# How to Calculate and Solve for Knoop Hardness Number | Mechanical Properties

The image above represents knoop hardness number. To calculate knoop hardness number, two essential parameters are needed and these parameters are Load Applied (P)Â andÂ Length of Indenter Tip (l).

### The formula for calculating knoop hardness number:

HK =Â 14.2P/lÂ²

Where:

HK = Knoop Hardness Number
l = Length of Indenter Tip

Given an example;
Find the knoop hardness number when the load applied is 21 and the length of indenter tip is 3.

This implies that;

P = Load Applied = 21
l = Length of Indenter Tip = 3

HK =Â 14.2P/lÂ²
That is, HK = 14.2(21)/(3)Â²
HK =Â (298.2)/(9)
HK = 33.13

Therefore, theÂ knoop hardness numberÂ isÂ 33.13.

### Calculating the Load Applied when the Knoop Hardness Number and the Length of Indenter Tip are Given

P = HK(l2) / 14.2

Where:

HK = Knoop Hardness Number
l = Length of Indenter Tip

Let’s solve an example;
Given that, the knoop hardness number is 14 and the length of indenter tip is 2. Find the load applied?

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This implies that;

HK = Knoop Hardness Number = 14
l = Length of Indenter Tip = 2

P = HK(l2) / 14.2
P = 14(22) / 14.2
So, P = 14(4) / 14.2
P = 56 / 14.2
P = 3.94

Therefore, theÂ load appliedÂ isÂ 3.94.

### Calculating the Length of Indenter Tip when the Knoop Hardness Number and the Load Applied are Given

l = âˆš14.2P / HK

Where:

l = Length of Indenter Tip
HK = Knoop Hardness Number

Let’s solve an example;
Find the length of indenter tip when the knoop hardness number is 8 and the load applied is 6.

This implies that;

HK = Knoop Hardness Number = 8
P = Load Applied = 6

l = âˆš14.2P / HK
l = âˆš14.2 (6) / 8
So, l = âˆš85.2 / 8
l = âˆš10.65
l = 3.26

Therefore, theÂ length of indenter tip isÂ 3.26.

### How to Calculate Knoop Hardness Number With Nickzom Calculator

Nickzom Calculator â€“Â The Calculator Encyclopedia is capable of calculating the knoop hardness number.

To get the answer and workings of the knoop hardness number using the Nickzom Calculator â€“ The Calculator Encyclopedia.Â First, you need to obtain the app.

You can get this app via any of these means:

You can also try theÂ demoÂ version viaÂ https://www.nickzom.org/calculator

Apple (Paid)Â â€“Â https://itunes.apple.com/us/app/nickzom-calculator/id1331162702?mt=8
Once, you have obtained the calculator encyclopedia app, proceed to theÂ Calculator Map,Â then click onÂ Materials and MetallurgicalÂ underÂ Engineering.

Now, Click onÂ Mechanical PropertiesÂ underÂ Materials and Metallurgical

Now, Click on Knoop Hardness NumberÂ underÂ Mechanical Properties

The screenshot below displays the page or activity to enter your values, to get the answer for the knoop hardness number according to the respective parameter which is the Load Applied (P)Â andÂ Length of Indenter Tip (l).

Now, enter the values appropriately and accordingly for the parameters as required by the Load Applied (P) is 21 and Length of Indenter Tip (l) is 3.

Finally, Click on Calculate

As you can see fromÂ the screenshot above,Â Nickzom Calculatorâ€“ The Calculator Encyclopedia solves for the knoop hardness number and presents the formula, workings and steps too.