Vickers Hardness Number Calculator

Calculate Vickers hardness from test force and indentation diagonals, with unit conversion, diagonal mismatch checks and a calculation summary.

Force input mode

Pick the unit you will enter for the test force. The calculator converts it consistently before computing hardness.

Test force (selected unit)

Applied test force. Enter the force in the unit chosen above.

Diagonal input mode

Use two diagonals when you measured both image directions. Use mean diagonal only if you already averaged them elsewhere.

Diagonal 1 (mm)

First measured indentation diagonal length in millimeters.

Diagonal 2 (mm)

Second measured indentation diagonal length in millimeters.

Advanced options

Reporting

Summary load unit

Chooses the test-force unit shown separately in the calculation summary. It does not change HV or generate a standards-compliant test designation.

Display

Number display format

Choose how numeric outputs are shown. Auto uses normal decimals for moderate values and scientific notation only for very large or very small values.

Decimal places (digits)

Used when display format is fixed decimals or scientific notation. For auto, it sets the target precision for normal-sized values.

Quality check

Diagonal mismatch warning threshold (percent)

If the two diagonals differ by more than this percent relative to their mean, show a warning that the indentation may be irregular or measured poorly.

Vickers hardness number (HV)

Higher HV means a harder material surface under this test method.

Mean diagonal (mm)

This lets you verify the exact indentation size used for HV.

SI equivalent hardness (MPa)

Useful when comparing hardness to other engineering quantities reported in MPa.

SI equivalent hardness (GPa)

Helpful for very high hardness values where MPa becomes a large number.

Calculation summary

Use this as a starting point for lab notes, while still following your lab or standard reporting rules.

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How to use our Vickers Hardness Number Calculator

Choose Force input mode so your Test force (selected unit) is entered in kgf or N correctly.
Enter the applied load in Test force (selected unit). Use a positive value only.
Choose Diagonal input mode. Pick Two diagonals if you measured both directions, or Mean diagonal only if you already averaged them.
If using two diagonals, enter Diagonal 1 (mm) and Diagonal 2 (mm). If using mean mode, enter Mean diagonal (mm).
Open Advanced options to change "Summary load unit", "Number display format", "Decimal places (digits)" or "Diagonal mismatch warning threshold (percent)".
Click Calculate to see "Vickers hardness number (HV)", the mean diagonal, SI-equivalent hardness and "Calculation summary".
Sanity-check the result: a smaller diagonal at the same force should give a higher Vickers hardness number (HV), and the Mean diagonal shown should match the value you expected.
If you used two diagonals, review Diagonal mismatch and any Measurement warning. A large mismatch means you should re-check the indent image, focus, polish, or units before reporting.

Definitions

Force input mode: The unit used for the applied test force, either kgf or N.

Test force (selected unit): The load applied by the Vickers indenter during the test.

Diagonal input mode: Chooses whether you enter both measured diagonals or one already-averaged diagonal.

Mean diagonal: The average indentation diagonal length used in the hardness calculation. In two-diagonal mode, it is the arithmetic mean of Diagonal 1 and Diagonal 2 [4][3].

Vickers hardness number (HV): The classic Vickers hardness result. Higher HV means a harder surface under the same test method.

Diagonal mismatch: The percent difference between the two measured diagonals relative to their mean. Larger values can point to an uneven indent or measurement issue.

SI equivalent hardness: The same hardness result expressed as pressure, shown in MPa or GPa.

Calculation summary: Hardness and test force shown as separate quantities. It is not a complete test-report designation; conventional HV notation uses a kgf-based load designation and may also require dwell time.

Common mistakes and quick fixes

Mistake: Entering newtons while Force input mode is still set to kgf, or the reverse.
Fix: Match Force input mode to the unit used in Test force (selected unit) before you calculate.

Mistake: Typing diagonal values in um but leaving Diagonal 1 (mm) , Diagonal 2 (mm) , or Mean diagonal (mm) in millimeters.
Fix: Convert your microscope reading to mm first. For example, 500 um must be entered as 0.500 mm.

Mistake: Filling Mean diagonal (mm) while Diagonal input mode is set to two diagonals.
Fix: In two-diagonal mode, enter Diagonal 1 (mm) and Diagonal 2 (mm) . In mean mode, enter only Mean diagonal (mm) .

Mistake: Ignoring a large diagonal mismatch because a number was calculated. Fix: Read "Measurement warning" and recheck the indentation or measurement before using the result.

Mistake: Copying a calculation summary as a complete test designation. Fix: Use your applicable test standard and laboratory reporting requirements, including test force and dwell time; the summary alone is not a test report.

Mistake: Assuming SI equivalent hardness in MPa or GPa is a different test result from Vickers hardness number (HV) .
Fix: Treat the MPa and GPa values as conversions of the same hardness result, useful when you need SI-style pressure units.

Limitations & Key Assumptions / Boundary Conditions

This calculator assumes a standard Vickers test using the usual 136 degree pyramid geometry and the classic HV equations.
Results are only as good as the measured diagonal lengths. Poor focus, rough polish, edge effects, or an irregular indent can change the hardness value.
In Mean diagonal only mode, the calculator cannot compute Diagonal mismatch because it does not know the two original measurements.
The MPa and GPa outputs are SI-equivalent conversions of HV, not separate test methods.
Very small diagonal values can produce extremely large HV results. When that happens, verify the microscope scale, decimal place, and force unit carefully.
The calculation summary separates hardness from force. It does not verify test conditions or supply the complete notation and details required by a laboratory, customer or standard.
If Diagonal mismatch warning threshold (percent) is set too low, you may see frequent warnings; if set too high, useful quality-control flags may be missed.

Methodology

Calculation steps

The calculator first determines which force unit you entered. If you enter force in newtons, it converts that value to kilogram-force using standard gravity before calculating HV.

d = (d1 + d2) / 2

F_kgf = F_N / 9.80665

HV = 1.8544 x F_kgf / d^2

Hardness_MPa = HV x 9.80665

Hardness_GPa = Hardness_MPa / 1000

Mismatch_pct = abs(d1 - d2) / d x 100

What each part means

d is the mean diagonal in mm. In two-diagonal mode, it is the average of the two measured indentation diagonals, which is the standard basis for the calculation [1][3]. F_kgf is the test force in kilogram-force. The constant 1.8544 is the standard geometry constant for the Vickers indenter.

Worked mini-example

Suppose Force input mode is kgf, Test force (selected unit) is 10, and both diagonals are 0.500 mm.

d = (0.500 + 0.500) / 2 = 0.500 mm

HV = 1.8544 x 10 / 0.500^2 = 74.176

Hardness_MPa = 74.176 x 9.80665 = 727.273 MPa

Hardness_GPa = 727.273 / 1000 = 0.727273 GPa

The summary is about 74.18 HV with test force 10 kgf, or the equivalent 98.07 N. Changing "Summary load unit" changes only the separate force label; it does not put a Newton value into the conventional HV load designation.

Warnings and interpretation

If you enter two diagonals, the calculator also computes diagonal mismatch. A larger mismatch does not automatically make the HV wrong, but it is a useful quality-control flag because the two diagonals are often slightly distorted in practice [2]. Higher HV means a harder material surface for that test condition.

Assumptions used

This tool assumes positive force and positive diagonal values, standard gravity of 9.80665 N per kgf, and consistent millimeter input for diagonal lengths. It does not adjust for dwell time, surface preparation quality, indenter condition, or lab-specific reporting rules, all of which can affect real test results.