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A jeweler’s go-to bench guide to measuring gemstones accurately, featuring tools, techniques, and tips to get it right every time.

Every jeweler knows that the right measurements make all the difference. Whether you're building a custom piece, replacing a missing stone, or setting a full layout, how well a stone fits depends entirely on how well it's been measured and prepped. When you're working under pressure — tight timelines, detailed specs, customer expectations — having a clear, reliable process saves time, prevents a redo, and protects your work.

However, measuring isn’t always straightforward. Stone shapes vary, tools wear down, and even experienced jewelers can miss a detail when it comes to inspecting gemstones. That’s why we put together this guide to give you a practical, go-to resource for accurate, consistent measuring. We’ll walk through the tools you need, how to handle different stone shapes, and a few tips that make a big difference at the bench.

What You’ll Need to Get Started

The first step to consistent results is using the right tools and knowing how to care for them. There are a few essentials that belong at every bench, especially for measuring.

Key tools every bench should have include calipers and digital or sliding stone measuring gauges. Calipers, whether digital or dial, are your workhorse for most standard measurements. They’re great for capturing stone length, width, and sometimes depth, depending on your technique.

Shop Measuring Gauges

Stone measuring gauges are available in various types, such as manual and digital, and are great for quick sizing — perfect for standard jobs when speed matters. If you work with CAD-specific jobs or custom orders often, having a digital reference on hand to record and organize measurements is a smart addition to your setup.

Step-by-Step: Measuring Different Stone Shapes

Every piece is unique, and so is each stone shape. Depending on the job or technicalities, you might need to take different approaches. Let’s take a look at common stone shapes and best practices for measuring them.

Round-Shaped Stones

Start with your caliper and measure the diameter across the widest point of the stone. Since round stones should be symmetrical, take at least two measurements in different directions to confirm consistency. This is especially important when preparing stones for setting.

Fancy Shapes

These shapes require three key measurements: length, width, and depth. Use your caliper to measure horizontally and vertically, top points to bottom points, as well as across the widest point. Then, for depth, measure from the table to the culet. Always record every measurement — this ensures a better fit, especially for custom designs or tight-fitting settings.

Oval-Shaped Stones

Measure the length from one edge to the other, and across the width at the widest part.

Marquise-Shaped Stones

Measure the length from the one point to the opposite point, and across the width at the widest part.

Pear-Shaped Stones

Measure across the length from the top rounded side to the opposite pointed edge, and across the width at the widest part.

Heart-Shaped Stones

Measure the length from the top edge of the lobes to the opposite pointed edge, and across the width at the widest part.

Triangle or Trillion-Shaped Stones

Measure from the center of the flat or curved side (base) to the opposite point in all three directions.

Square and Rectangular-Shaped Stones

For square-shaped stones, measure from one flat side to the opposite and at a right angle from one side to the opposite side. For rectangular-shaped stones, such as baguette, emerald, octagon and cushion, measure across the length from one flat side to the other, and across the width from one flat side to the other.

Unique Shapes

With stone shapes such as hearts, tapered baguettes, or shield and kite, you’ll often need to take multiple measurements from irregular angles. Start by identifying top to bottom points, and then the widest point –– measure across a few axes. These stone shapes are often used in custom settings, so precision matters even more when you’ll likely be building around the stone, not fitting it into a standard setting.

Tapered Baguette and Trapezoidal Shapes 

Measure across the length from one flat side to the opposite parallel side, and across both widths from one point to the other.

Hexagon-Shaped Stones

Measure one flat side to the opposite flat side in all three directions.

To determine the actual millimeter size of every stone shape, download this quick stone sizing chart to reference at your bench.

Free Sizing Chart Download

Tips for Consistency and Accuracy

Small misses can lead to big problems later. Here are a few habits that help you stay consistent.

• Align your stone properly: Make sure it's level and steady when using calipers or gauges. Even a slight angle can throw off your results.
• Don’t over-tighten: Applying too much pressure with your tools can potentially damage stones or the tools themselves, giving you false readings.
• Take multiple measurements: This is especially important for fancy shapes or unique cuts. Measuring twice (or more) helps you catch inconsistencies before they become issues.
• Work under good lighting and magnification: Clear visuals make precise placement and reading much easier. Plus, proper organization will keep you on track –– try keeping trays and stone separators on hand.
• Record your measurements: Whether it’s in a notebook or digital file, having a record helps with repeat work or follow-ups for your customers.

These simple steps can save you hours in rework and build more trust with your customers in the long run.

Precision Protects Your Work

Accurate stone measuring isn’t just a technical step — it’s part of your quality control. It ensures your stones fit securely, your designs hold up, and your customers walk away happy. By using the right tools, following a clear process, and double-checking your work, you protect your reputation and your results.