Diamond Weight Calculator

1) Diamond Shape

Select the shape of your diamond below:

round diamond


oval diamond


heart diamond


trillion diamond


princess diamond


baguette diamond


emerald diamond


radiant diamond


marquise diamond


pear diamond


2) Measure the diamond (table up) across its widest points

3) Measure the diamond (table up) across its narrowest points

4) Measure the depth or height of the diamond

Your Diamond Carat weight is:
Diamond Measurements
1 Carat
1 Carat
2 Carat
2 Carat
3 Carat
3 Carat
4 Carat
4 Carat
5 Carat
5 Carat
10 Carat
10 Carat

Use this calculator on your site

Diamond Weight Faqs

  • How do you calculate the weight of a diamond?

    Find out its weight in grams and divide this by 0.200 (the weight of one carat) to calculate a diamond’s carat weight. 

    You can also roughly calculate a diamond’s weight based on its cut, diameter, and height in millimeters. But remember that a carat is a unit of weight, it’s not a measure of size. Plus, differences in density mean that two different one-carat diamonds can be of different sizes.

    Try Peter Norman’s diamond calculator above if you’d like to get an approximate weight based on millimeters.

  • How heavy is a one-carat diamond?

    0.200 grams is equal to one carat, so a one-carat diamond weighs 0.200 grams. 

    However, diamond weight is generally measured in carats, so a one-carat diamond weighs exactly one carat.

  • How heavy should an engagement ring diamond be?

    There is no set ‘rule.’ Instead, you should select the best possible diamond that’s within your engagement ring budget. 

    If you’d like to visualize a diamond’s size based on its weight, try Peter Norman’s diamond weight calculator above. Simply select the cut, then enter the gem’s widest, narrowest, and depth measurements

  • How much is 7 mm in carats?

    A round-cut diamond with a 7-mm diameter and a 3-mm depth weighs approximately 0.9 carats. We’ve based this on our diamond calculator above, for a more accurate result, select the cut of your diamond.

  • How many mm is a one-carat diamond?

    It depends on several factors including the diamond’s cut, and the measure (in millimeters) of its depth and narrowest point. You can use Peter Norman’s diamond weight calculator above to get an approximate measurement.

    Remember though, that a diamond’s density also plays a part — different gemstones have varied densities, so even if we had three different gems of the exact same cut and carat weight, they could be slightly different sizes in millimeters.

  • What does an 18 carat diamond mean?

    An 18-carat diamond means the gem is both heavy and expensive. Carat is a measurement of diamond weight and, density aside for a moment, this roughly corresponds to its size. 

    If you’d like help imagining how much a diamond weighs in carats, try our diamond weight calculator above.

  • What is a 0.25-carat diamond worth?

    It depends on the market and the diamond’s GIA rating. Because diamonds are a commodity, their price can fluctuate, and because carat isn’t the only measure of a diamond’s quality, its carat weight alone doesn’t dictate its value. 

    At the time of writing (2022), the diamond market was strong with the prices for wholesale mined and polished diamonds rising.

  • Is a 0.25-carat diamond good?

    All diamonds are good! A 0.25-carat diamond is a quarter-carat diamond and it is enough weight to add a lovely sparkle to any engagement ring.

    If you’re looking for something bigger without breaking the bank, consider lab-grown diamonds. Plus, they look absolutely identical to a mined diamond and are chemically the same; even a jeweler can’t tell by sight if a diamond is lab-grown.

  • Is a 1 carat diamond too small for an engagement ring?

    It depends who you’re asking! Plenty of people love their one-carat diamonds, and this weight is a common choice for engagement rings. 

    Remember that weight isn’t the only measure of a diamond’s value. Factors such as clarity and density also affect a diamond’s size.

  • Is a higher carat always better?

    No. Carat is not the only measure of a diamond’s worth. For example, a six-carat diamond with a ‘flawless’ GIA rating will always be worth more than a seven-carat diamond that’s graded ‘included’, which means its inclusions (flaws) are obvious. Cut is also a factor.

    If you’re struggling to understand what factors determine a diamond’s value, take a look at our guide to buying an engagement ring or have a play around with our diamond weight calculator above to see how a diamond’s shape correlates to its weight.

  • X

    Wait! before you go...

    Join our newsletter, and receive our free
    "Complete Guide to buying an engagement ring."