How this calculator works
The k in ksi is the SI prefix for one thousand, applied to pounds per square inch. That makes the conversion a pure shift of the decimal point: one ksi is 1,000 psi. The unit is common in North American structural engineering, where steel yield strengths such as 36 ksi or 50 ksi are quoted. psi remains the unit for lower stresses, fluid pressures and material datasheets that predate ksi.
Formula
psi = ksi x 1,000. ksi = psi / 1,000. The factor is exact because ksi is defined as 1,000 psi, not measured.
Worked example
1 ksi = 1,000 psi. 36 ksi = 36,000 psi. 50 ksi = 50,000 psi. 0.5 ksi = 500 psi. 100 ksi = 100,000 psi, which is 689.476 MPa.
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Frequently asked questions
What is the difference between ksi and kip per square inch?
Nothing numerically. A kip is 1,000 pounds-force, so a kip per square inch is 1,000 pounds-force per square inch, exactly one ksi. The two spellings describe the same magnitude.
Why is ksi used for steel but psi for tyres?
Steel stresses are in the tens of thousands of psi, so ksi keeps the numbers short. Tyre and hydraulic pressures are in the tens of psi, where ksi would require tiny decimals.
Is 36 ksi a material property?
36 ksi is a common specified minimum yield strength for structural steel. It is a design value from a standard or specification, not a universal property of all steel. Check the project specification for the grade in use.
How do I convert ksi to MPa?
Multiply by 6.894757293168. For example, 50 ksi is 344.738 MPa. The ksi to MPa page on this site performs that conversion and can return the other way.