How to Compare Two Diamonds Before Buying

When two diamonds look similar on paper, it can be hard to decide between them. A methodical comparison helps you see which one offers better value and which will look better to you. This guide gives you a step-by-step method.

Start with the same basics

Compare like with like. Make sure both diamonds are the same shape, the same type, either natural or lab-grown, and graded by the same laboratory if possible. Grading standards can differ between laboratories, so a grade from one may not be directly comparable with a grade from another.

Step 1: Compare the cut

Cut has a strong effect on sparkle, so start here. For round brilliant diamonds, look at the overall cut grade, polish and symmetry. For fancy shapes, check the proportions, symmetry and polish, and compare measurements. For elongated shapes such as oval, look at the length-to-width ratio and ask whether the stone shows a dark bow-tie across the centre. Video can show how the diamond sparkles in motion, which a grade cannot.

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Step 2: Compare the colour

Look at the colour grades and think about the metal you plan to use. A slightly lower colour grade may look natural in yellow or rose gold, while a higher grade may be preferable in white metals. A one-grade difference is often hard to see once the stone is set, so consider whether the price difference is worth it.

Step 3: Compare the clarity

Check the clarity grade, then look at the clarity plot and images. Where the inclusions are located matters. An inclusion near the edge or hidden under a prong is less visible than one in the middle. Choose the diamond that is eye-clean to you, not just the one with the higher grade.

Step 4: Compare carat weight and measurements

Look at the weight and the millimetre dimensions. A diamond with a slightly lower weight can look the same size or bigger if it is cut with a wider surface. Compare the diameter or the length and width instead of relying only on carat weight.

Step 5: Read the grading reports

Review both reports side by side. Check the report numbers, the dates, the measurements and any additional notes. Look for details such as fluorescence, treatments or comments about the stone. Make sure each report matches the diamond being offered. Our guide to reading a diamond grading report explains each section.

Step 6: Compare images and video

Ask for high-resolution images and video of each stone in different lighting. Look at how each diamond appears from above, from the side and in motion. If possible, compare them in the same setting and under the same light. Beware of heavily edited or enlarged images that make a stone look better than it does in reality.

Step 7: Compare the price and what is included

Compare the total price and what it covers. Check whether the price includes the setting, the report, delivery, insurance and taxes. Work out the price per carat for each stone but do not rely on it alone, since quality differences also affect value.

Step 8: Compare the policies

Look at each seller's returns, warranty, resizing and after-sales services. A slightly higher price with a better return policy can be a safer choice. Our article on comparing jewellery warranty and return policies explains what to check.

Use a simple scorecard

Create a table with the following rows and score each diamond.

• Cut quality and appearance
• Colour in your chosen metal
• Clarity and eye-cleanliness
• Size and measurements
• Report and laboratory
• Total price and inclusions
• Seller policies

Weigh the factors that matter most to you, usually cut first. Write down your reasons so you can see the trade-offs clearly.

Common mistakes

• Choosing only by the highest grades without seeing the stone.
• Ignoring the cut quality.
• Comparing reports from different laboratories as if they were the same.
• Overlooking differences in what the price includes.
• Skipping the return policy.

What if they are very close?

If two diamonds are nearly identical in quality and price, go with the one you prefer visually, the one with the clearer report or the seller you trust more. A small difference in appearance that you notice will matter more than a small difference in grade you cannot see.

Make your choice

Once you have compared the details, you can decide with confidence. To look at options with clear specifications, browse our diamond jewellery.