0.18 Carat Round (3.5×3.5×2.11mm) vs. 0.18 Carat Princess (3.5×3.5×2.11mm)

Diamond comparison

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Actual size of 0.18ct Round diamond
Actual size
sample image
vs.
Actual size of 0.18ct Princess diamond
Actual size
sample image
0.18 ct Round (3.5×3.5×2.11mm) 0.18 ct Princess (3.5×3.5×2.11mm)
Cutting style
Brilliant
Modified brilliant
Weight
0.18 ct
0.18 ct
Measurements
3.5×3.5×2.11 mm
3.5×3.5×2.11 mm
Total depth
60.3% OK
60.3% too shallow!
L/W ratio
1
1
Face-up size
Inadequate
Inadequate
 
This diamond does NOT look its weight!
This diamond is a SPREAD CUT!
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 0.18ct Round (3.5×3.5×2.11mm) and 0.18ct Princess (3.5×3.5×2.11mm) 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.

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Settings
Ring: Skin tone:
Ring width: 3.0 mm
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Left finger image
Ring on a left finger
0.18ct Round on a left ring
64 mm
Right finger image
Ring on a right finger
0.18ct Princess 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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0.18ct Round side view Side view of ring
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0.18ct Princess side view Side view of ring
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Face-up area
9.62 mm² 
12.25 mm² 
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
0.18ct Round (3.5×3.5×2.11mm)
0.18ct Princess (3.5×3.5×2.11mm)
Difference: 2.63mm² (27%)
0.18 carat Princess (3.5×3.5×2.11mm) has approx. 27% more top surface area than 0.18 carat Round (3.5×3.5×2.11mm).
Face-up area per carat
53.44 mm²/ct
68.06 mm²/ct
To learn about the accuracy of these numbers, click here.

Quick Buying Guide

0.18ct Round (3.5×3.5×2.11mm)
0.18ct Princess (3.5×3.5×2.11mm)
Min. clarity
SI or better
VS2, SI1 or better
Min. color (platinum solitaire)
J+
I+
Depth percentage
58 - 62.5%
64 - 75%
Table percentage
53 - 58%
60 - 75%
Length-to-width ratio
1.00 - 1.02
1.00 - 1.05
Min. polish/symmetry
Good or better
Good or better
 Detailed buying guide

Additional Info

0.18ct Round (3.5×3.5×2.11mm)
0.18ct Princess (3.5×3.5×2.11mm)
Face-up size
Too small for 0.18 carat Round
Too large for 0.18 carat Princess
Facets
58 (57 if no culet)
usually between 50 - 58
Length
3.5 mm
3.5 mm
Width
3.5 mm
3.5 mm
Depth
2.11 mm
2.11 mm
Gram weight
0.04 g (0.0013 ounces)
0.04 g (0.0013 ounces)
Points
18 pts
18 pts
Volume
10.23 mm³
10.23 mm³


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Depth percentage for 0.18 carat Round (3.5×3.5×2.11mm)

Depth percentage of Round cut is the ratio of the total depth (measured from table to culet) to its average diameter. The total depth percentage of this diamond is 60.3%, which is OK. (Recommended depth percentage for Rounds is between 58% and 62.5%)

Depth percentage for rounds is calculated with the following formula:
Depth % = (total depth ÷ average diameter) × 100

0.18 carat Round (3.5×3.5×2.11mm) depth %:
Total depth: 2.11 mm
Average diameter = (3.5 + 3.5) ÷ 2 = 3.5 mm
Depth % = (2.11 ÷ 3.5 ) × 100 = 60.3%

Depth percentage for 0.18 carat Princess (3.5×3.5×2.11mm)

Depth percentage of Princess cut is the ratio of the total depth (measured from table to culet) to its width. The total depth percentage of this diamond is 60.3%, which is too shallow!. (Recommended depth percentage for Princesses is between 64% and 75%)

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

0.18 carat Princess (3.5×3.5×2.11mm) depth %:
Total depth: 2.11 mm
Width = 3.5 mm
Depth % = (2.11 ÷ 3.5 ) × 100 = 60.3%

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 0.18 carat Round (3.5×3.5×2.11mm)

The face-up size of this 0.18 carat Round (3.5×3.5×2.11mm) is out of normal range for 0.18ct diamonds of this shape. A well cut 0.18ct Round should have an average diameter between 3.58 and 3.73 mm. Compared to 0.18 carat Round reference diamond, this diamond appears too small when viewed from the top, which makes it a chubby.

A chubby is a diamond with hidden extra weight that looks smaller than it should when viewed from the top. Hidden weight is typically a result of a poor cut usually linked to oversized girdle, deeper pavilion, and/or steeper crown.

In order to maximize profits, diamond cutters tend to retain as much weight from the rough as possible. This practice, however, can have detrimental effects on the stone's face-up size and its optical qualities. Poorly proportioned stones look duller and sparkle less than well cut stones. Chubby stones also look smaller.

The bottom line: One should never sacrifice beauty for weight. You probably don't want to pay for extra weight that doesn't add anything to the beauty. You want a stone that looks its weight. This one doesn't - it looks like a well cut 0.16ct Round.

0.18 carat Round reference diamond

0.18ct Round reference diamond is calculated from the following ideal proportions:
Proportions:
Table: 57%
Crown angle: 34°
Pavilion angle: 40.7°
Girdle: 2.8%
Star length: 50%
Lower half-length: 80%
Culet: None
 
Calculated values:
Depth: 60.3%
Crown height: 14.5%
Pavilion height: 43%
For 0.18 carat weight:
Diameter: 3.67 mm
Face-up area: 10.58 mm²
Note: Round diamonds with face-up area of within 5% lower and 3% higher than reference Round diamond area are considered to be of adequate face-up size.
To learn more about diamond size evaluation, click here.


Face-up size evaluation for 0.18 carat Princess (3.5×3.5×2.11mm)

The face-up size of this 0.18 carat Princess (3.5×3.5×2.11mm) is out of normal range for 0.18ct diamonds of this shape. Compared to 0.18 carat Princess reference diamond, this diamond appears too big when viewed from the top. You might think that's a good thing, however, it's not. This is a so called spread cut.

A spread cut is a diamond that is cut to maximize spread. It looks larger than a well-cut 0.18ct Princess when viewed from the top, however, this is not a good thing. Spread cuts are typically too shallow, which allows light to leak out of the stone instead of being properly returned back to the viewer's eye.

Spread cuts usually look lifeless and flat, and can sometimes exhibit a fish-eye effect. They may also come with an extremely thin girdle which can easily chip.

The bottom line: Spread cuts generally lack the brilliance and perfection that is expected of a beautiful diamond. Don't be fooled into thinking that you're getting a larger diamond for the money. This could be a rather flat, boring stone.

0.18 carat Princess reference diamond

Since there are no specific ideal proportions defined for Princess cuts, an estimation formula is used to calculate the Princess reference diamond.
Parameters:
Weight: 0.18ct
Depth: 72%
L/W ratio: 1
 
Calculated values:
Length: 3.11 mm
Width: 3.11 mm
Depth: 2.24 mm
Face-up area: 9.67 mm²
Note: Princess diamonds with face-up area of within 8% lower and 12% higher than reference Princess diamond area are considered to be of adequate face-up size.
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 0.18ct Round (3.5×3.5×2.11mm):
Top surface area = 9.62 mm²
Weight = 0.18ct

Face-up area per carat = 9.62 ÷ 0.18 = 53.44mm²/ct

Face-up area per carat for 0.18ct Princess (3.5×3.5×2.11mm):
Top surface area = 12.25 mm²
Weight = 0.18ct

Face-up area per carat = 12.25 ÷ 0.18 = 68.06mm²/ct

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