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Rebar Development Length Calculator

Calculate basic reinforcing steel development or anchorage length from bar diameter, steel stress, and design bond stress, with an optional lap splice calculation.

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Reinforced concrete

Rebar Development Length Calculator

Calculate the basic straight-bar development (anchorage) length from bond equilibrium. A lap splice — often called an overlap — is related, but it is not the same thing.

Terminology: Development length \(l_d\) is the embedment needed to develop force in one bar. A lap splice transfers force between two overlapping bars and may require a code-specific multiple of development length.
mm
MPa
Use the design steel stress required by the governing standard.
MPa
Obtain this value from the governing design code for the actual concrete, bar and bond conditions.
× \(l_d\)
Leave blank unless the applicable code provides a multiplier for the splice condition.

Basic development length

— mm
— m  ·  —\(\phi\)
\[ l_d = \frac{\phi\,\sigma_s}{4\,\tau_{bd}} \]
Based on equilibrium between bar force and uniform bond resistance.
Engineering limitation

This is a basic bond-equilibrium calculator, not a complete code check. Actual development and lap-splice requirements can depend on concrete strength, bar type/coating, cover, spacing, confinement, top-bar position, lightweight concrete, hooks, seismic provisions, bar size, bundled bars and minimum-length rules. Verify the final detailing against the governing project standard and drawings.