Oww I think I grasp what my mistake was on the calculation.

I did a new calculation and used the following

calculator with the 'LEDs in Series' formula. I used the following inputs:

Supply Voltage: 18v

Forward voltage: 1.8v

Desired LED Current: 20 mA

How many leds connected: 8

I based the supply voltage on 18v because 8 * 1.8 = 14.4v

So 14.4 voltage is required to power up each LED.

However 18v will give each LED a current of 20mA instead of 18mA with 16v.

The output of the calculation:

180 Ohms and 1/8 watts

I am on the right track now? and if yes, how do I convert the 5v to 18v?