Kilopound Per Square Inch (ksi)

US & ImperialCurrent unit

1,000 psi (about 6.895 MPa). Used for the strength of materials such as steel in US engineering.

1 kilopound per square inch = 6,894,757.293 pascals (approximately).

About the kilopound per square inch

Thousands of pounds per square inch get unwieldy to write, so American engineers shortened them to ksi, the kilopound per square inch. Wikipedia notes it is used mostly in materials science, where tensile strength runs to large numbers of psi. One ksi is 1,000 psi, or about 6.895 MPa; NIST gives 6.894757 MPa.

Steel specifications, reinforced concrete and structural design are the typical uses. A concrete compressive strength of 4 ksi corresponds to about 27.6 MPa, and a bolt rated at 60 ksi would be roughly 414 MPa. The related unit Mpsi, a million psi, is used for elastic moduli of metals, so steel at 200 GPa is about 29 Mpsi. Metric countries write all of this in megapascals, which is why engineers working across borders keep the factor 6.895 close at hand.

Sources: Wikipedia: Pounds per square inch; NIST SP 811, Appendix B.8; Wikipedia: Pascal (unit)

Kilopound Per Square Inch conversion chart

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