What is Kips Per Square Inch (KSI)?

Kips per square inch (KSI) is a stress unit used in structural engineering and material science to measure the force applied over a specific area.

Definition

KSI stands for kips per square inch, where one kip equals 1,000 pounds of force. It is a derivative of PSI (pounds per square inch) scaled up to make it easier to work with large structural loads. In structural engineering, stresses in steel, concrete, and other materials are usually high enough that we end up with numbers that are unwieldy to express in PSI. KSI keeps those figures intact, without changing their meaning.

Purpose

KSI is a standard unit for engineers and material scientists to compare the strength and stress limits of materials used in structural applications. The yield strength, tensile strength, and allowable stress values for concrete and steel are often published in KSI. This makes it easy to determine whether a material can bear the loads a design requires without switching between units mid-calculation.

Examples of Use

Structural Steel: Yield strength for A36 steel is 36 KSI, or 36,000 pounds of force per square inch, before it will permanently deform.
Concrete Design: High-strength concrete mixes are specified in KSI. The values range from 4 KSI to over 10 KSI, depending on the application.
Material Science Testing: Metals, composites, and polymers are tensile and compression tested, and results are reported in KSI for direct comparison to design standards.

Related Terms

Accuracy

Accuracy is the degree to which a measurement, calculation, or result matches the actual or intended value.

SY (Square Yard)

SY(Square Yard) is a unit of measure used for surfaces like flooring, paving, roofing, landscaping, and site work.

Notes

One KSI equals 1,000 PSI or approximately 6.895 megapascals (MPa).
KSI is primarily used in the United States; metric equivalents in MPa are standard elsewhere.
Always confirm which unit system a specification uses before applying published strength values in calculations.

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