Enter the un-reduced design live load per square foot, the live load element factor, and the tributary area into the calculator to determine the reduced live load.

Live Load Formula

The following formula is used to calculate the reduced design live load per ft^2 of the area supported by a member. 

L = Lo * (0.25 + 15 / SQRT (KLL * At ) )
  • Where L is the reduced design live load per ft^2
  • L0 is the unreduced design live load per ft^2
  • KLL is the live load element factor
  • At is the tributary area (ft^2)

To calculate the live load, multiply the unreduced design live load by the result of .25 plus 15 over the square root of the product of the live load element factor and the tributary area.

This formula can further be adjusted for using m^2 for the area. 

 L = Lo * (0.25 + 4.57 / SQRT (KLL * At ) )

Live Load Definition

A live load is defined as the load or force per unit area that a structure is subjected to in addition to its own weight.

Example Problem

How to calculate live load?

First, determine the unreduced live load the structural member is designed for. For this example, the unreduced design live load is 40lb/ft^2.

Next, determine the live load element factor. For this example, the element is an interior column that has a KLL of 4.

Next, determine the tributary area. For this problem, the area is found to be 400 square feet (ft^).

Finally, using the formula above, calculate the reduced live load:

L = Lo * (0.25 + 15 / SQRT (KLL * At ) )

= 40 * (.025 + (15/SQRT(4*400)))

= 16 lb/ft^2