1.8 Carat Radiant (8×6×4.8mm) vs. 2.5 Carat Radiant (9×7×5.4mm)

Diamond comparison

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Actual size of 1.8ct Radiant diamond
Actual size
sample image
vs.
Actual size of 2.5ct Radiant diamond
Actual size
sample image
1.8 ct Radiant (8×6×4.8mm) 2.5 ct Radiant (9×7×5.4mm)
Cutting style
Mixed
Mixed
Weight
1.8 ct
2.5 ct
Measurements
8×6×4.8 mm
9×7×5.4 mm
Total depth
80% too deep!
77.1% too deep!
L/W ratio
1.33
1.29
Face-up size
Adequate
Adequate
 
This diamond LOOKS its weight!
This diamond LOOKS its weight!
Actual diamond size
Actual diamond size
Before purchasing a diamond, one should make sure it looks its weight. It's important to understand that carat weight does not equal face-up size.

Two diamonds of exactly the same weight (and shape) can vary quite considerably in face-up size. This depends on the proportions of the cut (e.g., deep cuts will face up smaller).

Here you can see the actual sizes of 1.8ct Radiant (8×6×4.8mm) and 2.5ct Radiant (9×7×5.4mm) as they would appear on a ring and finger.

Adjust the ring and finger size to get an idea of how these stones would look on your finger. To choose different diamonds or to change diamond parameters click here.

Compare prices and availability from recommended online vendors:


Settings
Ring: Skin tone:
Ring width: 3.0 mm
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Left finger image
Ring on a left finger
1.8ct Radiant on a left ring
64 mm
Right finger image
Ring on a right finger
2.5ct Radiant on a right ring
Your settings
Ring
Gold
Skin tone
Light
Ring diameter
16.9 mm
Ring width
3.0 mm
Finger length
64 mm
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Ring diameter: 16.9 mm
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1.8ct Radiant side view Side view of ring
vs
2.5ct Radiant side view Side view of ring
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Face-up area
45.6 mm²  (±4%)
59.85 mm²  (±4%)
Face-up area is a measure of the size of the diamond when viewed from the top (as set in a ring).

It tells you how big the diamond is at the girdle plane. It's important for a diamond to have sufficient face-up size for its carat weight.
Face-up size outline
Face-up size outline
1.8ct Radiant (8×6×4.8mm)
2.5ct Radiant (9×7×5.4mm)
Difference: 14.25mm² (31%)
2.5 carat Radiant (9×7×5.4mm) has approx. 31% more top surface area than 1.8 carat Radiant (8×6×4.8mm).
Face-up area per carat
25.33 mm²/ct
23.94 mm²/ct
To learn about the accuracy of these numbers, click here.

Quick Buying Guide

1.8ct Radiant (8×6×4.8mm)
2.5ct Radiant (9×7×5.4mm)
Min. clarity
SI or better
SI or better
Min. color (platinum solitaire)
H+
H+
Depth percentage
59 - 70%
59 - 70%
Table percentage
58 - 70%
58 - 70%
Length-to-width ratio
1.00 - 1.35
1.00 - 1.35
Min. polish/symmetry
Good or better
Good or better
 Detailed buying guide

Additional Info

1.8ct Radiant (8×6×4.8mm)
2.5ct Radiant (9×7×5.4mm)
Face-up size
Normal for 1.8 carat Radiant
Normal for 2.5 carat Radiant
Facets
usually between 62 - 70
usually between 62 - 70
Length
8 mm
9 mm
Width
6 mm
7 mm
Depth
4.8 mm
5.4 mm
Gram weight
0.36 g (0.0127 ounces)
0.5 g (0.0176 ounces)
Points
180 pts
250 pts
Volume
102.27 mm³
142.05 mm³


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Depth percentage for 1.8 carat Radiant (8×6×4.8mm)

Depth percentage of Radiant cut is the ratio of the total depth (measured from table to culet) to its width. The total depth percentage of this diamond is 80%, which is too deep!. (Recommended depth percentage for Radiants is between 59% and 70%)

Depth percentage for radiants is calculated with the following formula:
Depth % = (total depth ÷ width) × 100

1.8 carat Radiant (8×6×4.8mm) depth %:
Total depth: 4.8 mm
Width = 6 mm
Depth % = (4.8 ÷ 6 ) × 100 = 80%

Depth percentage for 2.5 carat Radiant (9×7×5.4mm)

Depth percentage of Radiant cut is the ratio of the total depth (measured from table to culet) to its width. The total depth percentage of this diamond is 77.1%, which is too deep!. (Recommended depth percentage for Radiants is between 59% and 70%)

Depth percentage for radiants is calculated with the following formula:
Depth % = (total depth ÷ width) × 100

2.5 carat Radiant (9×7×5.4mm) depth %:
Total depth: 5.4 mm
Width = 7 mm
Depth % = (5.4 ÷ 7 ) × 100 = 77.1%

About Depth Percentage
Depth percentage is one of the most important measurements as it plays a critical role in diamond's appearance. If a diamond is cut too deep or too shallow, light leaks out, making the stone less brilliant and fiery. Deep cuts also add hidden weight.

Diamonds that fall out of recommended depth range are generally less desirable and usually best to be avoided.


Face-up size evaluation for 1.8 carat Radiant (8×6×4.8mm)

The face-up size of this 1.8 carat Radiant (8×6×4.8mm) is within the normal range for 1.8ct diamonds of this shape. Compared to 1.8ct Radiant reference diamond (see below), this diamond is of adequate size when viewed from the top.

Diamonds are sold by weight (carats), but it's important to understand that weight doesn't equally translate into physical size, especially spread. Two diamonds of the same carat weight can vary greatly in spread, meaning that one diamond can appear larger than the other, even though they weight exactly the same.

Proper face-up size should play an important role when buying a diamond. When a diamond is set in a ring, your eyes will only see the face-up area, so you should make sure it's of adequate size. You probably don't want a 1.8 carat Radiant that looks like a poorly cut 1.62ct.

The bottom line: A diamond must look its weight. This one does.

1.8 carat Radiant reference diamond

Since there are no specific ideal proportions defined for Radiant cuts, an estimation formula is used to calculate the Radiant reference diamond.
Parameters:
Weight: 1.8ct
Depth: 64%
L/W ratio: 1
 
Calculated values:
Length: 7.03 mm
Width: 7.03 mm
Depth: 4.5 mm
*Est. face-up area: 46.95 mm²
Note: Radiant diamonds with face-up area of within 9% lower and 12% higher than reference Radiant diamond area are considered to be of adequate face-up size.
* Estimated Face-up area: Face-up area of Radiant cuts is only an estimation (±4%). Due to uniqueness of each stone, it's impossible to accurately calculate face-up area given only a diamond's measurements.
To learn more about diamond size evaluation, click here.


Face-up size evaluation for 2.5 carat Radiant (9×7×5.4mm)

The face-up size of this 2.5 carat Radiant (9×7×5.4mm) is within the normal range for 2.5ct diamonds of this shape. Compared to 2.5ct Radiant reference diamond (see below), this diamond is of adequate size when viewed from the top.

Diamonds are sold by weight (carats), but it's important to understand that weight doesn't equally translate into physical size, especially spread. Two diamonds of the same carat weight can vary greatly in spread, meaning that one diamond can appear larger than the other, even though they weight exactly the same.

Proper face-up size should play an important role when buying a diamond. When a diamond is set in a ring, your eyes will only see the face-up area, so you should make sure it's of adequate size. You probably don't want a 2.5 carat Radiant that looks like a poorly cut 2.25ct.

The bottom line: A diamond must look its weight. This one does.

2.5 carat Radiant reference diamond

Since there are no specific ideal proportions defined for Radiant cuts, an estimation formula is used to calculate the Radiant reference diamond.
Parameters:
Weight: 2.5ct
Depth: 64%
L/W ratio: 1
 
Calculated values:
Length: 7.84 mm
Width: 7.84 mm
Depth: 5.02 mm
*Est. face-up area: 58.39 mm²
Note: Radiant diamonds with face-up area of within 9% lower and 12% higher than reference Radiant diamond area are considered to be of adequate face-up size.
* Estimated Face-up area: Face-up area of Radiant cuts is only an estimation (±4%). Due to uniqueness of each stone, it's impossible to accurately calculate face-up area given only a diamond's measurements.
To learn more about diamond size evaluation, click here.


Face-up Area per Carat

Face-up area per carat is calculated by dividing face-up area of the diamond with its carat weight. It tells you how many square millimeters of the top surface area a diamond is showing or would show for 1 carat weight. This can be useful when comparing stones of similar weights as it tells you how much spread per carat you will get.

Note: Face-up size does not linearly grow with carat weight, which means the heavier the stone, the smaller its face-up area per carat (e.g., 1ct stone will have higher face-up area per carat than 2ct stone).

Face-up area per carat for 1.8ct Radiant (8×6×4.8mm):
Top surface area = 45.6 mm²
Weight = 1.8ct

Face-up area per carat = 45.6 ÷ 1.8 = 25.33mm²/ct

Face-up area per carat for 2.5ct Radiant (9×7×5.4mm):
Top surface area = 59.85 mm²
Weight = 2.5ct

Face-up area per carat = 59.85 ÷ 2.5 = 23.94mm²/ct

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