Hardness Conversion Calculator
Convert approximate steel hardness values among Brinell, Vickers, Rockwell C, and Rockwell B scales using table-based interpolation.
Input
Converted hardness
Conversion details
| Scale | Converted value | Status |
|---|---|---|
| Brinell (HB) | 300 | Source value |
| Vickers (HV) | 303 | Equivalent |
| Rockwell C (HRC) | 29.8 | Equivalent |
| Rockwell B (HRB) | Not available | Outside overlap |
How to use this hardness conversion calculator
What this calculator does. This tool estimates equivalent hardness numbers for non-austenitic steel across four common indentation scales: Brinell hardness (HB), Vickers hardness (HV), Rockwell C (HRC), and Rockwell B (HRB). It uses a discrete engineering conversion table and linear interpolation between neighboring rows. The result is a practical comparison, not a new hardness test and not a universal identity for every alloy, heat treatment, thickness, surface condition, or test load. ASTM explains that hardness conversion tables are separated by material class because the relationships are empirical rather than exact; see the scope of the ASTM E140 hardness conversion tables.
When to use it. Use the calculator when reviewing a drawing that specifies one scale while a certificate reports another, when comparing supplier data sheets, when estimating whether a test result is near a process target, or when preparing a preliminary inspection plan. For final product acceptance, use the scale named by the governing specification whenever possible.
How to calculate. The calculator opens with a complete demonstration: Brinell hardness is selected and the value is 300 HB. The first result and the Excel workbook are ready immediately.
- Choose Known hardness scale to match the original measurement.
- Replace the demonstration number in Hardness value with your measured or specified value.
- Read the primary conversion, the three supporting result cards, and the detail table. A dash or “Not available” means the chosen table does not provide a defensible overlap for that scale at the current hardness.
- Select Download Excel to save the current inputs and typed outputs in a validated .xlsx workbook. Select Reset to clear the demonstration data; export then remains unavailable until a complete valid input is entered again.
Input guide. Known hardness scale is required and accepts one of four fixed options: Brinell hardness (HB), Vickers hardness (HV), Rockwell C (HRC), or Rockwell B (HRB). Choose the scale actually reported by the test, not the scale you want to obtain. For example, select Brinell when the certificate says 300 HB. Changing the source scale changes which column is searched and may change the usable range. Hardness value is also required. Enter one plain positive decimal, such as 300, 303, 29.8, or 95. Scientific notation, unit text, grouping commas, and decimal commas are rejected so an ambiguous entry cannot be silently reinterpreted. Values outside the table range are rejected rather than extrapolated because extrapolation can imply unsupported precision.
Output guide. Vickers hardness, Brinell hardness, Rockwell C, and Rockwell B display the approximate equivalents available at the same table position. HB and HV are shown as whole hardness numbers; HRC and HRB are shown to one decimal place. Conversion position says whether the input matches an exact table row or was interpolated between two rows. The summary pills repeat the source, range state, and method. The detail table identifies the source row, each equivalent, and any unavailable scale. High or low numbers should be interpreted only within the selected scale; the numeric magnitudes of different scales are not directly comparable.
Worked example. With the startup values, the source is 300 HB. The table row used by this calculator gives approximately 303 HV and 29.8 HRC. Rockwell B is not reported at this hardness because the B scale is mainly used in a softer range and the selected table does not provide a reliable overlap here. Therefore the first-open primary result is 303 HV, the Brinell card remains 300 HB, and the Rockwell C card shows 29.8 HRC.
Why hardness conversions are approximate
Hardness is resistance to localized plastic deformation, but each method creates and measures an indentation differently. The Brinell test uses a ball and calculates hardness from load and indentation geometry. The Vickers test uses a diamond pyramid and derives a number from the diagonal lengths of the impression. Rockwell measures permanent indentation depth under specified minor and major loads. The ASTM E10 Brinell method, ASTM E18 Rockwell method, and ASTM E92 Vickers method therefore define different test procedures and validity requirements.
Because the relationship depends on material response, a conversion should be treated as an estimate suitable for communication and screening. Surface finish, specimen thickness, indentation spacing, curvature, decarburization, anisotropy, and work hardening can all influence the original test. A converted number cannot correct a poor test or substitute for the required scale on a purchase specification.
Interpolation method and limits
The calculator locates the two nearest rows in the selected source column. If the input equals a listed row, it returns that row directly. Otherwise it calculates the fractional position between the two source values and applies that same fraction to each target column when both target values exist.
No extrapolation is performed beyond the supported table. A target is also withheld when one of the bounding rows lacks that scale, preventing interpolation across an undocumented gap. This conservative behavior is especially important near the transition between Rockwell B and Rockwell C.