Choosing the right diamond doesn't need to be complicated.

Diamond colour is graded on a scale from D (completely colourless) to Z (visibly yellow or brown).

The grade is determined by placing the diamond upside down under specific lighting conditions, which has very little to do with how a diamond actually looks in a ring.

The simpler way to think about it is that either a diamond is colourless to the naked eye or it doesn't. Approach colour this way and most of the complexity goes away.

We tested across different sizes, shapes, and facet patterns and mapping the results back to the grading scale to come to the recommendation

Our recommendation.

• Natural diamonds: minimum H colour.
• Lab diamonds: minimum F colour.

H lab diamonds will still face up colourless, but diamonds in those grades are uncommon in the market (and if they do they have other defects), so the recommendation reflects what you can actually buy.

Some people prefer warmer diamonds or specific fancy colours (like pinks, blues, yellows, greens). You can filter specifically for these in our lab and natural diamond lists. Some fancy colours like champagne may need to be specifically sourced, for requests like this please contact us.

Clarity grades describe the presence of inclusions. These are small internal voids that form as a diamond grows. The grades run from Flawless (no inclusions visible under 10x magnification) down to I3 (inclusions visible to the naked eye).

Again, you can simplify this and aim for one thing, a diamond that's eye-clean. Eye-clean means no inclusions are visible to the naked eye. Going up a grade from there just removes inclusions that are only visible under magnification.

An eye-clean SI1 looks the same as a VVS2 diamond in a finished setting. The price difference between them can be considerable, especially in natural diamonds.

Our recommendation.

• Natural diamonds: minimum SI1.
• Lab diamonds: minimum VS1.

For natural diamonds an SI1 eye clean diamond offers excellent value, you're not paying a premium for inclusions you can only see under a loupe.

For lab diamonds, like with colour, the majority of good quality lab diamonds available in the market sit at VS1 or higher, and there's very little discount for going lower.

The catch with clarity is that the grade alone doesn't tell you whether a stone is eye-clean. Two SI1 diamonds can be graded the same but look different. One might have an inclusion sitting near the back of the stone where it's not visible, the other might have a visible mark on the face of the stone so you can see it without magnification.

The grade is about the presence, size, and number of inclusions, but not where they are or whether they're visible.

Every diamond on our website has been physically checked for eye-cleanliness, and any stone that isn't eye-clean has been filtered out automatically.

So no matter which diamond you pick from the list, it'll be eye-clean. While we’re confident in our choices, all stones are re-checked post purchase and we’ll email you if we do find any concerns. 

Note when you are browsing, the videos on the diamond lists are heavily magnified, so you'll likely see microscopic inclusions even on higher-grade stones. Since all our stones are eye-clean, those inclusions won't be visible to the naked eye in person.

Carat is a measure of weight, not size. Most of the time carat weight is a good approximation for face-up size, but this isn't always the case.

A diamond cut to deep with more weight in belly means it looks smaller from above. A diamond cut shallower will make a diamond look bigger, but look glassy and lifeless.

If a stone meets our cut thresholds covered below, you don't need to worry about this. The proportions are good and the stone looks its weight.

One thing that isn't intuitive is that shape matters too. At the same carat weight, an oval diamond looks bigger than a round and a marquise looks bigger than an oval. It's because the elongated shapes have more weight on the surface than the belly. It's not a huge amount of difference, but it is something to consider.

Beyond that, carat is a personal choice and the variable with the biggest impact on price.

The best way to get it right is to try sizes on in person, or order a 3D-printed version of the design if you're tossing up between sizes.

As part of the bespoke and customise process, the design is rendered on a hand for you to get a sense of scale, with an option to get a 3D-printed version you can try on.

If there's a design on the website you want to compare carat sizes for, that can also be 3D-printed for a small cost, please contact us to arrange this.

Cut is how well a diamond is proportioned and faceted to return light. A well-cut diamond is bright, even, and looks alive. A poorly-cut one looks glassy or lifeless, regardless of what its colour or clarity grade says.

It's also, unfortunately, the most confusing of the four Cs. Two things worth clarifying first.

First: cut refers to the internal facet pattern of the stone, not its shape. Throughout this guide, that's what cut means.

Second: cut grading was developed for round diamonds only. Fancy shapes like ovals, pears, cushions, and others don't come with an official cut grade from the grading labs. And even for rounds, the terminology isn't consistent. GIA's highest cut grade is Excellent, and IGI's highest is Ideal, with Excellent as their second highest. The same word meaning different things.

Why aren't all diamonds cut to the highest standard? It's a fair question. There are two reasons.

The first, more common in natural diamonds, is rough stone economics.

When a diamond is dug up from the ground, it comes with inclusions and voids throughout it. Cutters map out how to get the most value from each rough stone, and often that means compromising on cut to preserve carat weight, or to avoid an inclusion that would drop the clarity grade. A heavier, higher-clarity stone gets a higher price at wholesale than a beautifully cut one at a lower weight.

The second reason is that diamond cutting isn't automated. The final faceting is done by hand, by a skilled cutter, and as with anything that requires skill, there's a wide range in execution.

Because there's no consistent, independent standard for cut across all shapes, a grading lab certificate alone isn't enough to assess how a stone actually performs.

We've developed our own system to help — Light Return

Working with diamond cutters and researchers, we've developed our own set of angles and proportions for every shape we offer, which allows each stone to be assessed against its own standard.

The result is a grade is something we call Light Return. Every diamond listed on our website comes with both its official lab grade and a Light Return grade.

How that grade is used in the stone recommendations is covered in the next section.

Every diamond on our website has been pre-filtered for the issues below. This section is just here to explain what that filter actually covers.

A grading certificate only covers cut, colour, clarity, and carat. But there’s a separate set of characteristics, all visual, that don't appear on the report and significantly affect how a diamond looks in a finished ring. They're easy to miss online, partly because the diamond videos don't do a good job of showing them and because most people don't know what they're looking for.

The filter applied to every diamond listed here removes stones with any of the following. The list is here for transparency, not because you need to assess it yourself.

Brown, Green, or Milky tones (BGM).

A faint brown, green, or milky cast that makes a stone look dull or off-tone, even when the colour grade says it's colourless. Found in both lab and natural diamonds. Doesn't appear on the certificate and is often hidden in product videos.

Unnatural undertones in lab diamonds.

Really cheap lab diamonds can have undertones — grey, brown, blue, or green — that don't appear on the grading report. Grey is the most common. Product videos often use grey backgrounds, which makes it harder to spot.

CVD strain and striations.

A defect specific to lab diamonds grown using the CVD method. When the growing process is shortened to cut cost, the stone can show internal strain which is visible as faint streaks, blurred patches, or a slightly out-of-focus look. None of this appears in the clarity grade.This type of strain exists in a spectrum so it’s about filtering out the ones which will be visible and affect the look of the diamond. 

Bow-tie, windowing, and extinction.

Cut-related defects that affect both lab and natural diamonds. When a stone is cut poorly, light escapes through the bottom of the diamond rather than bouncing back to the eye, which shows up as dark zones (strong bow-ties), see-through patches (windowing), or dead spots (extinction).

Note that the bow-tie effect can be played up online. Bow-tie sits on a spectrum, and nearly all elongated shapes have some degree of it. We've experimented with cutting diamonds without any bow-tie, but the stones ended up looking flat. You need a little bit of contrast to give a diamond depth. What you want to avoid is a strong bow-tie where there are dead zones.