A necklace is not chosen the way a ring is. A ring has a size, a number, an exact measurement. A necklace has a length, and that length decides everything: where the pendant sits, whether it shows under a collar, whether it tangles with a second chain. It is the detail customers regret most often. Here is how to get the diamond pendant necklace length right, and what actually wears out a lab grown diamond necklace.

What chain length to choose for a diamond pendant necklace

Common lengths run from 38 to 50 centimetres (15 to 20 inches). Here is what each one actually does.

38 to 40 cm (15 to 16 in). The necklace sits at the base of the neck, just above the collarbone. It always shows, even under an open collar. This is the dressiest length, and the one that flatters a delicate pendant.

42 to 45 cm (16.5 to 17.5 in). The pendant falls at the top of the sternum. This is the safe length, the one we recommend for a gift when you do not know the preferences. It works with a V neck, a crew neck and an open shirt.

50 cm (20 in) and longer. The pendant drops onto the chest. More relaxed, easier to layer, but it disappears under most closed tops.

Two things the length charts leave out. Body shape counts: at the same length, a necklace rides higher on a fuller bust and hangs lower on a slim frame. Fabric counts too: on chunky knitwear a short necklace gets lost in the collar, while a long one slides over it.

If you are torn between two lengths for a gift, take the longer one. A jeweller shortens a chain easily; lengthening it is harder.

How to measure your neck in one minute

No jeweller's kit needed.

Take a sewing tape measure, or a piece of string and a ruler. Run it around the base of the neck without pulling, just resting on the skin. Write the number down.

That number is your neck measurement. For a necklace that sits comfortably without clinging, add at least 2 cm (about 1 in). For one that falls below the collarbone, add 5 cm (2 in).

Then check your answer against a necklace you already own and like wearing. Lay it flat, measure it end to end including the clasp, and compare. This is the most reliable check, because it accounts for your body shape with no calculation at all.

What stone size for a lab grown diamond pendant

A pendant is looked at head on, from a metre away, against skin or fabric. That is nothing like a ring, which gets examined up close and from every angle.

Three practical consequences.

First: a stone looks smaller at the neck than on the hand. The neck is a large surface, and it swallows small volumes. A stone that feels generous on a finger turns discreet on a sternum.

Second: shape matters more than weight. A marquise or a pear covers more visible surface than a round brilliant of the same weight, because they are elongated. For the same budget, they show up better.

Third: colour carries further than sparkle. A white diamond returns light and sparkles close up. A blue, green, pink or yellow lab-grown diamond reads as a colour, even at a distance and even on a grey day. If you want the pendant to be noticed, this is the strongest lever.

Our guide to the shapes and cuts of diamonds sets out what each cut does with light.

The chain is the part that breaks first

Here is the thing buying guides leave out, because it does not sell stones: on a necklace, the stone is almost never the problem. The chain and the clasp are.

Diamond is the hardest natural material there is. A chain, on the other hand, is a run of soldered links, and every solder is a weak point. A spring clasp contains a tiny moving part that eventually tires.

What actually breaks chains, in real order of frequency: a garment pulled on too fast over the necklace, a bag strap rubbing the same link every day, long hair tied up over the top, and sleep.

Two precautions are worth every care tip going. Take your necklace off before pulling on a jumper. And do not sleep in it: one night of rubbing against a pillow costs more than several days of wear.

The good news: a broken chain can be repaired. A jeweller resolders a link or replaces a clasp for a fraction of what the piece cost. On a recycled 18 carat gold chain that repair is invisible, and it can be done as many times as needed.

925 silver, vermeil or recycled 18 carat gold around the neck

The neck is an in-between zone. Less punishing than a hand, more than an ear.

925 silver. The entry price. It tarnishes in contact with perspiration, and necks perspire. Expect a regular wipe with a polishing cloth. Nothing serious, but it is real upkeep, not theoretical upkeep.

Vermeil. 925 silver covered with a layer of gold. On a pendant it holds up well, because the stone setting does not rub. On the chain it is more mixed: the links rub against each other with every movement, and the gold layer wears there faster than on the pendant. That is the limit of vermeil on a necklace, and we would rather say so.

Recycled 18 carat gold. The colour is the whole material, not a coating: it never leaves, links included. It is also the only one of the three you can repair indefinitely and hand down. On a necklace meant to be worn every day for years, it is the cheapest choice per year of wear. Our article on the advantages of 18 carat gold explains why this particular alloy became the standard in fine jewellery.

Layering two necklaces without tangling them

Layering has become a reflex, and it often fails for one simple mechanical reason: two chains of similar length twist around each other.

The rule that works: at least 5 cm (2 in) between the two lengths. Any closer and they cross constantly while the pendants knock together.

Two more principles. Only one pendant at a time draws the eye: if both necklaces carry a stone, neither stands out. And keep the same metal family on both, or commit fully to the mix. A half mix looks like a mistake.

Finally, if you layer every day, choose recycled 18 carat gold for the lower chain at least. That is the one rubbing against the other, and it is the one that wears fastest.

What really damages a necklace

Four culprits, in order of importance.

Perfume and hairspray. They land on exactly the patch of neck where the chain rests. Alcohol attacks gold layers and dulls silver. The correct order never changes: perfume, hair, then jewellery.

Perspiration. It is acidic and it is constant on a neck. It is what blackens silver fastest. A wipe with a cloth after a hot day is enough.

Clothes. Pulling a jumper over a necklace means tugging on every link. It is the leading cause of broken chains, well ahead of knocks.

Loose storage. A chain thrown into a pouch with other jewellery comes out knotted, and a tight knot snaps a fine link. Hang your necklaces, or lay them flat in separate compartments.

For cleaning detail and the products to avoid, our jewellery care guide covers each case.

The short version

On a necklace, length is the biggest decision, and it is also the one people make fastest. Measure, add 2 to 5 cm (1 to 2 in), and check against a necklace you already love.

For the stone, remember that a neck swallows small volumes: play on elongated shapes and on colour rather than on weight. And for the metal, know that the chain wears out before the pendant, which argues for solid gold if you wear the piece daily.

If the vocabulary of stones is new to you, start with what a lab grown diamond is. Otherwise browse our necklaces, or tell us about a bespoke project.

FAQ

What is the most common necklace length for women?

42 to 45 cm (16.5 to 17.5 in) suits the large majority of body shapes and necklines: the pendant falls at the top of the sternum. It is the length to pick for a gift when you do not know the preferences. If you are hesitating, take the longer of the two, since a chain is easy to shorten.

How do I measure my neck for a necklace?

Run a sewing tape measure around the base of your neck without pulling. Add 2 cm (about 1 in) for a necklace that rests without clinging, 5 cm (2 in) for one that falls below the collarbone. Then check by laying flat a necklace you already wear and like.

What size diamond looks good on a pendant?

Bigger than you think. The neck is a wide surface that swallows small volumes, unlike a finger. An elongated cut, marquise or pear, covers more visible surface than a round brilliant of the same weight.

Is vermeil a good choice for a necklace chain?

On the pendant, yes, it holds up well because nothing rubs. On the chain it is more mixed: the links rub against each other constantly and the gold layer wears faster there. For a necklace worn every day, recycled 18 carat gold costs less per year of wear.

Can I sleep in my necklace?

Better not. One night of rubbing against a pillow tires the links more than a day of wear, and a necklace can catch or knot during sleep. It is also the situation in which a clasp opens without anyone noticing.

My necklace chain snapped, can it be fixed?

Do not throw it away. A jeweller resolders a link or replaces a clasp for far less than the piece is worth. On a recycled 18 carat gold chain the repair is invisible and can be redone as often as needed.

How do I layer two necklaces without them tangling?

Leave at least 5 cm (2 in) between the two lengths. Any closer and the chains cross constantly. Keep one pendant visible, otherwise neither of them stands out.

Fiona