Inch vs Metric Strength Equivalents
"What is the metric equivalent of Grade 8?" The answer is a strength cousin, not a replacement part. Threads, dimensions and nut standards all differ.
Closest strength matches
| Inch | Tensile (min) | Metric | Tensile (min) |
|---|---|---|---|
| Grade 2 | 74 ksi (510 MPa) | 4.8 / 5.8 | 420 / 520 MPa |
| Grade 5 | 120 ksi (827 MPa) | 8.8 | 800 / 830 MPa |
| Grade 8 | 150 ksi (1034 MPa) | 10.9 | 1040 MPa |
| A574 socket | 180 ksi (1241 MPa) | 12.9 | 1220 MPa |
These tables carry the same figures as the printed sheet below.
The printed sheet
See an error on this sheet?
Tell us what is wrong.
Text version of this sheet
Inch and metric strength cousins · not substitutes
What it is
FIELD IDENTIFICATION
"What is the metric equivalent of Grade 8?" The answer is a strength cousin, not a replacement part.
Threads, dimensions and nut standards all differ.
MFG
MFG
MFG
8.8
MFG
10.9
Gr 5
8.8
Gr 8
10.9
Close in strength - not interchangeable
Closest strength matches
Inch
Tensile (min)
Metric
Tensile (min)
Grade 2
74 ksi (510 MPa)
4.8 / 5.8
420 / 520 MPa
Grade 5
120 ksi (827 MPa)
8.8
800 / 830 MPa
Grade 8
150 ksi (1034 MPa)
10.9
1040 MPa
A574 socket
180 ksi (1241 MPa)
12.9
1220 MPa
Key points
Never thread a metric bolt into an inch nut or the reverse, even when it seems to start.
Across-flats sizes differ, so wrenches and sockets do not match either.
Governing standards: SAE J429 (2014); ISO 898-1:2013; ASTM A574-21. Editions shown are the latest confirmed as of September 2026. The drawing and the governing standard
always take precedence over this sheet.
torquing any fastener. Verify the current governing standard, project documents, OEM requirements, size, thread, coating and lot certification. To the fullest extent permitted by law, The Fastener App disclaims liability
arising from reliance on this reference.
Fastener Guide reference FG-A472DF · thefastenerapp.com/fastener-guide/technical-reference/inch-vs-metric-strength-equivalents · © The Fastener App. Reference only — verify the current governing standard, drawing and manufacturer data before specifying or installing.
