The term Carat very well elucidates what it represents. Carat is the standardised measure of a diamond’s weight. It is to be noted that any two diamonds with the same carat weight cannot be assumed to have the same size as well. A diamond’s weight is commonly but falsely perceived as a reflection of its size. The distribution of weight and the quality of the diamond’s cut are two important determinants of its size. It is always recommended to keep a balance between the cut and the carat weight of a diamond because a cut aimed primarily at maximising the carat weight of the diamond will result in deteriorating the sparkle of the stone which is dependent of the quality of the cut. A balance in cut-carat proportion is thus ideal for an enchanting diamond.A metric “carat” is defined as 200 milligrams. Each carat is subdivided into 100 ‘points.’ This allows very precise measurements to the hundredth decimal place. A jeweller may describe the weight of a diamond below one carat by its ‘points’ alone. For instance, the jeweller may refer to a diamond that weighs 0.25 carats as a ‘twenty-five pointer.’ Diamond weights greater than one carat are expressed in carats and decimals. A 1.08 carat stone would be described as ‘one point oh eight carats. All else being equal, diamond price increases with diamond carat weight because larger diamonds are rarer and more desirable. However, two diamonds of equal carat weight can have very different values (and prices) depending on three other factors of the diamond 4Cs mention below and it’s also important to remember that a diamond’s value is determined using all of the 4Cs, and not just carat weight.

  • Cut

  • Colour

  • Clarity

  • Carat

There exists a relationship between a diamond’s cut and its carat weight which is significant in understanding that there exists a trade-off between stunning sparkle and heaviness of a diamond stone. If a diamond cut is aimed at increased weight then the final stone is much likely to have a lower cut grade than it would normally have. Large diamonds having poor quality cut grades are simply not worth the value because they have a diminished sparkle. Sparkle is basically the light performance of the diamond, if the diamond’s cut is not appropriate the light leaks out from the sides and bottom of the stone instead of reflecting out from its top. Light leakage downgrades the light performance of the diamond, put simply it diminishes the sparkle. It is advisable to have balanced caret-cut proportion so that the diamond has an appropriate weight to compliment good quality light performance. A diamond that is too shallow or too deep has a low quality cut grade which should be avoided.

The Carat System

In order to understand what a diamond carat measures, it would help to know the origins of the modern carat system. Carat weight started with the carob seed, when early gem traders used the small, uniform seeds as counterweights in their balance scales. Today, the carat is the same milligram weight in every corner of the world.

A Diamond Carat Weight

A 1 carat (or ct) diamond weighs 0.20 grams. Contrary to popular belief, the carat is not the size of the diamond. A diamond's size is measured in millimetres, length by width — in other words, the diameter of the diamond. It typically takes about 250 tons of rock mining to produce a single 1 carat diamond. That's why diamonds are rare and expensive.

Diamonds come in a variety of shapes and carat weights. A diamond cutter’s highest priority is to maximise carat weight. The larger the diamond, the rarer and therefore more expensive it is. Diamonds are weighed very precisely, to the nearest 0.01ct.

Before universal adoption of the carat in 1907, a variety of measurements were used for diamonds. (At one point carob seeds were used, because it was believed — incorrectly — that the mass of each seed didn't vary much.) Over time, carat weight became standardised. It's now a common point of reference on the certificate of any diamond, regardless of which institution certifies it.

Diamond Carat Weight & Price Impact

Diamond pricing increases exponentially — not linearly — as diamond carat weight increases. That means once a diamond hits it’s critical weight, the price bumps up.

The critical weights are 0.30ct, 0.40ct, 0.50ct, 0.70ct, 0.90ct 1.00ct, 1.50ct, 2.00ct, 3.00ct, 4.00ct, 5.00ct and 10.00ct.

CARAT WEIGHT 1.00 2.00 3.00
PRICE / CARAT £4000.00 £5200.00 £25000.00
TOTAL PRICE £4000.00 £10400.00 £75000.00

Popular Carat Weights Ffor Diamonds

Carat has been the standard measure of gemstone weight for centuries. The mass value of carat is taken in milligrams. The modern standard which was set in 1907 defines carat in terms of milligrams only, one carat equals two hundred milligrams as explained above. Diamonds are available in various carat weights, the most popular weight range being from one carat to approximately two carats. Diamonds as heavy as five carats and as light as 0.25 carats are sold in the market. Shoppers’ popular choice has been studied to be one carat diamonds with round cut. The diamonds with step-cut shapes such as the emerald cut tend to have slightly higher weights than other forms because of the broader table dimensions of these. The depth percentage of step-cut shapes are also larger as compared to round cuts. Also the shapes such as the pear or the marquise tend to have larger surface areas as compared to other shapes for the same weight on the carat scale. These shapes are recommended for those who fancy larger looking stones with balanced cut-carat weights in a given budget.A quick tip on selecting the most appropriate diamond for your engagement ring or other jewels is to always keep your cut preference in sync with the carat. A diamond’s true beauty lies in its brilliance not heaviness. A cut-carat balance is thus important.


The carat is the standard unit of measurement used to indicate the weight of a diamond. Carat is often confused with size even though it is actually a measure of weight. One carat equals 200 milligrams or 0.2 grams. Remember that while the measurements below are typical, every diamond is unique. The scale below illustrates the typical size relationship between diamonds of increasing carat weights.

Understand “Magic Sizes’

You can save quite a bit of money on your engagement ring if you're wary of "magic sizes"— the numbers that cost more just because they're in demand, or a critical weight. Although there's no visual difference between a 1.99ct diamond and a 2.00ct, the 2.00ct can cost far more because it's a magic size. Diamonds that aren’t these “magic sizes” are called “off-size diamonds,” and they just might be the key to getting the engagement ring of your dreams.

Round Diamond Size Chart

Depending on the size of your round cut diamond, there are varying colour and clarity grades that will have implications on diamond sparkle. We’ve made a chart to quality these ranges.

Round Diamond Sizes & Carat Weight
0.8 0.0025 7 1.30
1 0.005 7.3 1.50
1.15 0.0067 7.5 1.67
1.12 0.0075 7.75 1.75
1.25 0.01 8 2.00
1.3 0.01 8.25 2.11
1.5 0.015 8.5 2.43
1.75 0.02 8.7 2.50
1.8 0.025 9 2.75
2 0.03 9.1 3.00
2.25 0.04 9.5 3.35
2.5 0.06 9.75 3.61
2.75 0.08 10 3.87
3 0.11 10.25 4.16
3.25 0.14 10.5 4.41
3.5 0.17 10.75 4.57
3.75 0.21 11 4.91
4 0.25 11.25 5.49
4.25 0.28 11.5 5.85
4.5 0.36 12 6.84
4.75 0.44 12.25 7.26
5 0.50 12.5 7.36
5.25 0.56 12.75 7.52
5.5 0.66 13 8.51
5.75 0.75 13.5 9.53
6 0.84 14 10.49
6.25 0.93 15 12.89
6.5 1.00 16 16.06
6.8 1.25 17 18.00

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