Size guides › 1.25 carat
Diamond size guide
How big is a 1.25 carat diamond?
A 1.25 carat round diamond is about 6.9 mm across — roughly 39% of the width of an average finger. The same weight in another shape can look up to 24% bigger or smaller.
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1.25 carat in every shape, to scale
Same weight, nine cuts, drawn at one scale on a millimeter grid. The emerald spreads widest; the cushion is the most compact. Tap a shape for its own guide.
| Shape | Size (mm) | Area (mm²) | Looks like a round of |
|---|---|---|---|
| Round | 6.93 mm across | 37.7 | — |
| Oval | 8.53 × 6.09 mm | 40.8 | 1.40 ct |
| Cushion | 6.29 × 5.99 mm | 33.7 | 1.05 ct |
| Pear | 9.09 × 5.86 mm | 38.3 | 1.28 ct |
| Marquise | 10.52 × 5.54 mm | 40.9 | 1.41 ct |
| Emerald | 7.78 × 5.56 mm | 41.9 | 1.46 ct |
| Radiant | 6.89 × 5.74 mm | 38.1 | 1.27 ct |
| Princess | 5.91 × 5.91 mm | 34.9 | 1.11 ct |
| Asscher | 6.12 × 6.12 mm | 35.8 | 1.16 ct |
Why carat isn't size
Carat measures weight. How big a diamond looks depends on how that weight is spread — and depth is free to vary.
All three of these rounds weigh exactly 1.25 ct. Cut shallow, it's 7.10 mm across; cut deep, only 6.78 mm, with the difference hidden underneath where nobody sees it. So shop by millimeters, and check them on your own hand.
How it looks on different hands
The same 6.93 mm stone covers 42% of a slim size 4.5 finger, 39% of an average size 6 and 36% of a size 8. That's why a photo of a ring on someone else's hand can mislead you: the diamond looks bigger on a smaller hand.
Living with 1.25 carat
A step past one carat
A quarter carat over the milestone. It reads as noticeably substantial on most hands while still sitting comfortably in standard settings, and it avoids the round-number weights where prices tend to jump. As a round, it shows the most sparkle for its weight, though not the most size: elongated shapes of the same weight cover more of the finger.
It's about two-fifths the width of a US dime (17.91 mm).
Good to know
Worked out for a 1.25 ct round, not copied from a chart.
On the hand: bold
On an average size 6 finger (17.7 mm wide) it covers about 39% of the width — a bold look that clearly reads as a statement stone. On a slim size 4.5 finger that rises to 42%; on a size 8, it falls to 36%.
What the extra 0.25 ct buys
Going up from 1 ct adds 25% more weight but only 16% more face-up area: 0.50 mm to the width. Weight grows faster than the size you see.
The same size in other shapes
To cover the same area from above you'd need about 1.11 ct in an oval, 1.48 ct in a cushion and 1.40 ct in a princess.
Will it fit your setting?
Most settings sold online are made to fit the diamond you choose, so every common style takes a 1.25 ct round: ask for a 6.9 mm head. Here's which are also sold ready-made in that size. How the fit check works.
- Comes pre-madeSolitaire, halo, three stone, bezel and cathedral — ask for a 6.9 mm head.
- Made to orderEast–west — the ready-made heads we could find are for oval stones, so ask for one made at 6.9 mm.
Ready-made sizes are read from named listings — see setting styles. Already have the ring? Enter its head size in the tool.
See 1.25 carat on your own hand
Take a photo, tell us your ring size, and it's drawn at its real size on your finger — free, and your photo never leaves your phone.
Shop a 1.25 ct round
Blue Nile opens already narrowed to 1.16–1.34 ct — the range of weights a stone this size can be — so the first page of results is this size rather than every round they carry. It also asks for a well-cut round's depth (57–66%) and table (52–62%).
Blue Nile
A large online selection of natural and lab-grown diamonds and settings.
See round diamonds →Blue Nile, lab-grown
Lab-grown rounds, narrowed the same way.
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Nearby weights
Drawn to the same scale. Tap one for its guide.
Questions
How big is a 1.25 carat diamond in mm?
A 1.25 carat round diamond is about 6.93 mm across and covers roughly 37.7 square millimeters from above. Other shapes at 1.25 carat have different dimensions; the emerald looks the biggest.
Which 1.25 carat diamond shape looks biggest?
At 1.25 carat the emerald covers the most area from above and the cushion the least — a difference of about 24% for the same weight.
Why can two 1.25 carat diamonds look different sizes?
Carat is weight, not size. A 1.25 ct round cut shallow can measure about 7.10 mm across, and one cut deep about 6.78 mm — the deep one hides more of its weight underneath.
How much of my finger will a 1.25 carat diamond cover?
A 1.25 carat round covers about 39% of the width of an average size 6 finger. On a smaller finger it covers more and looks bigger.
Is a 1.25 carat round too big for a small hand?
It's bold rather than too big: on a slim size 4.5 finger it covers about 42% of the width. Whether that's the look you want is easiest to judge on a photo of your own hand.