Enter the nominal diameter of the rebar, the stress in bar at design load, and the design bond stress into the Development Length Calculator. The calculator will evaluate the Development Length. 

Development Length Formula

The following formula is used to calculate the Development Length. 

DL = D*S / (4*BS)
  • Where DL is the Development Length ( )
  • D is the nominal diameter of the rebar 
  • S is the stress in bar at design load 
  • BS is the design bond stress 

To calculate a development length, multiply the nominal diameter of rebar by the stress in the bar at design load, then divide by 4 times the design bond stress.

How to Calculate Development Length?

The following two example problems outline the steps and information needed to calculate the Development Length.

Example Problem #1

  1. First, determine the nominal diameter of the rebar.
    • The nominal diameter of the rebar is calculated to be : 2.5.
  2. Next, determine the stress in bar at design load.
    • The stress in bar at design load is measured to be: 2000.
  3. Next, determine the design bond stress.
    • The design bond stress is found to be: 1500.
  4. Finally, calculate the Development Length using the formula above: 

DL = D*S / (4*BS)

The values provided above are inserted into the equation below and computed.

DL = 2.5*2000 / (4*1500) = .833

Example Problem #2

The variables required for this problem are provided below:

nominal diameter of the rebar = 3

stress in bar at design load = 1000

design bond stress = 5000

Test your knowledge using the equation and check your answer with the calculator.

DL = D*S / (4*BS) = ( )