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![Steel Unit Converter — MPa, ksi, kgf/mm², mm, inch, °C, °F, J](/images/uploads/9a816a71-0d26-477e-9305-30259e9cd52e/unit-converter-calculator-tensile-specimen-fracture-face-1920x1080.jpg)

Conversion

# Steel Unit Converter

Pick a quantity, type one value, and read it in every unit that quantity uses on a mill certificate. Every factor below is exact by definition — not a rounded constant — and each one is printed on this page. A real GET form: computes correctly with JavaScript off.

   Quantity What are you converting? Strength / stressLength / thicknessMassTemperatureImpact energy (Charpy)Density Units are only offered inside one quantity — a strength can never become a thickness.

   Value Value to convert

 Unit of that value MPaN/mm²ksipsikgf/mm²GPa

  Convert [Reset](/calculators/unit-converter.md "Reset the calculator to its default values") Recalculates on submit — the same value renders with JavaScript off.

### Result

 Valid range

MPa**355**

ksi**51.488**

psi**51488.4**

kgf/mm²**36.2**

GPa**0.355**

1 MPa = 1 N/mm²

Exact by definition — NIST SP 811, international yard and pound (1959), kgf = 9.80665 N.

**Download as PDF** Result sheet · A4 Run a calculation first — then the sheet is ready to download.

Calculated on SteelEquivalents.com — send us the figures for a quotation.

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## Why steel datasheets disagree about units

A European EN certificate states yield strength in MPa, an ASTM one in ksi, and an older JIS or GOST document in kgf/mm². All three describe the same steel. The conversions between them are not measurements and carry no tolerance: the inch, the pound and the kilogram-force are each defined exactly, so 1 ksi is 6.894757 MPa and nothing else. Impact energy is the same story — the Charpy figure a mill reports in joules becomes foot-pounds by an exact factor, and the test temperature converts on an affine scale rather than a multiplication. This page prints the factor it used for every line, so a value you copy into a specification can be traced back to its definition.

## The exact factors used on this page

| Unit | Exact relation |
|---|---|
| MPa | 1 MPa = 1 MPa |
| N/mm² | 1 N/mm² = 1 MPa |
| ksi | 1 ksi = 6.894757 MPa |
| psi | 1 psi = 0.006894757 MPa |
| kgf/mm² | 1 kgf/mm² = 9.80665 MPa |
| GPa | 1 GPa = 1000 MPa |

## Steel unit conversion — frequently asked

Is 1 MPa the same as 1 N/mm²?

Yes — exactly, not approximately. A newton per square millimetre is a megapascal by definition, so no conversion happens between them and the result panel lists the value once.

Why is the temperature conversion not a simple factor?

Because Celsius and Fahrenheit have different zero points. 0 °C is 32 °F, so the conversion is (v − 32) × 5/9, an affine relation. Multiplying alone would turn a −20 °C Charpy test temperature into nonsense — this calculator carries the offset explicitly for every unit.

What does kgf/mm² mean on an old datasheet?

Kilogram-force per square millimetre, the strength unit used by JIS and GOST documents before SI. One kilogram-force is defined as exactly 9.80665 newtons, so 1 kgf/mm² is exactly 9.80665 MPa — a 50 kgf/mm² tensile grade is a 490 MPa grade.

Why does the converter refuse a temperature below absolute zero?

Because −273.15 °C is the bottom of the scale, and anything below it would print a negative kelvin — a number that looks like an answer but describes nothing. The calculator names the lowest value it will accept in the unit you typed, instead of returning a plausible-looking impossibility.