Diamond Buying Guide

For Round Brilliant Diamonds

As part of this buying guide, we’ll walk you through the steps of figuring out what to buy, how to choose a quality diamond, and picking the perfect diamond that fits your budget/need.

This diamond buying guide for round brilliant diamonds assumes you’ve already done a bit of homework on ‘how to buy a diamond‘ and are fairly well versed with the basic properties of diamonds, namely the 4 C’s:

Let’s get started:

1. Help Me Define My Budget

The first and most important thing to do is to set your budget. Give this one a considerable amount of thought.  Put aside everything you’ve heard about “how much should I spend on a diamond ring” as the majority of it is the jewelry industry’s marketing engine hard at work.  For a little fun and to put things in perspective, think about some common sayings about diamonds buying:

Diamonds are a girl’s best friend
Ask any girl wearing a diamond to tell you 3 things about their diamond. You’ll be hard pressed to find a woman who can name more than two – usually size and color, or size and clarity. Not being able to name a third thing about your best friend makes you not so much of a good friend!

Spend 2x your monthly salary
Look for two similar diamonds from two different women. Can you tell which diamond cost 1 month’s salary versus the one that cost 4 month’s salary? Most likely not. Retailers have conditioned us through marketing into spending more than we should.  Case in point, compare two equivalent diamonds – one sourced from Birks and one sourced from Blue Nile. One cost 3x as much as yet they are both equally beautiful. This is brand marketing at its best.  Don’t be fooled by it.

Buying a diamond is an investment
While it is true that diamonds are a precious commodity and that their market value may increase over time, no one should be purchasing an engagement ring as a way to drive financial growth. Case in point: Ask your investment banker when the last time he/she bought an engagement ring to diversity their portfolio.

Treat budget in the same way you would when buying a car. Set the budget before you start shopping rather than letting a sales person tell you how much to spend.


Average Price for Carat: Which one appeals to you?

The average spend on a 1.0+ carat diamond ring is approximately $4000.  In contrast, the average spend on a 0.5 carat diamond is about $1500.  Decide which of these two seems more in line with your lifestyle and financial position and go from there.

2. How to Identify a Quality Diamond

Diamond Filter

Search Funnel: Proportions > HCA > IdealScope

Given that you are reading this, you’re astute and know the facts – buying a diamond online is considerably cheaper than buying a diamond through a brick and mortar retailer. Overall, buying online will save you about 2/3 the costs. This being said, you still need to know –

Given the thousands of diamonds available online, how to I select the best diamond for my budget??

In order to do this, the following sections of this diamond buying guide will help you identify the right diamond properties to look for and then help you weed out the poor performing diamonds using a number of methods and tools.  In a nutshell, the process consists of 3 steps:

  1. Weeding out poorly proportioned diamonds
  2. Selecting diamonds with excellent light return
  3. Narrowing down the high visual performing diamonds


STEP 2a: Weed out POORLY proportioned diamonds


Advanced Search Function: A feature offered by many online diamond retailers

Limit your search to only well-proportioned diamonds. Many online sites allow you to filter diamonds based on “advanced characteristics” (refer to image above). Use this and start by limiting your search based on the following properties when available (some sites only allow for Depth and Table):

Property Ideal Value
Total Depth between 59 – 61.8%
Table Diameter between 53 – 57.5%
Crown Angle between 34.3 – 34.9 degrees
Pavilion Angle between 40.6 – 40.9 degrees
Girdle Edge thin to medium

To make your searching easier, we’ve provided links to a few of the popular online diamond vendors.  These links open up the respective vendors’ diamond search page with the right properties already set.  Remember to put in your budget and other personal criteria like size and color.

When putting in the 4 C’s, our recommendation is to always start with the strictest criteria your budget allows. The following is an excellent starting point that provides the best purchase for your budget (i.e. maximum beauty with minimum budget)

  • Cut : Ideal
  • Clarity : SI2 – VS2
  • Color : H – J
  • Carat : This is up to you

To get good value, select a range just below the usual thresholds (i.e. 0.45 – 0.49 for a half carat ring, 0.90 to 0.99 for a 1 carat ring).   As you narrow down your choices, if you feel that you’re not getting many good results, then relax your search parameters in the following order:

Order in which to relax your criteria:



STEP 2b: Remove diamonds with noticeable inclusions

Online diamond retailers have made great strides in recent years bridging the gap between viewing a diamond in store and viewing a diamond online. Most online retailers now offer photos and images of the diamonds within their inventory. Those online diamond vendors that carry a mix of real and virtual inventory at minimum share real diamond images of their premium line of diamonds.  Thanks to all this technology, it’s increasing easier to achieve this next step in the diamond buying guide with minimal effort.

Spotting inclusions in this step is the same as what you would do in-store except without all the squinting. Comb through the diamonds that match the well proportion criteria and start to look for those diamonds which appear eye clean. An eye clean diamond for the purpose of this buying guide is any diamond that appears free from noticeable inclusions on first look.

Have a look at the screen above courtesy of James Allen. 4 of the 6 diamonds displayed on the page have easy to spot inclusions. We can rule these diamonds out without the need to view the diamond on its own.

Tips on how to judge an inclusion:

  • Inclusions close to the table (face of the diamond) will appear much more noticeable then an inclusion towards the tip of the diamond
  • Black spots near the girdle (outer edge of the diamond) reduce the value of the diamond but can often be covered with a prong from the ring.  This makes for a good value diamond.
  • Inclusions which are hard to see on your screen will be essentially invisible in real life (online diamond images are enlarged several fold). In addition, most people view a diamond from approximately 2ft / 24″ away.

Additional Online Features to Spot Inclusions
Some leading online diamond vendors offer a 360 degree view of the diamond. This is EXTREMELY helpful in pinpointing other inclusions which might be invisible from a straight on shot of the diamond.


Click to view rotation

Take the following diamond for example, can you notice the inclusion??  Rotate the diamond a few degrees left and right.  Can you spot the inclusion on the table?  It’s at the base of the South-East arrow.  The following image provides a zoomed in view of the inclusion.  Notice how small the inclusion is even at high magnification.  Not all diamonds will be this clean so exercise flexibility when narrowing down your selection.zoom

Start Keeping Track of Good Diamonds
At this point, it helps to start a list of your possible candidate diamonds. My personal favorite way to build this list is Evernote (or Dropbox).  Using your tool of choice, save the diamond inventory number and a few comments about it – this will come in handy later.  If your list of diamonds is getting too long, open the certificate associated to the diamond and use the inclusion map to help weed out some of the poorer performing diamonds.  Note that some diamonds less than 1 carat do not have an inclusion map in the certificate.

Step 2c: Finding diamonds that shine with the Holloway Cut Advisor 

Gauging Light Return
The Holloway Cut Advisor (HCA) is a mathematical prediction tool that takes in the proportion of a diamond and evaluates the amount of light returned based on a computer model. The more light returned, the more desirable the diamond. By entering in the specifics of a diamond into the tool, one can get a rating of that diamonds light performance.  This being said, take note that this step is more involved as you will need to copy-paste diamond specifics for each candidate diamond. The fewer diamonds you need to apply the Holloway Cut Advisor against, the easier your life will be.


HCA Score of 0-2 Represent Great Diamonds
Our goal is to find a diamond with HCA score in the 0-2 range.  One key thing to note in this step is that a lower score does not necessary represent a better diamond (i.e. 0.5 is not better than 1.5). For each of the diamonds on your selection, take note of the score. Also, our recommendation is to keep those diamonds that are slightly above a HCA score of 2.0 as these often times are very good purchases.

Step 2d: Creating Your Final Selection of Diamonds using IdealScope

At this point, you should have narrowed down your selection to no more than rough 10 diamonds after the HCA scoring. One key thing to remember is to not use the HCA for final selection. Because it’s built on a computer model, some aspects of a diamond are not accounted for. Final selection should always be done with an IdealScope or an appraisers help.

Measuring Visual Performance for Final Selection
This step in our diamond buying guide is the easiest as we are looking for a shade of red within a diamond image.  This diamond image with shades or red and black is generated from an IdealScope.  In simple terms, an IdealScope is a simple bright colored reflector with a viewing hole and lens. Online retailers leverage this tool to photograph the diamond under the lighting condition it creates. The results are an image of the diamond that gives an indication of a diamond’s brilliance (i.e. the light return and the light that leaks out of the diamond).

Not all diamonds have IdealScope images shown on the detail page, however this does not mean that it cannot be requested.  Online vendors are usually happy to accommodate the request for your final selection of diamonds.

manuf_leakageBased on the Idealscope image, identify the candidates with strong light performance. Here’s a breakdown of the colors

  • Areas of white and pale pink = light leakage
  • Consistent spread of red / pink = more brilliance
  • Even spread of black and pink = good scintillation

An eight arrow pointed start is a good indicator of excellent symmetry.  Here’s a reference chart on symmetry: http://www.ideal-scope.com/1.using_reference_chart.asp.

3. Making the Final Choice 

By now, your selection should be narrowed down to 2 or 3 choice diamonds. It’s always a good idea to put these diamonds on hold with the vendor.  Most online vendors have gemologists on staff and so it’s always in your best interest to leverage them.  With everything outlined in this diamond buying guide, complementing it a knowledgeable set of eyes that can perform a side by side review and comment on your final selection is always a smart move!

Be sure to “LIKE” this post if you found the information useful!  Our team is always happy to provide free advice via our comments section.

Happy Shopping!



  1. Hey Leila! If you have an active lifestyle or are likely to do activities that bump your ring, a bezel setting is definitely the way to go. Because the bezel wraps the stone completely, it’s less prone to fall off relative to a traditional prong-based setting. The caveat with a bezel is that because it does wrap around, you loose a bit of incoming light and so the stone won’t look as brilliant as when set in a prong setting. Also, because more material is used, the bezel will cost you a bit more.

    As for the stone itself, make sure you start with an ideal cut grade. That’s going to give you a best return for your money. Remember that a small well but diamond can outperform a larger poorly cut diamond. As for color and clarity, stay within the H-J range and Si2 to VS2 range. You should be able to net something stunning. Because you want something to stand out, make sure you focus on the fire within the stone (i.e. the flashes of color). This will really help make the piece stand out against your pale skin. If you need a personalized list put together, just let us know! Cheers!

  2. My husband would like to buy me a diamond for a solitaire necklace. Our budget is between $1300-$1800. I am thinking I would like it bezel-set (do you have pros/ cons regarding this setting). I have pale skin so it will really need to sparkle to be set off against my skin. What color, cut and clarity would you recommend? I am intrigued by buying online.

  3. Loved this post it was extremely educating. My son is going to buy a diamond and we feel very well informed. Thank you

  4. Hi Trena, no it’s not. There’s a balance between the depth of the stone (height) and the width of the stone. If the stone is too shallow or too deep, light will be lost and the diamond will not look nice. Have a look at the illustration on this page to see what I mean. If you need additional help or a custom list of recommended stones, feel free to contact us using the “Ask your diamond question” form at the bottom of the page.

  5. Hi Jessica,

    Personally, I’m for fluorescence in a stone as long as it impact the effect in a positive way. With a Brian Gavin stone, you’re sure to get that. It’s actually called out on a dedicated page on Brian Gavin Blue: http://www.briangavindiamonds.com/diamond/brian-gavins-blue-diamonds-with-fluorescence/.

    One thing to keep in mind is that the diamond industry is heavily marketing based. Our beliefs have been shaped through advertising to automatically think “fluorescence = bad” when in actually that’s generally not that case. With online retailers, you’re starting to see a shift in that marketing that states that fluorescence no longer detracts from the value of the stone. To that point, I’d go off looks rather than perception and would have no issues with buying a BGD Blue stone.

    Lastly, based on the proportions of both stones, both are well proportioned and will have good light return. For the local jeweller, see if they have an idealscope available for you to view. This will help provide you and apples to apples comparison with the BGD stone.

  6. im torn between two diamonds. One is from a local jewelry. It’s a 2.03 carat J VS1 for $16,900. Triple excellent from GIA. Depth is 60.6, table is 59, crown angle is 34, crown height is 14, pavilion angle is 40.6, pavilion depth is 42.5, girdle is slightly thick faceted 4, cutlet is none, no fluorescence. The other is a Brian Gavin 2.08 carat J VS2 listed for $18,900. Depth is 61.3, table is 56.2, crown angle is 34.6, crown height is 15.1, pavilion angle is 40.8, pavilion depth is 43.1, girdle is thin to medium, cutlet is pointed, fluorescence is strong blue. I love the idea of a diamond that glows in UV light but I know they are not as valuable as those with no fluorescence. What are your thoughts? Thanks!

  7. Hi Matthew,

    In terms of rose gold settings, there are many retailers (i.e. James Allen, Brian Gavin) who offer settings in rose gold or will custom make one (link below).

    With regards to the offers you listed, is the carat weight the total carat weight of the ring? Or just the centre stone? This makes a big difference in terms of whether the prices you’ve listed are a good deal or not. If we look at the centre stone alone, a well proportioned high performing 1.0 carat stone will be about $6,000USD (£4,200). This leaves about $750-ish (USD) for the setting. We can obviously tweak that based on type of setting you’re looking for.

    For the certification, I’d definitely recommend sticking with GIA / AGS as those are the most reputable in the industry.

    To help give you a better sense of whether the rings offered to you are good buy or not, can you share their certificates? This will help me look at the proportions of each stone and uncover whether they are strong performers.


  8. Dear Diamond Advisor,

    I’m really struggling to make a decision on where to buy a rose gold diamond halo engagement ring.

    My budget is around £5000.

    I have been in contact with an online retailer (Rare Pink) who have offered me:

    (a) Halo style (1.01ct), Round Brilliant 1.01ct I VVS2 EX EX VG F = £5295.60 (GIA CERT)
    (b) Halo style (1.0ct) Round Brilliant 1.00ct I VS1 EX EX EX F = £5522.89 (GIA CERT)

    I have also been into a reputable jewellers who have offered me:

    (a) Single Stone Halo (1.04 ct), G, SI2 under an AGI certificate = £5800 (discounted from £6900)
    (b) Similar to above (0.95 ct) E, SI2 under an AGI certificate = £5300


  9. I1 is the clarity grade and G is the colour. It’s best to avoid diamonds with Clarity grade that low as inclusions will almost always be visible.

  10. One question. As I was waiting for your expert opinion. I came across these 2, how do these compare to the one’s you picked out?
    354837 and 487819

    I didn’t realize that between 1.2 and 1.04 that the difference is only 0.5 x 4 sides?

  11. Hi,
    I’m looking for a cushion cut with maximum face up value. I have a budget of 6000.00 and would like a great diamond that is eye clean and near colorless. I also like the chunky look and definitely do not like the crushed ice. I like a symmetrical look much like a white diamond. I plan on using this diamond as a solitaire with no other accompanying diamond. What do you recommend? Should I stay with a G color at VS2? I’d like at least a 1.2 carat if possible since my current setting did house a 1.2 carat round diamond. Any help would be appreciated.

    Thank you

  12. Hi Eric, yes, it’s possible for the diamond to have these values (i.e. no need to switch). If you look at the certification, it usually gives you a clear idea of which is depth and which is table. If you have the certificate link, feel free to include it

  13. This is really helpful, thank you! I was wondering about the HCA report. 61% is entered for depth and 59.1% was entered for the table. Are these correct, or should these be switched? Thanks!

  14. Thanks for your comment, Juliet! From a woman’s perspective, if there’s anything you think would make our buying guide better, let us know! Thanks again!

  15. Fantastic post! Haven’t come across anything quite so detailed before! You make a brilliant first point- that not a lot of women know many details about their ring plus you are right, there isn’t a lot of difference between a ring that costs one months salary and two! These are great points to consider for the inexperienced buyer as it is all too easy to make the wrong move!- Juliet

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