Convert tensile strength, yield strength, and proof load values between PSI (pounds per square inch) and MPa (megapascals) instantly. Designed for the fastener industry, this converter includes reference data for common US and metric bolt grades, making it easy to compare specifications across standards.
PSI ⇄ MPa Converter
Conversion Formulas
The conversion between PSI and MPa is based on the exact relationship between the imperial and SI pressure units. Since 1 psi = 6,894.757 pascals and 1 MPa = 1,000,000 pascals, the conversion factors are fixed and precise.
Note: 1 MPa = 1 N/mm² exactly. The ksi (kips per square inch) unit equals 1,000 psi. To convert ksi to MPa, multiply by 6.894757.
Common Fastener Grade Strength Reference
The table below shows tensile strength, yield strength, and proof load for common US (SAE) and metric bolt grades in both PSI and MPa. This makes it easy to compare equivalent grades across standards.
| Grade / Class | Система | Tensile Strength (PSI) | Tensile Strength (MPa) | Yield Strength (PSI) | Yield Strength (MPa) | Proof Load (PSI) | Proof Load (MPa) |
|---|
PSI to MPa Quick Reference Table
Common tensile strength values used in the fastener industry, converted from PSI to MPa.
| PSI | MPa | ksi | Общий Применение |
|---|
Understanding Tensile Strength Units
What is PSI?
PSI (pounds per square inch) is the imperial unit of pressure and stress. It represents the force in pounds applied over one square inch of area. PSI is the standard unit used in US (SAE) fastener specifications for tensile strength, yield strength, and proof load.
What is MPa?
MPa (megapascal) is the SI unit of pressure and stress, equal to one million pascals (1 MPa = 1,000,000 Pa = 1 N/mm²). It is the standard unit used in ISO and metric fastener specifications. Because 1 MPa = 1 N/mm², it directly relates force to cross-sectional area.
What is ksi?
Ksi (kips per square inch) equals 1,000 PSI. It is commonly used in US structural engineering and fastener specifications to express large stress values more conveniently. For example, Grade 8 tensile strength of 150,000 psi is written as 150 ksi.
PSI vs MPa in Fastener Standards
US bolts follow SAE J429 and ASTM standards using PSI. Metric bolts follow ISO 898-1 using MPa. While Grade 5 (120,000 psi ≈ 827 MPa) is close to Class 8.8 (800 MPa), they are not exact equivalents. Always verify with the applicable standard for critical applications.
Conversion Tips for Fastener Engineers
Best Practices
- Use the full conversion factor (0.006894757) for specifications and technical documents
- For quick mental estimates, use 1 MPa ≈ 145 psi or 1,000 psi ≈ 6.9 MPa
- Remember that 1 MPa = 1 N/mm² exactly — useful for stress calculations
- Fastener grade equivalents are approximate; Grade 5 ≠ Class 8.8 exactly
- When converting for procurement, always round up to the next standard grade for safety
- ksi values can be converted to MPa by multiplying by 6.894757
- Proof load, yield strength, and tensile strength all use the same conversion factor
Часто задаваемые вопросы
To convert PSI to MPa, multiply the PSI value by 0.006894757. For example, a Grade 8 bolt with 150,000 psi tensile strength equals 150,000 × 0.006894757 = 1,034.21 MPa. The reverse conversion: multiply MPa by 145.037738 to get PSI.
A Grade 8 bolt has a minimum tensile strength of 150,000 psi, which converts to approximately 1,034 MPa. Its yield strength is 130,000 psi (896 MPa) and proof load is 120,000 psi (827 MPa). These values are per SAE J429 for sizes 1/4" thru 1-1/2".
Да, 1 МПа в точности равен 1 Н/мм2. Эта эквивалентность широко используется в технике крепежное изделие, потому что растягивающее напряжение является силой, разделенной по площади. Когда [2] [0] перечисляет силу в N/mm2, числовое значение идентично MPa.
A Metric Class 10.9 bolt has a minimum tensile strength of 1,040 MPa, which converts to approximately 150,839 psi (1,040 × 145.037738). This is roughly equivalent to a US Grade 8 bolt (150,000 psi). The yield strength is 940 MPa (136,335 psi) and proof load is 830 MPa (120,381 psi).
US (SAE) fastener standards use PSI for tensile strength, yield strength, and proof load, while ISO and metric standards use MPa (or equivalently N/mm²). Engineers working with international supply chains need to convert between both systems to compare specifications, select equivalent grades, and verify compatibility.
The conversion factor 1 psi = 0.006894757 MPa is mathematically exact. However, fastener grade specifications define minimum values, so converted values should be treated as approximate equivalents. For example, Grade 5 (120,000 psi) converts to 827.4 MPa, while Metric Class 8.8 is specified as 800 MPa — they are close but not exact equivalents.
Ksi stands for "kips per square inch" or "thousand pounds per square inch." 1 ksi = 1,000 psi. It is commonly used in US structural engineering and fastener specifications. For example, Grade 8 tensile strength of 150,000 psi can be written as 150 ksi. To convert ksi to MPa, multiply by 6.894757.
Yes. Proof load, yield strength, and tensile strength all use the same pressure/stress units (PSI or MPa). The conversion factor is identical for all three. Simply enter the value in PSI to get MPa, or vice versa. Our bolt grade reference table includes all three properties for common grades.
