PreciousMetalCalc.comGold · Silver · Diamond
Carat Weight from Measurements
Diamond Weight Calculator
Calculate the estimated carat weight of a diamond from its physical measurements. Works for round, oval, princess, cushion and more.
GIA-aligned estimates
4C grading system
Natural & lab grown
Free · No signup
These are market range estimates based on simplified 4C grade inputs. Actual values vary significantly. Always get a GIA-certified appraisal for insurance or major selling decisions.
e.g. 0.5, 1.0, 1.5, 2.0
Estimated Value
$0
Market midpoint
Low Estimate
$0
Conservative
High Estimate
$0
Optimistic
How Each Grade Affects Value
Cut: Very Good
Brilliance and light performance
Standard
Color: G
Near colorless — difficult to detect
Standard
Clarity: VS1
Inclusions not visible to naked eye
Standard
Natural vs Lab Grown at This Grade
Natural Diamond
$0
Mined diamond
Lab Grown Diamond
$0
~70% lower price, same physical properties
Measure across widest point
Measure shorter axis
Measure girdle to culet
From grading report if available
0.00
estimated carats
Based on shape formula. Within 5-10% of actual weight for well-proportioned stones.
Original purchase or appraisal price
Estimated Resale
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Secondary market
% of Purchase Price
0%
Typical retention
Buyer Offer Range
$0
Dealer / consignment
Where to Sell a Diamond
Online Diamond Buyer
Abe Mor, WP Diamonds, Worthy.com
$0
Local Jeweller
Trade-in or cash offer
$0
Auction (Sotheby's / Christie's)
Best for 2ct+ exceptional stones
$0
Consignment Sale
Worthy, I Do Now I Don't
$0
Diamond Weight Calculator — Key Information
Why Measure?Useful when a diamond cannot be removed from its setting and placed on a scale. Estimates within 5-10% for well-cut stones.
Round FormulaRound carat = diameter x diameter x depth x 0.0061. Example: 6.5mm diameter, 4.0mm depth = approx 1.03 carats.
Shape FactorsEach shape uses a different constant: round=0.0061, oval=0.0062, princess=0.0083, emerald=0.0092.
Depth PercentageFor round diamonds: ideal depth is 59-62.5%. A shallow or deep cut affects both weight and light performance.
Accuracy NoteEstimates assume typical proportions. Very shallow or very deep diamonds will show larger differences from actual weight.
Mm Size Guide1ct round = ~6.5mm diameter. 0.5ct round = ~5.1mm. 0.25ct round = ~4.1mm. Oval 1ct = ~8x6mm approx.