8ct Pear (18.09×10.9×6.65) vs 1ct Princess (5.51×5.51×3.97)

Diamond size comparison

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Actual size of 8ct Pear diamond
Actual size
sample image
vs.
Actual size of 1ct Princess diamond
Actual size
sample image
8 ct Pear (18.09×10.9×6.65mm) 1 ct Princess (5.51×5.51×3.97mm)
Cutting style
Modified brilliant
Modified brilliant
Weight
8 ct
1 ct
Measurements
18.09×10.9×6.65 mm
5.51×5.51×3.97 mm
Total depth
61% OK
72.1% OK
L/W ratio
1.66
1
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 8ct Pear (18.09×10.9×6.65mm) and 1ct Princess (5.51×5.51×3.97mm) 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.
Settings
Ring: Skin tone:
Ring width: 3.0 mm
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Left finger image
Ring on a left finger
8ct Pear on a left ring
64 mm
Right finger image
Ring on a right finger
1ct 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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8ct Pear side view Side view of ring
vs
1ct Princess side view Side view of ring
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Face-up area
143.94 mm²  (±4%)
30.36 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
8ct Pear (18.09×10.9×6.65mm)
1ct Princess (5.51×5.51×3.97mm)
Difference: 113.58mm² (374%)
8 carat Pear (18.09×10.9×6.65mm) has approx. 374% more face-up area than 1 carat Princess (5.51×5.51×3.97mm).
Face-up area per carat
17.99 mm²/ct
30.36 mm²/ct
To learn about the accuracy of these numbers, click here.


Quick Buying Guide

Diamond prices vary greatly as they depend on the combination of unique characteristics (4Cs - Cut, Color, Clarity, and Carat). For best value, it's important to choose the combination that will reduce the price without having a negative impact on appearance.

Each shape has its own recommended balance of qualities that will give you the most bang for your buck. Below is a quick buying guide to give you an idea, but for more detailed explanation, please see the complete buying guides for the respective diamonds (links below).
8ct Pear (18.09×10.9×6.65mm)
1ct Princess (5.51×5.51×3.97mm)
Price (best value)
Min. clarity
SI or better
VS2, SI1 or better
Min. color (platinum setting)
H+
I+
Min. color (yellow gold setting)
J+
J+
Depth percentage
59 - 65%
64 - 75%
Table percentage
50 - 65%
60 - 75%
Length-to-width ratio
1.45 - 1.75
1.00 - 1.05
Min. polish/symmetry
Good or better
Good or better
 Detailed buying guide

Additional Info

8ct Pear (18.09×10.9×6.65mm)
1ct Princess (5.51×5.51×3.97mm)
Face-up size
Normal for 8 carat Pear
Normal for 1 carat Princess
Facets
usually 58
usually between 50 - 58
Length
18.09 mm
5.51 mm
Width
10.9 mm
5.51 mm
Depth
6.65 mm
3.97 mm
Gram weight
1.6 g (0.0564 ounces)
0.2 g (0.0071 ounces)
Points
800 pts
100 pts
Volume
454.55 mm³
56.82 mm³


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Depth percentage for 8 carat Pear (18.09×10.9×6.65mm)

Depth percentage of Pear cut is the ratio of the total depth (measured from table to culet) to its width. The total depth percentage of this diamond is 61%, which is OK. (Recommended depth percentage for Pears is between 59% and 65%)

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

8 carat Pear (18.09×10.9×6.65mm) depth %:
Total depth: 6.65 mm
Width = 10.9 mm
Depth % = (6.65 ÷ 10.9 ) × 100 = 61%

Depth percentage for 1 carat Princess (5.51×5.51×3.97mm)

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 72.1%, which is OK. (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

1 carat Princess (5.51×5.51×3.97mm) depth %:
Total depth: 3.97 mm
Width = 5.51 mm
Depth % = (3.97 ÷ 5.51 ) × 100 = 72.1%

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 8 carat Pear (18.09×10.9×6.65mm)

The face-up size of this 8 carat Pear (18.09×10.9×6.65mm) is within the normal range for 8ct diamonds of this shape. Compared to 8ct Pear reference diamond (see below), this diamond is of adequate size when viewed from the top. In short, all is OK, this diamond looks its weight.

The importance of face-up size
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. Adequate size also indicates a good cut, meaning better light performance. For example, if given a choice between a poorly cut 8 carat Pear with less sparkle and the same face-up size as a well cut 7.6ct Pear, which one would you choose?

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

8 carat Pear reference diamond
Since there are no specific ideal proportions defined for Pear cuts, an estimation formula is used to calculate the Pear reference diamond.
Parameters:
Weight: 8ct
Depth: 61%
L/W ratio: 1.66
 
Calculated values:
Length: 18.09 mm
Width: 10.9 mm
Depth: 6.65 mm
*Est. face-up area: 143.94 mm²
Note: Pear diamonds with face-up area of within 9% lower and 12% higher than reference Pear diamond area are considered to be of adequate face-up size.
* Estimated Face-up area: Face-up area of Pear 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.

Face-up size evaluation for 1 carat Princess (5.51×5.51×3.97mm)

The face-up size of this 1 carat Princess (5.51×5.51×3.97mm) is within the normal range for 1ct diamonds of this shape. Compared to 1ct Princess reference diamond (see below), this diamond is of adequate size when viewed from the top. In short, all is OK, this diamond looks its weight.

The importance of face-up size
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. Adequate size also indicates a good cut, meaning better light performance. For example, if given a choice between a poorly cut 1 carat Princess with less sparkle and the same face-up size as a well cut 0.9ct Princess, which one would you choose?

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

1 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: 1ct
Depth: 72%
L/W ratio: 1
 
Calculated values:
Length: 5.51 mm
Width: 5.51 mm
Depth: 3.97 mm
Face-up area: 30.36 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.

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 8ct Pear (18.09×10.9×6.65mm):
Top surface area = 143.94 mm²
Weight = 8ct

Face-up area per carat = 143.94 ÷ 8 = 17.99mm²/ct

Face-up area per carat for 1ct Princess (5.51×5.51×3.97mm):
Top surface area = 30.36 mm²
Weight = 1ct

Face-up area per carat = 30.36 ÷ 1 = 30.36mm²/ct

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