15-scale lookup
Rockwell Hardness Scale Chart
Scale scope checked against ISO 6508-1:2023; configuration and guidance data adapted from NIST SP 960-5.
Scale-selection warning
Rockwell scales are different test configurations, not interchangeable units. Select the scale using the governing material or product specification, specimen geometry and thickness, expected hardness, and the current test standard.
Search by scale or application, then narrow by category or indenter. Scroll inside the chart to see every column; the Scale column and headers remain visible.
No Rockwell scale matches these filters. Clear one or more filters or search by scale, indenter, or application.
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| Test configuration | Applied forces | Practical guidance range |
Typical applications | Copy | ||||
|---|---|---|---|---|---|---|---|---|
| Indenter | Ball diameter | |||||||
| HRA | Regular | Spheroconical diamond | —Not applicable | 98.07 N (10 kgf) | 588.4 N (60 kgf) | 20–88 HRA | Cemented carbides, thin steel, and shallow case-hardened steel. | |
| HRB | Regular | Ball | 1.588 mm (1/16 in) | 98.07 N (10 kgf) | 980.7 N (100 kgf) | 20–100 HRB | Copper alloys, soft steels, aluminum alloys, and malleable iron. | |
| HRC | Regular | Spheroconical diamond | —Not applicable | 98.07 N (10 kgf) | 1471 N (150 kgf) | 20–70 HRC | Steel, hard cast irons, pearlitic malleable iron, titanium, and deep case-hardened steel. | |
| HRD | Regular | Spheroconical diamond | —Not applicable | 98.07 N (10 kgf) | 980.7 N (100 kgf) | 40–77 HRD | Thin steel, medium case-hardened steel, and pearlitic malleable iron. | |
| HRE | Regular | Ball | 3.175 mm (1/8 in) | 98.07 N (10 kgf) | 980.7 N (100 kgf) | 70–100 HRE | Cast iron, aluminum and magnesium alloys, and bearing metals. | |
| HRF | Regular | Ball | 1.588 mm (1/16 in) | 98.07 N (10 kgf) | 588.4 N (60 kgf) | 60–100 HRF | Annealed copper alloys and thin, soft sheet metals. | |
| HRG | Regular | Ball | 1.588 mm (1/16 in) | 98.07 N (10 kgf) | 1471 N (150 kgf) | 30–94 HRG | Malleable irons, copper-nickel-zinc alloys, and copper-nickel alloys. | |
| HRH | Regular | Ball | 3.175 mm (1/8 in) | 98.07 N (10 kgf) | 588.4 N (60 kgf) | 80–100 HRH | Aluminum, zinc, and lead. | |
| HRK | Regular | Ball | 3.175 mm (1/8 in) | 98.07 N (10 kgf) | 1471 N (150 kgf) | 40–100 HRK | Bearing metals and other very soft or thin materials, subject to anvil-effect limits. | |
| HR15N | Superficial | Spheroconical diamond | —Not applicable | 29.42 N (3 kgf) | 147.1 N (15 kgf) | 70–94 HR15N | Applications similar to HRA, HRC, and HRD where thinner material or shallower case depth requires lighter forces. | |
| HR30N | Superficial | Spheroconical diamond | —Not applicable | 29.42 N (3 kgf) | 294.2 N (30 kgf) | 42–86 HR30N | Applications similar to HRA, HRC, and HRD where thinner material or shallower case depth requires lighter forces. | |
| HR45N | Superficial | Spheroconical diamond | —Not applicable | 29.42 N (3 kgf) | 441.3 N (45 kgf) | 20–77 HR45N | Applications similar to HRA, HRC, and HRD where thinner material or shallower case depth requires lighter forces. | |
| HR15T | Superficial | Ball | 1.588 mm (1/16 in) | 29.42 N (3 kgf) | 147.1 N (15 kgf) | 67–93 HR15T | Applications similar to HRB, HRF, and HRG for thinner-gauge material. | |
| HR30T | Superficial | Ball | 1.588 mm (1/16 in) | 29.42 N (3 kgf) | 294.2 N (30 kgf) | 29–82 HR30T | Applications similar to HRB, HRF, and HRG for thinner-gauge material. | |
| HR45T | Superficial | Ball | 1.588 mm (1/16 in) | 29.42 N (3 kgf) | 441.3 N (45 kgf) | 1–72 HR45T | Applications similar to HRB, HRF, and HRG for thinner-gauge material. | |
Guidance ranges are historical ISO ranges reported in NIST SP 960-5 and are not acceptance limits. HRA measurements above 88 and HRB measurements below 20 are sometimes encountered; use the current governing test method and product specification.
Download options
Download the currently visible rows from this original NIST-derived scale-reference dataset. The file excludes ASTM E140 conversion values and equations.
How to Read a Rockwell Hardness Value
A Rockwell result combines a numerical hardness value with the scale designation. In 60 HRC, 60 is the reported hardness number and HRC identifies the C-scale test configuration. “HRC” is not a unit that can be stripped away; it identifies the diamond indenter and force sequence used to obtain the number.
- 60
- Rockwell hardness number produced by the specified test.
- HR
- Rockwell hardness reporting prefix.
- C
- The named scale, which fixes the indenter and test forces.
Correct interpretation
Compare higher and lower numbers only within the same named scale and valid test context. A bare value such as “60 Rockwell” is incomplete, and 60 HRC is not numerically equivalent to 60 HRB.
HRA vs HRB vs HRC
HRA
Uses a spheroconical diamond indenter with a 588.4 N (60 kgf) total force. NIST lists cemented carbides, thin steel, and shallow case-hardened steel as typical applications.
HRB
Uses a 1.588 mm (1/16 in) ball with a 980.7 N (100 kgf) total force. It is commonly associated with copper alloys, softer steels, aluminum alloys, and malleable iron.
HRC
Uses a spheroconical diamond with a 1471 N (150 kgf) total force. It is widely used for hardened steels, hard cast irons, titanium, and deeper case-hardened material.
How the Rockwell test works
- The indenter contacts the prepared specimen and the preliminary force is applied.
- After the preliminary-force dwell, the machine establishes the first depth reference.
- Additional force raises the applied force to the scale’s total-force level.
- The additional force is removed while the preliminary force remains applied.
- The final depth is measured; the permanent depth increase determines the Rockwell number.
Unlike Brinell and Vickers testing, Rockwell testing does not require optical measurement of an indentation area. It uses the difference between two depth readings in the force cycle.
Within the same scale, a smaller permanent depth increase corresponds to a larger Rockwell number.
h is the net depth increase in millimeters. The constants depend on regular versus superficial testing and diamond versus ball indenters, so this relationship is not a cross-scale converter.
Regular vs Superficial Rockwell Scales
Regular scales use a 98.07 N (10 kgf) preliminary force and total forces of 588.4, 980.7, or 1471 N. Superficial scales use a 29.42 N (3 kgf) preliminary force and total forces of 147.1, 294.2, or 441.3 N. The lighter superficial force family may be useful when the material, case, or available test area cannot support the deeper influence of a regular-scale indentation.
- Regular scales
- HRA through HRK in this ISO-scoped chart; heavier force levels and generally larger affected volumes.
- N scales
- Superficial scales using a spheroconical diamond for harder or case-hardened material under lighter forces.
- T scales
- Superficial scales using a 1.588 mm ball for softer or nonferrous material under lighter forces.
Scale-selection checklist
- Start with the governing specification. If it names a Rockwell scale, use that scale when a valid test can be made.
- Check specimen and case thickness. The plastic deformation zone extends below the measured indentation; stacking thin sheets does not create a valid thick specimen.
- Review expected hardness and indenter risk. A ball may flatten on material that is too hard, while a diamond scale may lose useful sensitivity in an unsuitable range.
- Check edges, curvature, and support. Part width, indentation spacing, curved surfaces, anvil support, and local geometry can bias a reading.
- Consider material homogeneity and surface condition. Grain structure, case depth, coatings, decarburization, roughness, and adjacent hardness zones affect what the indentation represents.
This chart narrows the configuration review; it does not approve a scale for a particular specimen. Current ASTM E18 or ISO 6508-1 requirements and any product-specific standard control the final method.
Hardness Conversion Limits
Rockwell, Vickers, Brinell, Knoop, and other hardness methods do not measure exactly the same response. ASTM E140 states that conversions are valid only for the specific indicated materials and can change with alloy, microstructure, heat treatment, and processing condition. Even a relationship developed for one material contains conversion error.
No universal conversion
Do not interpolate this scale chart to convert HRC to HRB, HV, HBW, tensile strength, or another property. Use a current, material-specific conversion relationship only when the governing specification permits it; direct testing on the specified scale is preferable.
The downloadable dataset therefore includes only scale configurations and NIST-reported guidance ranges. It intentionally excludes ASTM E140 tables, equations, and conversion values.
Worked Rockwell Scale Lookups
Hardened steel specified as HRC
Assumption: The product specification explicitly calls for HRC, and expected values fall within the applicable range.
Lookup: The HRC row shows a spheroconical diamond, 98.07 N (10 kgf) preliminary force, and 1471 N (150 kgf) total force. The historical NIST-reported guidance range is 20–70 HRC.
Interpretation: Those fields identify the configuration to verify. They do not confirm minimum specimen thickness, edge distance, curvature correction, machine verification, or acceptance limits; those checks still come from the current method and product specification.
Thin case-hardened surface
Assumption: The objective is to measure a shallow hardened case, and a regular-scale deformation zone may extend beyond the feature.
Lookup: Filtering to Superficial + Diamond isolates HR15N, HR30N, and HR45N. These use the 29.42 N (3 kgf) preliminary force and total forces of 147.1, 294.2, and 441.3 N.
Interpretation: The N-family is the correct family to examine, but the chart cannot choose among the three loads without expected hardness, case depth, total specimen thickness, geometry, and the governing test requirement.
Sources, Scope, and Dataset Rights
Scale scope checked against ISO 6508-1:2023; configuration and guidance data adapted from NIST SP 960-5 (2001).
The published table is an original 15-row reference assembled from the current ISO public scale scope and the openly reusable NIST guide. The NIST guidance ranges are historical context, not current acceptance limits.
- NIST SP 960-5 — Rockwell Hardness Measurement of Metallic MaterialsJanuary 2001. Test principle and reporting: sections 2.2–2.4; configurations and applications: Table 1; scale selection and historical ranges: section 3.1 and Table 2.
- ISO 6508-1:2023 — Metallic materials — Rockwell hardness test — Part 1Edition 5, December 2023. The public abstract establishes the 15-scale scope used here. Proprietary ISO tables and procedures are not reproduced.
- ASTM E18-25 — Rockwell Hardness of Metallic MaterialsCurrent U.S. method scope and public significance-and-use context. Proprietary test tables, annexes, tolerances, and procedures are not reproduced.
- ASTM E140-12B(2019)e1 — Hardness Conversion Tables for MetalsPublic scope and limitations support the conversion warning. No proprietary conversion table, equation, or dataset is included.
- NIST Open LicenseNIST-authored Technical Series content may be reused with attribution, subject to separately credited third-party material.
Dataset and Source-Check Details
- Dataset
- Rockwell Regular and Superficial Scale Reference — 15 ISO-listed scales
- Publisher
- Turn2Engineering
- Source-controlled fields
- Scale, family, indenter, ball diameter, applied forces, applications, and historical guidance range
- Units
- Force in N with kgf in parentheses; ball diameter in mm with inch fraction
- Known exclusions
- Hardness conversions, tensile-strength estimates, specimen acceptance, and proprietary standard procedures
- Download decision
- Filtered CSV permitted for this NIST-derived scale-reference dataset only
Rockwell Hardness Chart FAQs
HRB uses a 1.588 mm ball and 980.7 N total force, while HRC uses a spheroconical diamond and 1471 N total force. They target different application and hardness ranges, so their numbers are not directly comparable.
A higher number generally indicates greater hardness only within the same Rockwell scale and a valid, comparable testing context. Do not rank bare numbers from different scales.
HRC is common for hardened steels, but the correct scale must be confirmed against the material condition, expected hardness, specimen geometry and thickness, case depth, and governing specification.
Only approximate, material-specific conversions should be used. Alloy, microstructure, heat treatment, and processing affect the relationship, and direct testing on the specified scale is preferred.
No. A Rockwell result is a dimensionless empirical number, but it must always be reported with its scale designation, such as 60 HRC.
Use the Chart as a Configuration Reference
Use the table to identify and compare the named Rockwell configurations, then verify the selected scale, specimen requirements, machine verification, procedure, and acceptance criteria in the current governing standard. Preserve the scale suffix whenever you record, copy, or communicate a result.