What Does Diamond Carat Weight Actually Mean?
Carat is one of the most misunderstood words in jewellery. Most people assume it means size, but it actually means weight. One carat equals 0.2 grams. That is it.
Why weight and size are not the same thing
Two diamonds can have the same carat weight but look completely different sizes depending on how they are cut. A well cut 0.9 carat diamond can appear larger than a poorly cut 1.1 carat stone because the proportions allow more light to reflect from the top surface.
This is why cut grade matters more than carat. A diamond with an excellent cut will always look more impressive than a heavier stone with a mediocre cut.
How carat affects price
Diamond prices do not scale linearly with carat weight. They jump at certain thresholds: 0.5ct, 1ct, 1.5ct and 2ct. A 0.98 carat diamond can be significantly cheaper than a 1.01 carat diamond even though the visual difference is undetectable. Buying just below these thresholds is one of the easiest ways to get better value.
With lab grown diamonds, the price difference is already substantial compared to mined. At Luma, a 1 carat lab grown diamond in an engagement ring will cost a fraction of what the same stone would cost from a traditional jeweller using mined diamonds.
What carat weight should you choose?
That depends on your budget and priorities. Our advice from the complete guide to lab grown diamonds: prioritise cut first, get colour and clarity to a point where imperfections are invisible, and then let carat weight follow whatever budget you have left.
A 0.7 carat diamond with an excellent cut and good colour will look better on the hand than a 1.2 carat diamond with a fair cut and visible warmth.
Popular carat ranges
For engagement rings, the most popular range is 0.8 to 1.5 carats. For everyday diamond jewellery like rings, necklaces and earrings, total carat weights vary widely depending on the design.
