Hong Life CalculatorsUnderstanding the sewing machine needle size chart — concept and principle
This chart matches a sewing machine needle's metric size (NM) with the US, Japanese and Korean number and the fabrics it usually suits. Needle packets print both numbers, for example 80/12, and Korean shops often sell needles as 11호 or 14호, so the chart helps you read any packet and choose a needle for silk, cotton, linen, denim or upholstery.
How it is calculated
The size is a lookup. The metric number NM is the blade diameter in hundredths of a millimetre, so NM 80 means a 0.80 mm blade and NM 100 means 1.00 mm. The US/Japanese/Korean number is an older arbitrary scale that runs alongside it: 60/8, 65/9, 70/10, 75/11, 80/12, 90/14, 100/16, 110/18 and 120/19. Because NM is a physical measurement, it is the more precise of the two.
The principle
The needle has to make a hole big enough for the thread to pass smoothly through the eye and the fabric, but small enough not to damage the cloth. Fine, densely woven fabrics need thin needles to avoid visible holes and puckering; thick or stiff fabrics need thick needles so that the needle does not bend, deflect or break. Thread follows the same logic: heavier thread needs a larger eye, which comes with a larger blade. The needle's point type (universal, ballpoint for knits, sharp for microfibres, jeans for denim) matters as much as size.
Worked example
Default input: metric NM 80.
- Find NM 80 in the chart.
- Blade diameter: 80 ÷ 100 = 0.80 mm.
- Read the matching US/Japan/Korea number: 12.
- Read the typical fabric: medium cotton and poplin.
- Result: NM 80 = size 12, for medium-weight cotton such as poplin.
How to read the result
Small numbers (60/8 to 70/10) are for silk, chiffon, organza and lining. Middle sizes (75/11 to 90/14) cover most shirts, dresses, quilting cotton and linen. Large sizes (100/16 to 120/19) are for denim, canvas, upholstery and many layers. When unsure, test on a scrap: skipped stitches, fraying thread or a thumping sound often mean the needle is too fine; visible holes or pulled threads mean it is too thick.
Common mistakes
- Choosing only by size and ignoring point type; knits usually need a ballpoint or stretch needle.
- Using a needle that is too fine for heavy thread, which causes thread breaks.
- Sewing with a dull or slightly bent needle; many makers suggest replacing it for each new project.
- Putting an industrial needle in a home machine; household machines use the 130/705 H system.
FAQ
Frequently asked questions
What is a 90/14 needle used for?
Medium to medium-heavy woven fabrics such as linen, heavier cotton and light denim.
What metric size is a Korean 11호 needle?
11호 corresponds to NM 75.
Which needle is best for general cotton sewing?
An 80/12 universal needle is the usual starting point for medium-weight cotton.
Sources: SCHMETZ, Household sewing machine needle guide (130/705 H system) · Organ Needles, Household needle size chart