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Rebar Development Length from Bond Stress

Calculate a basic straight-bar development length from bar diameter, steel stress and bond stress.

Updated September 2026

How it works

Calculate a basic straight-bar development length from bar diameter, steel stress and bond stress.

Formula:
lb,basic = φ·σs/(4·τbd); ladj = lb,basic·adjustment factor.

Before you use the result: Minimum lengths, cover, confinement, bar position, hooks and lap rules are code-dependent.

Practical use

Use verified material data and project geometry. Treat results as planning estimates and compare them with the energy/thermal requirements that apply to the project.

Keep units consistent with the source information.
Use project-specific densities, pack sizes and coverage rates where provided.
Round purchasing quantities to supplier packaging and delivery rules.

How to use this calculator: Rebar Development Length from Bond Stress

Calculate a basic straight-bar development length from bar diameter, steel stress and bond stress.

Quick workflow

Enter the project values from the latest drawing, specification or verified site measurement.
Check units, material properties, allowances and any code- or supplier-specific parameters before calculating.
Review the result together with the formula, assumptions and the related checks shown on this page.

Worked example

Example inputs: Bar diameter φ [mm]: 16; Design steel stress σs [MPa]: 435; Design bond stress τbd [MPa]: 2.3; Anchorage adjustment factor: 1.

Using the sample values built into the calculator, the calculation gives approximately: Basic development length: 756.5 mm; Adjusted development length: 756.5 mm.

What the result means

Calculation method: lb,basic = φ·σs/(4·τbd); ladj = lb,basic·adjustment factor.

Before using the result: Minimum lengths, cover, confinement, bar position, hooks and lap rules are code-dependent.

Common questions

What does this calculator do?

Calculate a basic straight-bar development length from bar diameter, steel stress and bond stress.

Which inputs should I verify?

Key inputs to verify include: Bar diameter φ [mm], Design steel stress σs [MPa], Design bond stress τbd [MPa], Anchorage adjustment factor.

Can I use this result for final design or ordering?

Use the result as a transparent planning or checking aid. Final design, code compliance, supplier selection and project-specific decisions still need to be verified where applicable. Minimum lengths, cover, confinement, bar position, hooks and lap rules are code-dependent.

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