Moe Diamond Weight Calculator | Professional Gemology Tool
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Length-to-Width Ratio
1.00
Depth Percentage
61.5%
Formula Coefficient
0.0061
Formula: Length × Width × Depth × 0.0061 (Round Coefficient) × Girdle Factor
Dimension Analysis
| Metric |
Value |
Ideal Range (Approx) |
| L/W Ratio |
1.00 |
1.00 – 1.01 |
| Total Depth |
4.00 mm |
N/A |
| Est. Weight |
1.03 ct |
N/A |
Weight Sensitivity (Depth Variation)
Comparison of estimated weight if depth varies by ±5%.
What is a Moe Diamond Weight Calculator?
A moe diamond weight calculator is an essential tool used by gemologists, jewelers, and appraisers to estimate the carat weight of a diamond that is already mounted in a setting. Unlike loose diamonds, which can be placed directly on a scale, mounted stones cannot be weighed without removing them from the jewelry, which risks damaging the setting or the stone.
The term "Moe" often refers to the Moe Gauge, a traditional caliper tool used to measure the dimensions of a diamond. By inputting these precise measurements—length, width, and depth—into a mathematical formula specific to the diamond's shape, we can derive a highly accurate estimate of its weight. This calculation is critical for insurance appraisals, estate valuations, and verifying the specifications of purchased jewelry.
While modern digital calipers have largely replaced the original mechanical Moe Gauge, the underlying principle remains the standard for the industry: using volume and specific gravity to calculate mass.
Moe Diamond Weight Calculator Formula
The calculation relies on the geometric volume of the diamond multiplied by the specific gravity of diamond (approximately 3.52) and a shape-specific adjustment factor. The general formula used in this moe diamond weight calculator is:
Carat Weight = Length × Width × Depth × Coefficient × Girdle Adjustment
Here is a breakdown of the variables used:
| Variable |
Meaning |
Unit |
Typical Range |
| Length |
Longest dimension (or diameter) |
Millimeters (mm) |
3.0 – 15.0+ |
| Width |
Shortest dimension |
Millimeters (mm) |
3.0 – 15.0+ |
| Depth |
Total height (Table to Culet) |
Millimeters (mm) |
2.0 – 10.0+ |
| Coefficient |
Shape-specific density factor |
Constant |
0.0057 – 0.0106 |
Shape Coefficients
Different shapes have different volume distributions. The calculator uses these standard industry coefficients:
- Round Brilliant: 0.0061
- Oval: 0.0062
- Princess: 0.0083
- Emerald: 0.0092 (varies by ratio)
- Marquise: 0.0058
- Pear: 0.0060
Practical Examples
Example 1: The Classic Round Brilliant
Imagine you are appraising a solitaire engagement ring. You cannot remove the stone. Using your calipers (or Moe gauge), you measure:
- Diameter (Length/Width): 6.50 mm
- Depth: 3.95 mm
- Shape: Round
- Girdle: Medium (No adjustment)
Calculation: 6.50 × 6.50 × 3.95 × 0.0061 = 1.018 carats.
Financial Interpretation: A 1.00ct diamond commands a significantly higher price per carat than a 0.90ct diamond. Accurate measurement here confirms the stone hits the critical 1-carat mark.
Example 2: The Deep Oval
You encounter an Oval cut diamond with a thick girdle.
- Length: 8.00 mm
- Width: 6.00 mm
- Depth: 4.00 mm
- Girdle: Thick (+3.5% adjustment)
Base Calculation: 8.00 × 6.00 × 4.00 × 0.0062 = 1.19 carats.
Adjustment: 1.19 × 1.035 (Girdle factor) = 1.23 carats.
Insight: Without accounting for the thick girdle, you would underestimate the weight by nearly 0.04 carats.
How to Use This Moe Diamond Weight Calculator
- Select the Shape: Choose the cut of the diamond from the dropdown menu. This sets the mathematical coefficient.
- Measure Dimensions: Use a precision millimeter gauge or Moe gauge.
- For Round stones, enter the average diameter in both Length and Width fields.
- For Fancy shapes, measure length (tip to tip) and width (side to side).
- Measure Depth: Measure the vertical distance from the top table to the bottom point (culet). If the stone is mounted in a bezel setting where depth cannot be measured, you may need to estimate based on table reflection or profile view.
- Adjust for Girdle: Inspect the girdle (the edge of the diamond). If it appears thick, select the appropriate adjustment to increase the weight estimate.
- Analyze Results: Review the estimated carat weight and the L/W ratio to assess the cut quality.
Key Factors That Affect Results
When using a moe diamond weight calculator, several variables influence the final estimation:
- Measurement Precision: A deviation of just 0.1mm can significantly alter the calculated weight. Always measure multiple times and take an average.
- Girdle Thickness: The girdle adds weight but not visual size (spread). Thick girdles "hide" weight, making a diamond weigh more than it looks.
- Cut Proportions (Bulge): Some fancy cuts like Pears or Marquises may have "bulged" pavilions (bottoms) that add weight not captured by simple L x W x D formulas.
- Culet Size: A large open culet reduces the total volume slightly, though usually negligible for standard estimations.
- Setting Obstructions: Prongs and bezels can prevent accurate measurement. In these cases, the calculated weight is a "best estimate" rather than a guarantee.
- Shape Variations: Not all Emerald cuts have the same corner ratios, and not all Cushions have the same curvature. The standard coefficients are averages.
Frequently Asked Questions (FAQ)
How accurate is this diamond weight calculator?
It is generally accurate within 5-10%. However, variations in cut style (e.g., thick girdles, high crowns) can cause deviations. It should be used as an estimation tool, not a replacement for weighing a loose stone.
Can I use this for gemstones like Sapphires or Rubies?
No. This calculator uses the specific gravity of Diamond (3.52). Colored gems have different densities (e.g., Sapphire is ~4.00), so the result would be incorrect. You need a dedicated gemstone weight calculator.
What is the "Moe" in Moe Diamond Weight Calculator?
Charles Moe invented a specific caliper gauge in the early 20th century designed to measure mounted diamonds and estimate their weight. The term has become synonymous with the method of estimating weight via measurement.
Why does the calculator ask for Girdle Thickness?
The girdle is the widest part of the diamond. If it is thick, it adds dead weight that increases the carat count without increasing the face-up size. Ignoring this leads to underestimation.
What is a good Length-to-Width ratio?
For Round diamonds, 1.00 is perfect. For Ovals, 1.30-1.50 is preferred. For Emerald cuts, 1.30-1.60 is classic. The calculator displays this ratio to help you judge the aesthetic appeal.
Does this calculator work for Old European Cuts?
Old European Cuts often have deeper proportions and smaller tables. While the formula works, you may need to adjust slightly upward or accept a wider margin of error due to their unique geometry.
How do I measure depth if the diamond is set low?
If you cannot use calipers, you can estimate depth percentage based on the visual profile or by measuring the crown and pavilion angles, though this requires advanced gemological training.
Is a calculated weight accepted for insurance?
Yes, appraisals for mounted jewelry typically state "estimated weight" based on calculations like this. Insurers accept this standard practice for items that cannot be unmounted.
Related Tools and Resources
// Initialize variables
var shapeSelect = document.getElementById('diamondShape');
var lengthInput = document.getElementById('length');
var widthInput = document.getElementById('width');
var depthInput = document.getElementById('depth');
var girdleSelect = document.getElementById('girdle');
var caratResult = document.getElementById('caratResult');
var lwRatioDisplay = document.getElementById('lwRatio');
var depthPercentDisplay = document.getElementById('depthPercent');
var coeffDisplay = document.getElementById('coeffUsed');
var formulaText = document.getElementById('formulaText');
var tblLw = document.getElementById('tblLw');
var tblIdealLw = document.getElementById('tblIdealLw');
var tblDepth = document.getElementById('tblDepth');
var tblWeight = document.getElementById('tblWeight');
var canvas = document.getElementById('weightChart');
var ctx = canvas.getContext('2d');
// Shape Coefficients
var coefficients = {
'round': 0.0061,
'oval': 0.0062,
'princess': 0.0083,
'marquise': 0.0058,
'pear': 0.0060,
'heart': 0.0059,
'cushion': 0.0065, // Average for cushion
'emerald': 0.0092 // Base, adjusts dynamically
};
// Ideal Ratios for display
var idealRatios = {
'round': '1.00 – 1.01',
'oval': '1.30 – 1.50′,
'emerald': '1.30 – 1.60',
'princess': '1.00 – 1.05',
'marquise': '1.75 – 2.25',
'pear': '1.50 – 1.75',
'heart': '0.90 – 1.10',
'cushion': '1.00 – 1.10'
};
function validateInputs() {
var isValid = true;
var inputs = [lengthInput, widthInput, depthInput];
var errors = ['lengthError', 'widthError', 'depthError'];
for (var i = 0; i < inputs.length; i++) {
var val = parseFloat(inputs[i].value);
var err = document.getElementById(errors[i]);
if (isNaN(val) || val < 0) {
err.style.display = 'block';
isValid = false;
} else {
err.style.display = 'none';
}
}
return isValid;
}
function getEmeraldCoefficient(ratio) {
if (ratio < 1.5) return 0.0092;
if (ratio 0) ? (calcLen / calcWid) : 0;
// Determine Coefficient
var coeff = coefficients[shape];
if (shape === 'emerald') {
coeff = getEmeraldCoefficient(ratio);
}
// Core Formula: L * W * D * Coeff
var baseWeight = calcLen * calcWid * dep * coeff;
// Apply Girdle Adjustment
var finalWeight = baseWeight * (1 + girdleAdj);
// Update UI
caratResult.innerText = finalWeight.toFixed(2);
lwRatioDisplay.innerText = ratio.toFixed(2);
// Depth % calculation (Depth / Width) * 100 usually, or Depth / Diameter
var depthPct = (calcWid > 0) ? (dep / calcWid) * 100 : 0;
depthPercentDisplay.innerText = depthPct.toFixed(1) + '%';
coeffDisplay.innerText = coeff.toFixed(4);
// Update Formula Text
var shapeName = shape.charAt(0).toUpperCase() + shape.slice(1);
formulaText.innerText = "Formula: " + calcLen.toFixed(2) + " × " + calcWid.toFixed(2) + " × " + dep.toFixed(2) + " × " + coeff.toFixed(4) + " (" + shapeName + ") × " + (1 + girdleAdj).toFixed(3) + " (Girdle)";
// Update Table
tblLw.innerText = ratio.toFixed(2);
tblIdealLw.innerText = idealRatios[shape];
tblDepth.innerText = dep.toFixed(2) + " mm";
tblWeight.innerText = finalWeight.toFixed(2) + " ct";
drawChart(calcLen, calcWid, dep, coeff, girdleAdj);
}
function drawChart(len, wid, dep, coeff, girdleAdj) {
// Data points: -5% depth, Current, +5% depth
var depths = [dep * 0.95, dep, dep * 1.05];
var weights = [];
for (var i = 0; i < depths.length; i++) {
var w = len * wid * depths[i] * coeff * (1 + girdleAdj);
weights.push(w);
}
// Clear canvas
ctx.clearRect(0, 0, canvas.width, canvas.height);
// Set dimensions
var padding = 40;
var chartWidth = canvas.width – (padding * 2);
var chartHeight = canvas.height – (padding * 2);
// Find max value for scaling
var maxVal = Math.max.apply(null, weights) * 1.1;
// Draw Bars
var barWidth = 60;
var spacing = (chartWidth – (barWidth * 3)) / 2;
var startX = padding;
var labels = ["-5% Depth", "Current", "+5% Depth"];
var colors = ["#6c757d", "#28a745", "#004a99"];
for (var i = 0; i < weights.length; i++) {
var val = weights[i];
var barHeight = (val / maxVal) * chartHeight;
var x = startX + (i * (barWidth + spacing));
var y = canvas.height – padding – barHeight;
// Draw Bar
ctx.fillStyle = colors[i];
ctx.fillRect(x, y, barWidth, barHeight);
// Draw Value Text
ctx.fillStyle = "#333";
ctx.font = "bold 14px Arial";
ctx.textAlign = "center";
ctx.fillText(val.toFixed(2) + " ct", x + (barWidth/2), y – 10);
// Draw Label
ctx.fillStyle = "#666";
ctx.font = "12px Arial";
ctx.fillText(labels[i], x + (barWidth/2), canvas.height – 10);
}
}
function resetCalculator() {
shapeSelect.value = "round";
lengthInput.value = "6.50";
widthInput.value = "6.50";
depthInput.value = "4.00";
girdleSelect.value = "0";
calculateWeight();
}
function copyResults() {
var text = "Moe Diamond Weight Estimate:\n";
text += "Shape: " + shapeSelect.options[shapeSelect.selectedIndex].text + "\n";
text += "Dimensions: " + lengthInput.value + " x " + widthInput.value + " x " + depthInput.value + " mm\n";
text += "Estimated Weight: " + caratResult.innerText + " ct\n";
text += "L/W Ratio: " + lwRatioDisplay.innerText + "\n";
var tempInput = document.createElement("textarea");
tempInput.value = text;
document.body.appendChild(tempInput);
tempInput.select();
document.execCommand("copy");
document.body.removeChild(tempInput);
var btn = document.querySelector('.btn-copy');
var originalText = btn.innerText;
btn.innerText = "Copied!";
setTimeout(function(){ btn.innerText = originalText; }, 2000);
}
// Handle canvas resolution for high DPI
function setupCanvas() {
var dpr = window.devicePixelRatio || 1;
var rect = canvas.getBoundingClientRect();
canvas.width = rect.width * dpr;
canvas.height = rect.height * dpr;
ctx.scale(dpr, dpr);
canvas.style.width = rect.width + 'px';
canvas.style.height = rect.height + 'px';
}
window.onload = function() {
setupCanvas();
calculateWeight();
};
window.onresize = function() {
setupCanvas();
calculateWeight();
};