Diamond vs Gemstone Carat Size: Why They’ll Never Look the Same

When shopping for an engagement ring or fine jewellery piece, it’s easy to assume that carat weight is the ultimate way to compare size. But here’s the ultimate secret… a carat is a “weight measurement” not a “size measurement” and when it comes to coloured gems versus diamonds (natural or lab), that difference really does matter.

Lets take a look at the variables. 

*Carat Weight vs. Visual Size*

A diamond and a sapphire (for example) may both weigh 1 carat, but they won’t look the same size visually. Why? Because gem all have different densities.

~  Diamonds are relatively light in density for their size, meaning a 1ct diamond will appear larger than a 1ct sapphire.

~ Sapphires, rubies, and emeralds are denser than other gems  — so a 1ct sapphire can actually look smaller than a 1ct diamond.

That’s why comparing a diamond and a coloured gemstone purely by carat weight can be misleading and ultimately dissapointing if you’re not a really seeing the stones in person or requesting actual mm size. 

*Depth, Cut, and Proportions Matter*

Another reason size perception changes is due to stone depth. This is one of the considerations I factor in the most as this will also impact the overall height of the jewellery design you select.  

Coloured gemstones are often cut deeper than diamonds to maximise their colour, depth of hue and brilliance. Diamonds, on the other hand, are cut for light performance — with more standardised proportions.

So while your sapphire may weigh more on the scales, much of that weight is “hidden” below the setting, whereas a diamond’s spread across the top may make it appear larger. 

At Leskes Jewellers, we help you understand these differences so you’re not comparing apples to oranges.

*The Better Way to Judge Coloured Stones*

Instead of focusing purely on carat weight, we look at millimetre measurements (length × width × depth). These give you a true indication of how large a coloured gemstone will appear once set in a ring or pendant.

note: carat weight and mm measurements are just one of many variables and elements that  make up the selection of a stone? It is by no means the only one. 

For example:

• A 1.50ct  round brilliant cut diamond may face up with a “spread” of 7.5mm.

• A 1.50ct round sapphire may only face up with a “spread” of 6.2 - 6.5mm

This 1mm may not seem much in your mind but visually - it’s alot! 6.4 mm is the approximate size of a nice 1.0 carat diamond 

Same weight, different visual presence.

*Why This Matters for You*

When investing in a gemstone — whether a diamond engagement ring or a coloured stone ring — it’s important to know exactly what you’re selecting. You deserve to understand how your stone will look on your hand, not just what the numbers say.

At Leskes Jewellers,  Peregian Beach, we specialise in helping you compare stones side by side, explaining not only the carat weight but also how cut, depth, and proportions affect what you see. It’s this expert guidance that ensures your final choice matches your vision and feels uniquely yours.

Trust Leskes Jewellers as Your Diamond & Gemstone Specialists

We know gemstones aren’t one-size-fits-all — and neither is fine jewellery shopping. That’s why our valued clients come to Leskes Jewellers for trusted advice, transparent sourcing, and custom design expertise.

Whether you’re considering a classic diamond solitaire or a coloured gemstone statement ring, we’ll guide you through the details so your sparkle tells the story you want it to.

✨ Your forever piece deserves more than just a number.

Visit us at Leskes Jewellers Peregian Beach to discover your perfect diamond or coloured gem. 

✨ Don’t get caught up in the carat trap. Let us help you choose the stone that’s perfect for you — in brilliance, size, and story.

📍 Visit Leskes Jewellers Peregian Beach and start your forever with the right sparkle.