ISO 898-1 Metric Property Classes Overview
Metric fastener strength is a property class, not a grade. The first number x 100 is nominal tensile in MPa; the second number x 10 is the yield ratio in percent.
ISO 898-1 property classes
| Class | Tensile Rm (min) | Yield (min) | Proof stress |
|---|---|---|---|
| 4.6 | 400 MPa | 240 MPa | 225 MPa |
| 4.8 | 420 MPa | 340 MPa | 310 MPa |
| 5.8 | 520 MPa | 420 MPa | 380 MPa |
| 8.8 (to M16) | 800 MPa | 640 MPa | 580 MPa |
| 8.8 (over M16) | 830 MPa | 660 MPa | 600 MPa |
| 9.8 (to M16 only) | 900 MPa | 720 MPa | 650 MPa |
| 10.9 | 1040 MPa | 940 MPa | 830 MPa |
| 12.9 | 1220 MPa | 1100 MPa | 970 MPa |
Example: 8.8 = 800 MPa nominal tensile, yield 80% = 640 MPa. Governing standards: ISO 898-1:2013; ISO 898-2:2022. Editions shown are the latest confirmed as of September 2026. The drawing and the governing standard always take
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
ISO 898-1 · metric property classes overview
What it is
FIELD IDENTIFICATION
Metric fastener strength is a property class, not a grade. The first number x 100 is nominal tensile in
MPa; the second number x 10 is the yield ratio in percent.
MFG
MFG
8.8
10.9
12.9
8.8
10.9
12.9 socket
Property class stamped on the head
ISO 898-1 property classes
Class
Tensile Rm (min)
Yield (min)
Proof stress
4.6
400 MPa
240 MPa
225 MPa
4.8
420 MPa
340 MPa
310 MPa
5.8
520 MPa
420 MPa
380 MPa
8.8 (to M16)
800 MPa
640 MPa
580 MPa
8.8 (over M16)
830 MPa
660 MPa
600 MPa
9.8 (to M16 only)
900 MPa
720 MPa
650 MPa
10.9
1040 MPa
940 MPa
830 MPa
12.9
1220 MPa
1100 MPa
970 MPa
Example: 8.8 = 800 MPa nominal tensile, yield 80% = 640 MPa.
Governing standards: ISO 898-1:2013; ISO 898-2:2022. 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-7A423B · thefastenerapp.com/fastener-guide/technical-reference/iso-898-1-metric-property-classes-overview · © The Fastener App. Reference only — verify the current governing standard, drawing and manufacturer data before specifying or installing.
