You will hear the term “eye clean” used a lot regarding clarity. Eye clean simply means that the diamond’s inclusions are too small to see without any aid such as a magnification glass.
To maximise your spending budget, a clarity grade of Slightly Included (SI) and Very Slightly Included (VS) grades are great as the inclusions within these diamonds will not be easily noticeable without any magnification.
Clarity is deemed slightly less important than a diamond’s cut or colour as cut, or colour is more noticeable than clarity to the naked eye.
A diamond’s shape and size can affect clarity. If you are planning on buying any diamond over one carat or even fancy-shaped diamonds, like an emerald or Ascher cut, you may need to get a higher clarity grade as flaws are more visible in bigger diamonds and fancy-shaped diamonds.
Diamond clarity can affect a diamond’s beauty although you don’t need to get the highest high clarity grade to avoid seeing imperfections with the naked eye.

Diamond Clarity Factors to consider:

• Size: The larger or more noticeable inclusion is in a diamond, then likely the lower the clarity grade is for that diamond.
• The number of inclusions: The more inclusions and blemishes easily seen, the lower the clarity grade. Similarly, the fewer inclusions easily seen means the higher the clarity grade the more expensive the diamond.
• Position of inclusions: notice the position of the inclusions. If the blemish is right under the table and closer to the pavilion (see the anatomy of diamonds to understand where a table and pavilion are located on a diamond), then this turns the inclusion into a reflector which would impact its clarity grade.
• Nature and type of inclusion: the nature and type of diamond inclusion could impact the durability of the diamond.
• Great value diamonds: To get a great value diamond with great clarity, aim for a VS or a SI diamond. Many inclusions are too small to be seen by the naked eye and require a loupe and a trained diamond grader to even see the inclusion. To the everyday naked eye, an eye that is not using a loupe or microscope, a graded VS1 and an SI2 diamond could very well look the same.
  However, VS1 and SI2 diamonds are quite different in quality and price point. For the best value, pick a diamond with inclusions that can’t be seen from the top down without magnification. These are referred to as eye-clean diamonds. Eye-clean diamonds are much more valuable for money as they are less expensive and look the same as the higher grades to the naked eye.

Diamond Clarity and Diamond Shape: Fancy and step-cut diamonds, like Emerald and Ascher, require higher clarity grades due to their rectangular facets that highlight transparency and make inclusions visible. For step-cut diamonds, a clarity grade of VS1 or higher is recommended to avoid visible inclusions. On the other hand, shapes like round, princess, oval, marquise, pear, and heart, which have a brilliant facet pattern, can have a lower clarity grade as they naturally hide inclusions due to the reflection of light from multiple angles.

Diamond Clarity and Diamond Size: The bigger the diamond, the easier it is to see inclusions. For bigger diamonds it is important to factor in higher clarity grades, so imperfections are not easily seen within the diamond.