Enter the length of the overhand and the effective depth into the calculator to determine the effective span of a slab.

## Effective Span of Slab Formula

The following equation is used to calculate the the effective span of a slab.

ES = LO + 1/2*ED

• Where ES is the effective span (ft)
• LO is the length of the overhang (ft)
• ED is the effective depth (ft)

## What is an Effective Span of a Slab?

Definition:

The effective span of slab means the number of feet that a beam is capable of supporting. When determining how many beams are needed for support, you must determine the effective span of the concrete in which it is cast.

The effective span is equal to the actual or gross span minus the distance equal to 1/2″ for every foot of depth. If a beam is cast in 12″ thick concrete, it will be able to support a distance equal to 8″ less than its actual or gross span. That same beam cast in 24″ concrete will be able to span up to 16″ less than its actual or gross span.

The effective length of a concrete column is determined by subtracting from the actual length half the thickness of the slab, plus one-half inch for each foot of depth. Thus, if a column is 40 feet long and cast in 6” thick slabs, it will be able to support 25.5 feet (40 – [6 + 0.5 x 4] = 25.5) less than its length.