Diamond Carat
Diamond Fundamentals

Diamond Carat

What is diamond carat weight and how does this determine price? Find out which diamond carat weight might be right for you and your budget with this detailed diamond carat guide, written and curated by our expert gemmologists.
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What is diamond carat?

Carat is a measurement of a diamond’s weight, and is reflective of the size of the stone. Two diamonds of the same carat weight can appear different sizes depending on the shape and how well the diamond is cut, but generally speaking, carat is a good indicator of a diamond's size. Referred to in short-form as ‘ct’, carat is a unit of measurement used for diamonds and other precious gemstones, like rubies, sapphires and emeralds, equating to 0.20g.

How and when did the carat system start?

The word ‘carat’ comes from the word ‘carob’. Carob seeds were found to have consistent weighting, around 0.20g, and were used to counterbalance the scales of gem traders in ancient times. 1ct of diamond weighs 0.20g, just as the carob seed does - although the scales used to weigh diamonds these days are highly accurate!

How does carat weight affect diamond size?

The higher the carat weight of a diamond, the larger it is. That said, not all equally-weighted diamonds will look the same - because of differences in diamond shapes dimensions, diamond cut quality, and of course each diamond’s unique makeup. However, it is possible to roughly estimate the size of a diamond based on its carat weight.

How does a diamond's carat weight affect its price?

The price of diamonds increases exponentially with weight and diamond price points can jump by large increments depending on carat weight. Larger diamonds are much rarer, so the value of one large stone will be far greater than two smaller diamonds that amount to the same total carat weight. Use our diamond carat vs price table below to see how diamond price increases with carat, and note the price jumps at certain weights, like 1ct. We've included lab diamonds vs natural diamonds prices.
Note, prices are accurate at time of writing and are subject to market fluctuations Rather than choose an ideal carat weight you’d like to buy, you may prefer todefine your budget, prioritise the cut and colour grade which have the biggest visual impact, then consider clarity. After that, you can see which carat sizes work to your budget, rather than strechting your budget to reach a certain carat. You’ll probably find a selection of quality diamonds within a range of 0.10ct that will work for your personal budget, for example 0.60 to 0.70ct, or 0.90 to 1ct.

What are the magic numbers of diamond carats?

In diamond carat weight, magic numbers are the points that diamond prices can jump significantly.The magic numbers in diamond carat weight are typically found in 0.25ct increments: 0.50ct, 0.75ct, 1ct, 1.25ct, 1.50ct, 1.75ct, 2ct, and so on. This means a 0.97ct diamond, for example, will be significantly cheaper than a 1ct diamond. The most significant price jumps are at 1ct increments. There are other carat weights that can see slightly less significant but still notable price increases, like 0.90ct.

How can ‘undersized diamonds’ save you money?

Standard carat weights rise in particular increments, with industry standard cut-off weights such as 0.50ct, 0.75ct, 1ct, and so on - these are known as the ‘magic numbers’. Diamond prices can jump significantly with these carat points and most diamond cutters will aim for these weights. If you find a diamond that just falls short of a magic number, it can be great value for money - for example, the visible size difference between a 0.97ct and 1ct diamond will be negligible, but the price difference significant.

What does TCW mean in relation to diamonds?

As well as an individual gemstone’s carat weight, jewellers often refer to ‘total carat weight’ (which shortens to 'tcw'). This is the combined weight of all diamonds or other gems that are included in a single piece of jewellery. For example, a diamond halo engagement ring’s total carat weight would include the central stone and those surrounding it, and a pair of diamond earrings would have their total carat weight calculated from both earrings in the set.

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