Carat and shape guide
Diamond Carat Estimate and Shape Guide
Carat is weight; shape is outline; apparent size is what the eye sees. Understanding the difference makes a photo-based estimate much easier to interpret.
Photo-based, AI-assisted
What a CaratScanner report covers
Likely stone indicators, apparent shape, an approximate size and carat range, visible color, clarity and cut observations, and broad USD market-value context.
Carat weight versus visible size
Carat is a unit of mass. It does not specify diameter, length, width, depth, or how large a diamond looks when viewed from above. A shallow stone may spread more of its weight across the face, while a deeper stone can hide more weight below the girdle. Both may weigh the same and present very different outlines.
This is why a photograph should not be used to claim an exact carat weight. CaratScanner reports an approximate range based on the visible outline, proportions, and any useful context in the image. The range should be compared with measurements or a scale before a material decision.
- One metric carat equals 0.2 grams and is divided into 100 points
- Face-up dimensions and depth distribution both affect apparent size
- Jewelry settings can hide the girdle and pavilion used to judge proportions
- Perspective and camera distance can distort apparent length-to-width ratio
How diamond shape changes what you see
Round brilliant stones are described by a circular outline, while oval, pear, marquise, emerald, radiant, cushion, princess, and heart shapes each distribute area and facets differently. Elongated shapes often appear larger in one direction than a round stone of similar weight, but visual spread alone does not establish carat.
The cleanest shape reading comes from a centered, face-up photograph with the full outline visible. Tilt can make a round stone look oval, prongs can hide corners, and strong reflections can erase the boundary between the stone and background.
Shape is not the same as cut quality
Shape names the geometry of the outline. Cut quality concerns proportions, facet relationships, symmetry, polish, and light performance. Some grading laboratories use an overall cut grade for limited categories, while fancy shapes are often discussed through measurements and visual performance rather than one universal grade.
CaratScanner can describe visible cut and symmetry cues from the submitted image. Those cues are useful for comparison, but a single view cannot reveal every facet angle or replace measurements from a laboratory report.
Frequently asked questions
Is carat a measurement of diamond size?
Carat measures weight, not face-up width or visual size. One metric carat equals 0.2 grams. Two diamonds with the same carat weight can look different in size because their shapes, proportions, and depth distribute weight differently.
Can a photo give an exact carat weight?
No. A photo does not directly measure mass and often hides depth. With a clear outline and useful scale context, CaratScanner can provide an approximate size and carat range, but exact weight requires a scale or reliable three-dimensional measurements.
Which diamond shapes can the report recognize?
The analysis can provide guidance for common outlines such as round, oval, princess, cushion, emerald, radiant, pear, marquise, heart, baguette, and other recognizable shapes when the stone is clearly visible.
Are shape and cut the same thing?
No. Shape describes the outline, such as round or oval. Cut describes how well facets and proportions manage light. A stone can have an identifiable shape while its cut quality remains difficult to judge from one photograph.
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