Compressive Strength Calculator

Calculate masonry prism compressive strength (f'm) based on unit strength, mortar type, and grouting. Used for structural design and code compliance.

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How It Works

The specified compressive strength of masonry (f'm) is determined by unit strength and mortar type per TMS 402/602. Standard CMU blocks are 1,900 psi units. Type S mortar is the standard for structural work. f'm is typically 1,500 psi for standard CMU construction. Grouted prisms have about 85% of hollow prism strength because grout is weaker than the CMU units. Allowable compressive stress (ASD) is 0.25 * f'm. All structural masonry design should be done by a licensed engineer.