting’s Vertical Offset \(y_o  =\dfrac{A}{r} = \dfrac{10}{2} = 5\ feet\)

Centered Lighting’s Horizontal Offset \(x_o  =\dfrac{B}{2} = \dfrac{20}{2} = 10\ feet\)

References: Recessed Lighting Layout.