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Pavement Design

CBR & Subgrade Correlations Calculator

Convert CBR or DCP index values into Resilient Modulus (MR) and Modulus of Subgrade Reaction (k) using standard AASHTO and MEPDG empirical equations.

AASHTO 1993NCHRP 1-37AUSACE

Inputs

Demo

Input Parameters

Input Guidelines

The AASHTO 1993 Resilient Modulus (MR) correlation (MR = 1500 × CBR) is generally valid only for fine-grained soils with a CBR less than 10%.

For higher CBR values, the MEPDG (MR = 2555 × CBR0.64) is often more appropriate.

Results

Correlated Parameters

Enter a valid CBR or DCP value to see correlations.

Theory and formulae

Correlation Formulations

About this calculator

This free cbr correlations calculator runs entirely in your browser: what you enter is never uploaded. Use the calculation steps and the theory section to check the working, and print a calculation sheet with the inputs, results and formulae for your records.

Methods and references: AASHTO 1993, NCHRP 1-37A, USACE.

Topics: cbr, dcp, resilient modulus, subgrade reaction, pavement, k-value, subgrade.

Engineering notice: Results are for preliminary estimation, screening and education. All inputs and outputs must be independently verified by a qualified professional engineer before use in any design or construction decision. Read the full disclaimer