Sewing machine needle sizes

A sewing machine needle carries two numbers, and only one of them is a measurement. The metric number — NM, from the German Nadelstärke Metrisch — is the diameter of the blade in hundredths of a millimetre, so an NM 80 needle is 0.80 mm thick just above the scarf. The American number is a separate scale that has run alongside it since a metric designation was agreed in 1953. This tool converts between them and, more usefully, tells you what the metric number means in millimetres.

How it is worked out

blade diameter (mm) = NM ÷ 100

That division is the definition of the metric size rather than a conversion factor, which is why it holds for any NM number, including ones no manufacturer stocks. The American equivalent is a different matter: it comes from a published list of pairs, and where the sources we checked do not document a pair, this tool says so instead of guessing one.

Source: NM is defined as the blade diameter in hundredths of a millimetre

Questions people ask

What does 80/12 mean on the packet?

Two names for one needle: NM 80 in the metric system and 12 in the American one. The blade is 0.80 mm thick. Packets print both because both are still in use, and the pairing is fixed — you will never find an 80 paired with anything other than a 12.

Is the American number just the metric one rescaled?

Almost, and that is the trap. Subtracting 20 and dividing by five turns 60 into 8, 80 into 12 and 110 into 18 — but the same arithmetic turns 130 into 22, while the documented pair is 130 and 21. The rule breaks at the top of the range, so this tool uses the published pairs rather than the formula.

Which size for which fabric?

Thicker fabric needs a thicker blade: lightweight cottons and linings sit around NM 70–80, quilting cotton and shirting around NM 80–90, denim and canvas at NM 100 and above. Needle type matters as much as size — a ballpoint for knits, a sharp for wovens — and that is a separate choice from the number this page converts.

Why does my needle say 130/705H as well?

That is the needle system, not the size: it describes the shank shape and length that your machine accepts, and 130/705H is the one almost every domestic machine uses. System and size are independent — 130/705H needles come in every size from 60 to 110.

How often should a needle be changed?

Sooner than most people do. A blunt or slightly bent needle skips stitches, snags knits and can score the throat plate, and none of that looks like a needle problem while it is happening. The blade is well under a millimetre thick, which is why it gives up long before it looks worn.

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