Before you even start diamond shopping, you want to have a full understanding of what you're buying. This guide simplifies the four Cs of diamonds — cut, color, clarity, and carat weight, so you can select your diamond based on the same criteria jewelers use to grade them.

After reading through this guide, you'll be ready to choose the diamond that's right for you.

Before approaching the four Cs, we'd like to introduce you to the diamond certificate (also called a grading report). A grading report documents the characteristics of a diamond, including the four Cs, as noted by a gemologist or gemologists. Before purchasing a diamond, you should review a copy of its certificate, as this is your guarantee of the quality and value of that diamond.

The cut of a diamond has a tremendous affect on its brilliance. Even if the diamond has perfect color and clarity, a poor cut can make a diamond look dull. Blue Nile carries only the highest grades of diamond cut, which present the most beautiful brilliance.

Colorless diamonds are most highly valued and are priced accordingly. Other diamonds have a slight yellow tint, and some can even have a noticeable dirty brownish tint. Blue Nile offers only the highest grades of color, as slight yellow or brown tints can diminish the amount of fire in a diamond.

Diamonds completely free from internal flaws, or inclusions, are very rare and highly valued. Clarity is graded based on the number, location, size, and type of the inclusions found in a diamond. Blue Nile has some of the clearest diamonds available.

The weight of a diamond is measured in carats. Since larger diamonds are more rare than smaller diamonds, diamond value tends to rise exponentially with carat weight.