Free Vickers Hardness Number Calculator

What Is the Vickers Hardness Number Calculator?

The Vickers hardness number calculator is a free online HV calculator that returns a material's hardness from the dimensions of a single indentation. As part of the widely used Vickers hardness scale (introduced in 1921), this method serves as a convenient alternative to the Brinell test: the result is independent of the indenter diameter, making the procedure simpler to perform. Whether you need a quick assessment for quality control or in‑depth materials research, this material hardness calculator provides instant, accurate HV values once you supply the indentation measurements.

Understanding the Vickers Hardness Test

Hardness tests evaluate how well a material resists permanent deformation. In the Vickers method, a diamond indenter ground to a precise pyramid shape with a face angle of $136^\circ$ is forced into the specimen under a known load $F$ (typically applied for 10–15 s). After the load is removed, the square‑pyramid indentation is measured: both diagonals are recorded and averaged to yield the mean diagonal $d$ (in millimeters). The entire procedure and the calculation of hardness are governed by the international standard ISO 6507 (BS EN ISO 6507‑1).

Why Choose the Vickers Scale?

Unlike the Brinell or Rockwell tests, the Vickers test uses a single indenter for all materials, from soft metals to very hard ceramics. This consistency, along with the unambiguous relationship between indentation size and hardness, makes the Vickers scale particularly valuable for research and for testing thin sections or surface‑treated layers.

The Vickers Hardness Number Formula

The Vickers hardness number (HV) – expressed in $\text{kgf/mm}^2$ – is derived from the formula:

$$HV = \frac{2F \sin(\alpha/2)}{g\,d^2}$$

where
$F$ = applied load in newtons (N),
$\alpha$ = indenter angle = $136^\circ$,
$d$ = mean diagonal length (mm),
$g$ = gravitational acceleration = $9.80665\ \text{m/s}^2$.

The factor $g$ converts the force from newtons to kilogram‑force, ensuring the result is in the traditional HV unit.

Conversion to MPa and GPa

To obtain the surface area hardness $H$ in megapascals, simply multiply the HV value by $g$:

$$H_{\text{MPa}} = HV \times g$$

If you need the result in gigapascals, divide by 1000:

$$H_{\text{GPa}} = \frac{HV \times g}{1000}$$

Estimating Tensile Strength

For many metallic crystalline materials, the Vickers hardness number can be used to approximate the ultimate tensile strength (UTS). A common rule‑of‑thumb relationship is:

$$UTS \approx \frac{HV}{c}$$

with the constant $c$ close to $3$. Therefore, $UTS \approx H_{\text{MPa}} / 3$.

A Step‑by‑Step Example with the HV Calculator

Assume a test where the load is $50\ \text{N}$ and the average diagonal of the indentation is $0.5\ \text{mm}$.

1. Enter $F = 50\ \text{N}$ and $d = 0.5\ \text{mm}$ into the Vickers hardness test calculator.
2. The tool applies the formula:

$$HV = \frac{2 \times 50 \times \sin(68^\circ)}{9.80665 \times (0.5)^2} = \frac{100 \times 0.92718}{9.80665 \times 0.25} = \frac{92.718}{2.45166} \approx 37.8$$

3. From the HV value, it computes the surface area hardness:

$$H_{\text{MPa}} = 37.8 \times 9.80665 \approx 370.9\ \text{MPa}$$

4. Finally, it estimates the tensile strength:

$$UTS \approx \frac{370.9}{3} \approx 126.06\ \text{MPa}$$

The calculator performs all these steps instantly, allowing you to obtain results with just a few inputs.

How Vickers Hardness Numbers Are Reported

The standardized notation for a Vickers hardness number is xxxHVyy or xxxHVyy/zz, where:

• $xxx$ is the hardness value (in $\text{kgf/mm}^2$),
• $yy$ denotes the test load in kilogram‑force,
• $zz$ indicates the dwell time in seconds if it differs from the standard 10–15 s.

For example, a result of 400 HV30 means a hardness of 400 kgf/mm² obtained under a load of 30 kgf.

Typical HV Ranges for Common Materials

Although actual values depend on composition and heat treatment, approximate ranges include:

• Iron: 30–80 HV5
• Carbon steel: 55–120 HV5
• Aluminum alloys: 15–60 HV5 (varies widely with alloy and temper)
• Copper: 40–110 HV5

These benchmarks can help you quickly gauge whether your test result falls within an expected window.