Pearls per strand.

Answer

Pearls on a strand = usable length / (pearl diameter + knot gap), rounded down. Usable length is the strand length minus the clasp. An 18 inch strand is 457.2 mm, so it holds 65 round 7 mm pearls laid tight (457.2 / 7 = 65.3).

Worked example

An 18 inch strand of 7 mm pearls, no knots, no clasp: 18 x 25.4 = 457.2 mm; 457.2 / 7 = 65 pearls with 2.2 mm to spare. Add a 1 mm knot gap and a 25 mm clasp: (457.2 - 25) / 8 = 54 pearls. For length, 60 pearls of 6 mm with no gap make 360 mm, which is 36.0 cm or 14.17 inches.

How it works

Pearls = floor((length - clasp) / (diameter + gap)). Length = pearls x (diameter + gap) + clasp. 1 inch = 25.4 mm. This is plain geometry for round pearls in a straight line. Cultured pearls vary in size and shape (Akoya pearls generally range from 2 to 10 mm), so graduated or baroque strands will not match the count exactly. Pearl dealers also sell by weight in momme, where 1 momme is 3.75 g.

Sources and basis (opened 2026-10-08): Wikipedia, Pearl.

FAQ

How many pearls are in an 18 inch necklace?

About 65 round 7 mm pearls laid tight with no clasp, because 457.2 mm divided by 7 mm is 65.3. Knots and a clasp reduce the count.

How do I work out pearls per inch?

Divide 25.4 mm by the pearl diameter. For 7 mm pearls that is 25.4 / 7 = 3.6 pearls per inch.

Do knots between pearls change the count?

Yes. Each knot adds a small gap. Enter the gap in millimetres and the calculator adds it to each pearl.

How long is a strand of 50 pearls?

It depends on the size. 50 pearls of 8 mm with no gap is 400 mm, about 15.7 inches, before any clasp.

Are pearls always round?

No. This calculator assumes round pearls. Baroque, oval or graduated strands need a physical lay-out.