Is a 1.5 Carat Diamond Big? Size in mm and On a Hand

Yes. A 1.5 carat diamond is bigger than the classic 1 carat and a little under the 2 carats most of our customers choose. A 1.5 carat round measures 7.4mm across, which covers 44% of an average finger (Australian ring size M, 16.7mm), a little under half.

View 1.5 carat engagement rings

How big it looks depends on the shape and the hand. An oval, pear or marquise runs further along the finger than a round of the same weight, and the same stone covers more of a slim finger than a wide one. Carat is a weight, so the millimetres below are the better guide.

A 1.5 carat round diamond is 7.4mm across. Carat measures weight (1.5 carats is 300 milligrams, or 0.3 grams), and each shape spreads that weight differently. Median sizes at 1.50 to 1.59 carats, measured on 13 November 2026:

Each stone varies a little with its cut. A deep stone faces up smaller than a shallow one of the same weight, so compare the measurements on the grading report as well as the carat weight.

To see the real size, draw a 7.4mm circle on paper, because screens rarely show sizes true. The diamond carat size chart has more carat weights side by side.

On an average finger, a 1.5 carat round covers 44% of the width, a little under half. The average women's ring size in Australia is M to N (US 6 to 7), and the smaller or larger your ring size, the more or less of the finger the same stone covers.

This is the share of the finger a round diamond covers at five ring sizes, using the inside diameter from the ring size chart as the width of the finger:

A 1.5 carat round on a size 5 finger (AU J½) covers 47%. On a US 4 it covers 50%, about what a 2 carat covers on an average finger, and on a US 9 it covers 39%, the share a 1 carat covers on an average finger.

A 1.5 carat oval looks different on the hand again. It is 6.5mm wide, as wide as a 1 carat round, and 9.3mm long, so across the finger it looks like a 1 carat and along the finger it looks bigger. That length is what an oval engagement ring adds at 1.5 carats.

A 1.5 carat round is 0.9mm wider than a 1 carat round (7.4mm against 6.5mm) and has about 30% more face-up area. The weight goes up 50%, but carat is a weight, so the stone looks clearly bigger without looking half as big again.

On an average finger that takes the round from 39% of the width to 44%. In an oval, the same step is from 8.2 × 5.8mm to 9.3 × 6.5mm. More on how big a 1 carat diamond is.

Yes, though it is the smaller of the two steps. From 1.5 to 2 carats the weight goes up a third, the round gets 0.7mm wider (7.4mm to 8.1mm) and its face-up area grows about 20%. The step from 1 to 1.5 carats adds 0.9mm and about 30%, so it shows more on the hand.

On an average finger a 2 carat round covers 49%, against 44% at 1.5 carats. A 2 carat oval measures 10.4 × 7.2mm, against 9.3 × 6.5mm. The 2 carat size guide has every 2 carat measurement.

No, not for everyday wear. A 1.5 carat round covers a little under half of an average finger, so it is easy to notice and comfortable to live with.

On a small hand it reads bigger. On a US 4 finger a 1.5 carat round covers 50% of the width, which is about what a 2 carat covers on an average finger. If you like that look, it suits a small hand well, and if you would prefer something quieter, 1 carat on a US 4 covers 44%, the same share 1.5 carats covers on an average finger. Engagement rings for small hands goes through the proportions.

Yes. It is a clear step up from 1 carat on the hand, and it costs less than 2 carats: complete 2 carat rings start $600 higher than 1.5 carat ones. If you are deciding between 1 and 2 carats, 1.5 gives you the larger share of the visible gain, since the first half carat adds more width than the second.

On 13 November 2026, our complete 1.5 carat lab-grown diamond rings cost $3,650 to $4,450 in 18k gold and $3,700 to $4,600 in platinum, across 14 designs. Each has a 1.50 to 1.59ct E to F colour, VVS1 clarity lab-grown diamond with an IGI report, on a 2mm band, and the price includes the diamond and the setting.

A loose 1.5 carat lab-grown diamond costs less again. Median loose prices by shape on the same day, in Australian dollars:

• Round: $1,643
• Emerald: $1,644
• Pear: $1,667
• Princess: $1,730
• Radiant: $1,750
• Oval: $1,764
• Cushion: $2,159
• Marquise: $2,279

At the median, a loose 1.5 carat round costs about $380 more than a 1 carat round ($1,263) and about $900 less than a 2 carat round ($2,544). Complete 2 carat rings start at $4,250 in 18k gold.

The marquise is the longest shape at 1.5 carats, at 11.9mm, followed by the pear at 10.3mm and the oval at 9.3mm. Long shapes look larger because they cover more of the finger's length.

The oval is the middle ground. It is as wide as a 1 carat round and 9.3mm long, so it adds length without the points of a marquise or pear. The oval buying guide covers what to look for.

The princess is the smallest face-up, at 6.3 × 6.2mm. The emerald (7.9 × 5.5mm), radiant (8.0 × 5.8mm) and cushion (7.1 × 6.4mm) are all a little longer than they are wide, and the round is 7.4mm across.

A 2mm band suits a 1.5 carat diamond. From about 1.5 carats the band needs that width to give the stone a base that matches it, and bands come in 1.8mm, 2mm, 2.5mm and 3mm.

A slimmer band makes the stone look larger, and a wider one gives the ring a bolder look. The band width guide compares the widths.

Yes. A 1.5 carat diamond is 7.4mm across as a round and 9.3mm long as an oval, which covers a little under half of an average finger. It is a visible step up from 1 carat and only 0.7mm narrower than 2 carats.

Compare every design in the 1.5 carat collection, each priced with its diamond and made to order in Melbourne.

Thanks for reading,
Jared and Brie