Free insured shipping across Canada · Delivery within 10 business days
JOUWELL
FR

Guide · Diamond shapes

How to choose your diamond shape

Compare millimetres on the hand, not carats. Every shape below is drawn at its real size; move the slider to see it at any weight from 0.5 to 5 carats.

In more than 40 years of choosing diamonds, our gemologist has learned that shape is the first decision, and the one people rush. It decides how big the stone looks, how it sparkles and how it sits on the hand.

So don’t pick a shape from a picture. Use the tools below to see each one at its real size, then read what to watch for before you choose.

Jouwell, Montreal

01 · Every shape at true size

Stock links show
1.00 ct
Drawn at actual size on most computer screens; phones and zoom change it. Hold a ruler to the 10 mm bar to check yours. Sizes are typical ranges and vary with each stone’s depth.

02 · Compare two shapes

Stone A
Size
8.1–8.2 mm
Face-up area
52 mm²
See this size in stock
Stone B
Size
8.6–9.4 × 6.1–6.6 mm
Face-up area
45 mm²
See this size in stock
5 mm

Face up, stone B (Oval, 1.50 ct) covers about 14% less area than stone A (Round, 2.00 ct).

Enlarged so the difference is easy to see. The bar shows 5 mm at this scale.

03 · On the finger

Stone size
7.5–8.2 × 5.3–5.8 mm
Finger width covered
34%

At ring size 6, the finger is about 16.5 mm wide. This stone (Oval, 1.00 ct) covers about 34% of it.

See this shape and size in stock

Ring sizes are Canadian/US. Finger width is taken from the ring’s inside diameter, so treat it as a guide. Drawn at actual size on most computer screens.

04 · Brilliant or step cut

Two ways a diamond plays with light

Every shape on this page belongs to one of two families, and the family matters as much as the outline.

Brilliant cuts

Round, oval, cushion, princess, pear, marquise, radiant, heart

Many small triangular and kite-shaped facets break light into lots of tiny sparkles. They hide small inclusions well and keep their life in any light.

Step cuts

Emerald, square emerald, Asscher

Long, parallel facets like a staircase give broad flashes of light and dark: the “hall of mirrors”. They show the inside of the stone clearly, so clarity matters more.

05 · The 12 shapes

Each shape, and what we look for

Sizes are for 1 carat. The ratio is length divided by width: a matter of taste, not a grade. Colour and clarity are where we’d start looking, not rules.

  • Round

    Brilliant cut

    The look
    Maximum sparkle, timeless
    1 ct size
    6.4–6.5 mm
    Usual ratio
    1.00–1.02
    Watch for
    The only shape with a GIA cut grade. Use it: ask for Excellent.
    Setting tip
    4 or 6 prongs, or a bezel
    Start at
    G–H, SI1–VS2 eye-clean

    Our advice

    If you can’t decide, a round never disappoints. It returns more light than any other shape, and the cut grade on the certificate tells you most of what you need to know.

    Read the round diamond guide See round diamonds in stock

  • Oval

    Brilliant cut

    The look
    Soft, elongated, a modern classic
    1 ct size
    7.5–8.2 × 5.3–5.8 mm
    Usual ratio
    1.30–1.50
    Watch for
    A dark bow tie across the middle; flat ends
    Setting tip
    4 or 6 prongs
    Start at
    G–H, SI1–VS2

    Our advice

    An oval looks bigger than a round of the same weight and flatters the finger. Never buy one from a photo: we check every oval on video for the bow tie, and a light one that moves as the stone turns is fine.

    Read the oval diamond guide See oval diamonds in stock

  • Emerald

    Step cut

    The look
    Calm, architectural, Art Deco
    1 ct size
    6.5–7.0 × 4.5–5.0 mm
    Usual ratio
    1.30–1.60
    Watch for
    Shows inclusions and colour; a washed-out “window” in the centre
    Setting tip
    4 corner prongs, or a bezel
    Start at
    F–G, VS2 or better

    Our advice

    An emerald cut doesn’t twinkle, it flashes, like light across a still pool. Choose it for that look, and spend on clarity rather than carats: its open facets hide nothing.

    Read the emerald-cut diamond guide See emerald diamonds in stock

  • Cushion

    Brilliant cut

    The look
    Romantic, pillow-like
    1 ct size
    5.5–6.1 mm
    Usual ratio
    1.00–1.10
    Watch for
    Faces up small for its weight; shows warm colour
    Setting tip
    4 prongs or double prongs
    Start at
    G–H, SI1–VS2 (F–G if you see warmth)

    Also comes elongated: about 6.4–7.0 × 5.0–5.4 mm at 1 ct, ratio 1.15–1.35.

    Our advice

    Cushions vary more than any other shape, from crisp “crushed ice” to big, old-style flashes. Tell us which look you love and we’ll find it for you; the certificate alone won’t say.

    Read the cushion diamond guideRead the elongated cushion guide See cushion diamonds in stock

  • Princess

    Brilliant cut

    The look
    Crisp, modern square
    1 ct size
    5.3–5.6 mm
    Usual ratio
    1.00–1.05
    Watch for
    Sharp corners can chip
    Setting tip
    Prongs that cover the corners
    Start at
    G–H, SI1–VS2

    Our advice

    A princess gives you a round’s fire in a clean square. It looks smaller per carat, so compare millimetres, and always protect its four corners.

    Read the princess diamond guide See princess diamonds in stock

  • Pear

    Brilliant cut

    The look
    Graceful teardrop
    1 ct size
    7.9–9.1 × 5.2–5.8 mm
    Usual ratio
    1.40–1.75
    Watch for
    Bow tie, uneven shoulders, an exposed point
    Setting tip
    A V-prong at the point
    Start at
    G–H, SI1–VS2, clean near the point

    Our advice

    A good pear is all about symmetry: the two shoulders should match and the curve should be full, not flat. We look for a clean tip too, because that’s where a stone is weakest.

    Read the pear diamond guide See pear diamonds in stock

  • Marquise

    Brilliant cut

    The look
    Dramatic, the longest look
    1 ct size
    9.5–10.5 × 4.7–5.3 mm
    Usual ratio
    1.60–2.20
    Watch for
    Bow tie; two fragile tips
    Setting tip
    V-prongs on both tips
    Start at
    G–H, SI1–VS2, clean tips

    Our advice

    No shape looks bigger per carat: a 1 ct marquise is about 10 mm long. It’s a bold choice, so pick it because you love it, and protect both tips.

    Read the marquise diamond guide See marquise diamonds in stock

  • Radiant

    Brilliant cut

    The look
    Rectangular sparkle, “crushed ice”
    1 ct size
    6.2–7.0 × 4.8–5.5 mm
    Usual ratio
    1.15–1.50
    Watch for
    Deep stones face up small
    Setting tip
    4 corner prongs
    Start at
    G–H, SI1–VS2

    Our advice

    A radiant is the emerald’s outline with a brilliant’s sparkle, and its cut corners make it sturdy. Many are cut deep to keep weight, so we check the millimetres before the carats.

    Read the radiant diamond guide See radiant diamonds in stock

  • Square radiant

    Brilliant cut

    The look
    Square sparkle, “crushed ice”
    1 ct size
    5.5–5.8 mm
    Usual ratio
    1.00–1.05
    Watch for
    Deep stones face up small
    Setting tip
    4 corner prongs
    Start at
    G–H, SI1–VS2

    Our advice

    A square radiant has a princess’s outline without the sharp corners, so it’s the easier square to wear every day. Check the millimetres: a deep one can face up like a much smaller stone.

    See square radiant diamonds in stock

  • Square emerald

    Step cut

    The look
    Clean, square, hall-of-mirrors flashes
    1 ct size
    5.4–5.7 mm
    Usual ratio
    1.00–1.05
    Watch for
    Shows inclusions and colour; corners cut smaller than an Asscher’s
    Setting tip
    4 corner prongs, or a bezel
    Start at
    F–G, VS2 or better

    Our advice

    A square emerald is the Asscher’s quieter cousin: the same steps, a flatter look and smaller corners. Like every step cut, it shows everything inside, so clarity comes first.

    See square emerald diamonds in stock

  • Asscher

    Step cut

    The look
    Square Art Deco “windmill”
    1 ct size
    5.4–5.7 mm
    Usual ratio
    1.00–1.05
    Watch for
    Shows inclusions; can look dark in the centre
    Setting tip
    4 corner prongs, or a bezel
    Start at
    F–G, VS2 or better

    Our advice

    When an Asscher is cut well you see a windmill of squares stepping down to the centre. It’s a quiet, elegant stone; like the emerald, put your budget into clarity.

    Read the Asscher diamond guide See Asscher diamonds in stock

  • Heart

    Brilliant cut

    The look
    Symbolic, romantic
    1 ct size
    6.2–6.7 mm
    Usual ratio
    0.95–1.05
    Watch for
    Hard to read below 0.50 ct; the cleft and two lobes must be even
    Setting tip
    A V-prong at the point
    Start at
    G–H, SI1–VS2

    Our advice

    A heart says it all, but only if it reads as a heart. Go for at least half a carat, and choose one with even lobes and a crisp cleft; we check both on video.

    Read the heart diamond guide See heart diamonds in stock

06 · How to choose

Four questions to narrow it down

  1. What should the stone do?

    For the most sparkle: round, oval, radiant or cushion. For calm flashes of light: emerald, square emerald or Asscher. To look as big as possible: marquise, oval or pear. For romance: cushion, pear or heart.

  2. How active is the wearer?

    Hands that work hard are safest with shapes that have no points: round, oval, cushion or radiant, or any shape in a bezel. Pear, marquise and heart need V-prongs on their points, and a princess needs its corners covered.

  3. Longer-looking finger, or more width?

    Oval, pear, marquise, emerald and elongated cushion draw the eye along the finger and make it look longer. Square shapes like princess, Asscher and cushion add width to a long, slim hand. It’s a styling effect, not a rule.

  4. What matters more: millimetres, or colour and clarity?

    If size on the hand comes first, marquise, oval and pear look biggest for their weight, and princess, Asscher and cushion look smallest. If you want a very clean, white stone, remember that step cuts show inclusions and cushions show warm colour, so budget for higher grades there.

Then shortlist two or three shapes, compare them at your size with the tools above, and look at real stones on video.

07 · Sizes by carat

Shape size table, in millimetres

Typical face-up sizes for each shape. Real stones vary with how deep they are cut, so always check the measurements on the certificate.

Typical face-up length × width in mm, by carat weight. Square shapes show one range.
Shape 0.5 ct1 ct1.5 ct2 ct3 ct4 ct5 ct
Round 5.1–5.26.4–6.57.3–7.48.1–8.29.2–9.410.2–10.310.9–11.1
Oval 6.0–6.5 × 4.2–4.67.5–8.2 × 5.3–5.88.6–9.4 × 6.1–6.69.4–10.3 × 6.7–7.310.8–11.8 × 7.6–8.411.9–13.0 × 8.4–9.212.8–14.0 × 9.1–9.9
Emerald 5.2–5.6 × 3.6–4.06.5–7.0 × 4.5–5.07.4–8.0 × 5.2–5.78.2–8.8 × 5.7–6.39.4–10.1 × 6.5–7.210.3–11.1 × 7.1–7.911.1–12.0 × 7.7–8.5
Cushion 4.4–4.85.5–6.16.3–7.06.9–7.77.9–8.88.7–9.79.4–10.4
Elongated cushion 5.1–5.6 × 4.0–4.36.4–7.0 × 5.0–5.47.3–8.0 × 5.7–6.28.1–8.8 × 6.3–6.89.2–10.1 × 7.2–7.810.2–11.1 × 7.9–8.610.9–12.0 × 8.5–9.2
Princess 4.2–4.45.3–5.66.1–6.46.7–7.17.6–8.18.4–8.99.1–9.6
Pear 6.3–7.2 × 4.1–4.67.9–9.1 × 5.2–5.89.0–10.4 × 6.0–6.610.0–11.5 × 6.6–7.311.4–13.1 × 7.5–8.412.5–14.4 × 8.3–9.213.5–15.6 × 8.9–9.9
Marquise 7.5–8.3 × 3.7–4.29.5–10.5 × 4.7–5.310.9–12.0 × 5.4–6.112.0–13.2 × 5.9–6.713.7–15.1 × 6.8–7.615.1–16.7 × 7.5–8.416.2–18.0 × 8.0–9.1
Radiant 4.9–5.6 × 3.8–4.46.2–7.0 × 4.8–5.57.1–8.0 × 5.5–6.37.8–8.8 × 6.0–6.98.9–10.1 × 6.9–7.99.8–11.1 × 7.6–8.710.6–12.0 × 8.2–9.4
Square radiant 4.4–4.65.5–5.86.3–6.66.9–7.37.9–8.48.7–9.29.4–9.9
Square emerald 4.3–4.55.4–5.76.2–6.56.8–7.27.8–8.28.6–9.09.2–9.7
Asscher 4.3–4.55.4–5.76.2–6.56.8–7.27.8–8.28.6–9.09.2–9.7
Heart 4.9–5.36.2–6.77.1–7.77.8–8.48.9–9.79.8–10.610.6–11.5

08 · Mistakes we see most

Myths that cost people the right stone

“Carat is size.”
Carat is weight. A 1 ct marquise is about 10 × 5 mm; a 1 ct round is about 6.5 mm across. Compare millimetres.
“There’s an ideal ratio.”
Ratios are taste, not grades. GIA gives fancy shapes no overall cut grade, so two ovals at 1.40 can look completely different. Judge the stone, not the number.
“I can choose an oval from photos.”
Not an oval, a pear or a marquise. A light bow tie that moves as the stone turns is normal; a broad, dark one that stays put is what you want to avoid. Only video shows the difference.
“An emerald cut should sparkle like a round.”
Step cuts flash; they don’t twinkle. Choose that look on purpose.
“Round-cut rules work for every shape.”
Emerald and Asscher cuts show inclusions and colour much more. Plan on higher clarity for them.
“Fancy shape means lower quality.”
“Fancy” only describes the outline. A well-cut oval beats a poorly cut round.
“Any setting will do.”
Pear, marquise and heart points are fragile. Protect them with V-prongs or a bezel.
“Lab-grown fancy shapes are always cheaper.”
Not always. Some lab-grown fancy shapes cost more than rounds of the same size. Check the live prices.
“The wedding band can wait.”
Low-set ovals and emeralds, and stones set east–west, often need a curved or contour band. Think about the band early.

09 · Natural or lab-grown?

The shape advice is the same

A shape looks the same whether the diamond formed in the earth or in a laboratory. Everything on this page applies to both.

What differs is the price, and it moves. With natural diamonds, fancy shapes usually cost less than a round of the same quality, because cutting a round loses the most rough. With lab-grown diamonds that rule doesn’t hold: some fancy shapes cost more than rounds.

So choose the shape first, then compare live prices in Canadian dollars. The switch above the shapes sets which stones the “See in stock” links show.

10 · Questions

Diamond shape questions

Which diamond shape looks the biggest?

For the same weight, the marquise looks biggest, followed by the oval and the pear, because their weight is spread over a long outline. A 1 ct marquise is about 10 mm long; a 1 ct round is about 6.5 mm across. Princess, Asscher and cushion look smallest for their weight.

Which shape is best for short fingers?

Elongated shapes such as oval, pear, marquise, emerald and elongated cushion draw the eye along the finger and make it look longer. It is a styling effect, not a rule: choose the shape you love.

Which diamond shape is the most durable?

Shapes without points or sharp corners: round, oval and cushion, and radiant, whose cut corners protect it. Princess, pear, marquise and heart have corners or points that need protective prongs.

What is a bow tie in a diamond?

A dark band across the middle of an oval, pear or marquise, where light leaks through the stone. A light bow tie that moves as the stone turns is normal. A broad, dark one that stays put is what to avoid, and only video shows it.

Is an oval diamond cheaper than a round?

Often, for natural diamonds, because cutting a round wastes more of the rough. For lab-grown diamonds the order changes with size, and some fancy shapes cost more than rounds. Compare live prices at the size you want.

Is shape advice different for natural and lab-grown diamonds?

No. A shape looks the same whatever its origin, so the same advice applies. Only the prices differ.