Once you've determined what cut, color, and clarity grade you're looking for in a diamond, it's easy to determine the carat weight of diamond that will fit within your budget.

When diamonds are mined, large gems are discovered much less frequently than small ones, which makes large diamonds much more valuable. In fact, diamond prices rise exponentially with carat weight. So, a 2-carat diamond of a given quality is always worth more than two 1-carat diamonds of the same quality.

• If you have a set budget, explore all your options and you'll find that there is a wide range of diamond carat weights and qualities available in your price range.
• Also keep in mind that the smaller the finger, the larger the diamond will appear. A 1½-carat diamond solitaire looks much larger on a size 4 finger than a size 8.
• If you have already chosen a setting, to make sure you choose a diamond to fit, look for the diamond size specifications of your ring in the product catalog or ask your customer service associate what size diamond you should look for.
• Finally, if a large carat weight is important to you, yet you're working within a budget, consider a diamond with a good cut, SI1 to I1 clarity, and an I to K color grade.

But the best way to determine what size is best is by getting an idea of what she is expecting. If you plan carefully, you can get some answers without even raising her suspicions.