Best Oval Diamond Ratio: How to Avoid the Bow-Tie Effect

An oval diamond’s ratio is the length divided by the width of the stone. This measurement determines whether the diamond looks wider, more elongated, or unbalanced.

For example:

• A diamond measuring 8.4 mm x 6.0 mm has a ratio of 1.40
• A higher ratio means a longer, slimmer oval
• A lower ratio means a wider, rounder oval

There is no single “perfect” ratio, but there is a preferred range that offers the best balance of appearance and light performance.

The best oval diamond ratio typically falls between:
1.35 – 1.50

This range produces oval diamonds that look well-proportioned, visually larger, and balanced on the hand.

Ratio Breakdown:

• 1.35 – 1.40
  Slightly wider oval appearance. Ideal for buyers who want a fuller look.
• 1.40 – 1.45 (Most popular)
  Balanced shape with strong finger coverage and excellent visual appeal.
• 1.45 – 1.50
  More elongated and slender. Great for those who prefer a dramatic, modern look.

Ratios below 1.35 can appear too round, while ratios above 1.50 may look narrow and reduce sparkle.

For most buyers, 1.40–1.45 offers the best combination of size appearance and symmetry.

The bow-tie effect appears as a dark shadow across the center of an oval diamond, shaped like a bow tie. It occurs when light does not reflect evenly through the stone.

This effect is common in elongated diamond shapes such as oval, pear, and marquise. However, the intensity of the bow-tie varies significantly from diamond to diamond.

A faint bow-tie can be acceptable, but a strong bow-tie can reduce brilliance and make the diamond appear dull.

Not directly.
The bow-tie effect is influenced more by cut quality than ratio alone. However, extremely elongated or poorly proportioned ratios can increase the likelihood of a visible bow-tie.

Key factors that affect the bow-tie effect:

• Cut symmetry
• Pavilion depth
• Crown angles
• Light return efficiency

Two oval diamonds with the same ratio can look completely different depending on how well they are cut.

1. Stay Within the Ideal Ratio Range

Choosing an oval diamond between 1.35 and 1.50 reduces the risk of poor light performance caused by extreme proportions.

2. Focus on Cut Quality, Not Just Carat Weight

Oval diamonds are not graded for cut by GIA, so visual evaluation is critical. Look for diamonds that appear bright across the entire surface without a dark center.

3. Choose the Right Setting

The setting plays a major role in minimizing the bow-tie effect:

• Hidden halo settings add light return from side angles
• Raised settings allow more light to enter the diamond
• Proper prong placement helps distribute light evenly

Many buyers choose oval engagement rings with hidden halo or solitaire settings to enhance brilliance.

4. Review Videos or On-Hand Images

Static photos don’t always reveal bow-tie visibility. Rotating videos or real-life images show how light moves through the stone.

No. Almost all oval diamonds have some degree of bow-tie effect. The goal is to find one where it is minimal and not distracting.

A well-cut oval diamond will:

• Reflect light evenly
• Show strong brilliance
• Have a bow-tie that blends naturally into the sparkle

Certain engagement ring styles help oval diamonds perform better visually:

• Oval Solitaire Engagement Rings – clean design, maximum light exposure
• Oval Hidden Halo Engagement Rings – added brilliance without changing the top view
• Oval Halo Engagement Rings – increase sparkle and size perception

Explore oval engagement rings designed with ideal proportions and balanced light performance.

Oval diamonds already look larger than round diamonds of the same carat weight. Choosing the right ratio enhances this effect further by:

• Increasing finger coverage
• Creating a slimming, elongated appearance
• Maximizing visible surface area

This is why oval engagement rings are often chosen by buyers who want a larger-looking diamond without increasing budget.