Choosing the Right Diamond Size

Choosing the right diamond size can be confusing—especially when you’re trying to understand how millimeter (mm) measurements translate into carat (ct) weight. At Precious Carbon, we make it simple. Whether you’re selecting a diamond for your engagement ring, wedding band, or a custom jewelry piece, this guide helps you visualize diamond sizes in mm and carats. Use this as a reference to make confident decisions when shopping for your next diamond in the USA.

MM to Carat Conversion – What You Need to Know

Carat is a measure of diamond weight, while millimeter (mm) indicates the physical size. Two diamonds with the same carat weight may look different in size due to shape and cut proportions. That’s why it’s important to consider both carat and millimeter size when choosing a diamond.

Here’s a quick breakdown:
• MM (millimeters) = size (diameter / length & width)
• Carat (ct) = weight of the diamond
• Cut & shape affect how large a diamond appears

Why Understanding Diamond Size Matters

When shopping for a diamond, size isn’t just about carat weight. Understanding mm dimensions helps you:

• Get the look you want without overpaying
• Choose the right size for your ring setting
• Compare stones more accurately
• Ensure your diamond matches your budget and expectations

Tip: A well-cut 1.00 carat diamond (6.5 mm) may appear larger and more brilliant than a poorly cut 1.25 ct stone. Always check both carat and mm size before buying.

Whether you're new to diamonds or finalizing a purchase, this tool is your go-to diamond sizing reference. Still unsure? Reach out to our team—we offer free custom design consultations and are here to help you find your perfect fit.