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4ct Sapphire (Round, 9.49×9.49mm, Blue) vs 4ct Diamond (Round, 10.32×10.32mm, White)


Quick summary: When looked from above (face-up position), 4ct Diamond (10.32×10.32mm, round cut) appears 18% larger than 4ct Sapphire (9.49×9.49mm, round cut). See below how they compare side-by-side on a ring and finger.

4ct Sapphire (round cut)
vs
 4ct Diamond (round cut)
blue
 
white
9.49×9.49 mm 10.32×10.32 mm
actual size
Actual size of 4ct Sapphire (round cut, 9.49×9.49mm, Blue color)   Actual size of 4ct Diamond (round cut, 10.32×10.32mm, White color)
 
Actual size is set for screen
Ring: Skin tone:
Ring width: 3.0 mm
Left finger image
Ring on left finger
Blue 4ct Sapphire (round cut, 9.49×9.49mm) on a left ring and finger
64 mm
Right finger image
Ring on a right finger
White 4ct Diamond (round cut, 10.32×10.32mm) on a right ring and finger
Your settings
Ring
 Gold
Skin tone
 Light
Ring diameter
 16.9 mm
Ring width
 3.0 mm
Finger length
 64 mm
Finger coverage
 57% vs 62%
Saved...
Ring diameter: 16.9 mm
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Actual sizes of 4ct Sapphire Round (9.49×9.49mm, Blue) and 4ct Diamond Round (10.32×10.32mm, White) as they would appear on a ring and finger. Adjust the ring and finger size to get an idea of how these gemstones would look on your finger.

Where to buy?

For certified gemstones, high-end gemstone jewelry, and birthstone jewelry, see Blue Nile

Face-up Size

All things being equal, Sapphire will face-up smaller than Diamond for a given carat weight, because it has higher specific gravity (4 vs. 3.52 - this means it's "heavier" compared to Diamond of the same size). Face-up size also depends heavily on the proportions of the cut.

Face-up area is a measure of the size of the gem when viewed from above (as set in a ring). It tells you how big the gem is at the girdle plane.


4 Ct Sapphire (Round) 4 Ct Diamond (Round)
9.49×9.49 mm vs 10.32×10.32 mm
70.73 mm²   83.65 mm²
Face-up size outline for 4ct Diamond (10.32×10.32mm, round cut)
Face-up size outline for 4ct Sapphire (9.49×9.49mm, round cut)
4ct Sapphire Round (9.49×9.49mm)
4ct Diamond Round (10.32×10.32mm)
Difference: 18% (12.92 mm²)
4ct Diamond (Round, 10.32×10.32mm) has approx. 18% more face-up area than 4ct Sapphire (Round, 9.49×9.49mm).


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