How netting mesh size is measured: bar, stretched mesh or opening
A netting mesh can be stated three ways, and the three give three different numbers for the same net. The bar is one side of the mesh, measured from knot centre to knot centre. The stretched mesh spans two bars, so it is twice the bar. The opening is the inside distance between the knots, and it is the smallest of the three. A quote that gives a mesh figure without saying which one it is cannot be compared with another quote.
What are the three ways to measure a mesh?
ISO 1107, the international vocabulary for netting, defines all three. The wording below is ISO's own, from the 2017 edition.
| Measure | ISO 1107:2017 definition | Also called |
|---|---|---|
| Bar (mesh side length) Half the stretched mesh. | "distance between two sequential knots or joints, measured from centre to centre when the yarn between those points is fully extended" (3.3.1) | half mesh; "square measurement" or "bar measure" at US sellers; "mmsq" at some Chinese factories |
| Stretched mesh (mesh length) Two bars: twice the bar. | "distance between the centres of two opposite knots in the same mesh when fully extended" (3.3.2, knotted netting) | full mesh; "stretch mesh"; "mmstr" at some Chinese factories |
| Opening (mesh opening) Smaller than both centre figures. | knotted: "longest distance between two opposite knots in the same mesh when fully extended" (3.3.4); knotless: "inside distance between two opposite joints" (3.3.5) | clear opening, aperture |
Definitions from the ISO 1107:2017 vocabulary, clauses 3.3.1 to 3.3.5, read on the official preview on 2026-10-01. ISO also notes that the bar is "also referred to" as a half mesh. The trade names in the last column are the ones the sellers and factories cited below use.
The international convention, in FAO's table of national measuring systems, is the stretched mesh and the opening; the bar is listed as a system of "some European countries". US sports netting is sold differently again: depending on the seller, the inch figure on a baseball or golf net is called the bar, the "square measurement" or the opening, and sometimes more than one of these for the same product.
Why does one supplier quote 20 mm and another 40 mm for the same net?
Because the stretched mesh is two bars, every net has a small number and a number twice as large, and both are correct. FAO's training manual on buying netting puts it in one line: "A 25 x 25 mm mesh may be designated either as a 25-mm mesh (bar size) or a 50-mm mesh (stretched size)." The same manual gives a depth as "70 bars of 20 mm (or 35 stretched meshes of 40 mm)".
Sellers do the same in their own listings. A US barrier netting maker describes one product as a "3 1/2" stretched mesh (1 3/4" bar measure)", and calls the same 1.75 in an "opening" a line higher. A Chinese netting manufacturer writes the half mesh as "mmsq" and the full mesh as "mmstr", so that "20mmsq is the same meaning of 40mmstr". Another Chinese maker states the rule a buyer should apply: "A nominal number may describe clear opening, knot-centre spacing or another convention, so every quotation should state how it was measured."
The confusion is old enough to have been written down by the fisheries scientists who deal with it daily. The International Council for the Exploration of the Sea notes that the netting industry states the length of mesh while regulators measure the opening, and that "there is frequently confusion" between the two.
Read on 2026-10-01: FAO, management for freshwater fish culture, chapter 8 (buying netting); LFS, #36 nylon barrier netting; Nettingland, mesh size of fishing nets; Wenetting, custom netting guide; ICES Cooperative Research Report 266, mesh size measurement revisited (2004).
How much smaller is the opening than the knot to knot figure?
Smaller, always, and by an amount that nobody publishes as a rule. Three things are documented. FAO's workbook states that a single knot is about three twine diameters high, so knots take real room in every mesh. A fisheries modelling study postulates that, for the same knot centre to knot centre size, a mesh in thicker twine has a smaller inside opening. And ICES records that in knotted netting the gauge can sit on the knot or next to it, which "may lead to a significant difference in measured mesh opening" in heavy netting.
What does not exist is a formula of the kind "opening equals bar minus one twine diameter". We looked for one in the standards, the FAO manuals and the sellers' pages, and found none. So when the margin matters, and it matters most when a ball is only a little larger than the mesh figure, the opening has to be stated by the supplier, not derived by the buyer. The ball diameters published by the governing bodies are in our mesh size chart by sport; read its seller figures as nominal mesh sizes, since most sellers do not say how they measure.
Does "square mesh" describe the size or the way the net is hung?
It is used for three different things, which is why it should never appear alone in a specification:
- A shape. In ISO 1107, a square mesh is a mesh "in which adjacent sides are at right angles".
- An orientation. In EU fisheries law, a square mesh has one set of bars parallel to the length of the net and the other at right angles to it, which is what sports sellers call netting "hung square" as opposed to "hung diamond".
- A measuring convention. A US seller defines "Square Mesh Measurement (same as Bar Size)". Another lists its nets by "square measurement" on its product pages, and says in its FAQ that mesh size is "a measurement of the opening".
"45 mm square mesh" can therefore mean a 45 mm bar, a mesh whose sides meet at right angles, or netting hung on the square, or all three. Write the measure and the hang as two separate fields: "45 mm bar, hung square".
Read on 2026-10-01: Regulation (EU) 2019/1241, article 6, points 34 to 36; Duluth Sport Nets, net information; Gourock, #36 knotted nylon netting and Gourock, custom netting FAQ.
How is mesh measured on knotless netting?
There are no knots, so the reference points change. ISO measures knotless netting between the joints: the mesh length from joint centre to joint centre, and the opening as the "inside distance between two opposite joints". The ECB names the reference point for each construction in its cricket specifications, "knot to knot" for knotted netting and "weld to weld" for knotless, and gives a different figure for each, as the next section shows.
This is not a detail for us: the netting our manufacturing partner has photographed as factory samples is knotless polyester, and knotted vs knotless netting covers what else changes between the two constructions.
What do the cricket specifications actually say?
Cricket is the one sport where a governing body publishes netting mesh in detail, and its documents show the problem rather than solve it. The ECB's TS2, for indoor cricket centres, recommends "48mm white nylon mesh", followed in the same sentence by "(50mm (2") square knot to knot)". TS2 does not say what the 48 mm is measured between. The later TS3, for sports halls with cricket provision, recommends "50 mm knotted or 40 mm knotless white polymer netting mesh", and names the reference points for its roof netting: "50 mm knot (knot to knot) or 40 mm knotless (weld to weld) square mesh". The ECB's 2025 design guide for covered outdoor facilities repeats the same figures for practice lane netting. We found no definition, in any of the three, of whether "knot to knot" runs from the knot centres or from their inside edges.
So even the most precise published specification leaves one reference point open. If you are buying to an ECB figure, quote the document and the construction, and ask the supplier to confirm the reference points. Lane dimensions are on our cricket net dimensions page.
Read on 2026-10-01: ECB TS3, indoor sports halls with cricket provision; ECB covered outdoor cricket facilities design guide, version 1.1, May 2025. TS2 quoted from the copy published by an ECB-accredited contractor.
How do I measure a net I already own?
Measure several meshes at once, never one. FAO's method for the stretched mesh is to pull a panel fully extended, measure between the centres of two knots ten meshes apart, and divide by ten. A US commercial net maker measures three to six meshes and averages them, and notes that a knotted mesh measures slightly larger when taken depthways, perpendicular to the selvedges. The same maker lists three ways to take a stretched measure, centre to centre, inside to outside and inside to inside, and states the rule that matters: the manufacturer and the buyer must use the same one.
For a replacement, write down what you did: "stretched mesh 90 mm, measured knot centre to knot centre over ten meshes". A figure with its method attached cannot be misread at the factory.
Read on 2026-10-01: FAO Fisherman's workbook, materials and accessories; Fitec, frequently asked netting questions.
What should the specification say?
- The figure and the measure. "22 mm bar" or "44 mm stretched", never "22 mm mesh".
- The reference points. Knot centres, or inside edges; for knotless netting, joint centres or the inside opening.
- The opening, when a ball is close to the mesh size. Ask for it to be stated, not derived.
- The hang, as a separate field. Hung square or hung diamond, so that "square" only ever means one thing.
- The twine. Its diameter in millimetres changes the opening at a given knot spacing; see the twine gauge chart.
These belong in the mesh field of the free quote-comparison matrix and RFQ checklist. The mesh and twine combinations our partner documents are in the Spec Finder, and the full range is under netting by the metre.
Frequently asked questions
Is "20 x 20 mm" the size of the hole or the distance between the knots?
It can be either, which is the whole problem. In FAO notation a "25 x 25 mm" mesh is the bar size, one side of the mesh, and the same net is a 50 mm stretched mesh. Some sellers mean the distance between knots, some mean the clear opening, and the figure alone does not say which. Ask the supplier which of the three measures the number is, and from which reference points it was taken.
Is a 2 inch mesh the same as a 50 mm mesh?
Nominally. Two inches is 50.8 mm, and the trade rounds it both ways: a UK seller lists one cricket net as "48mm (2")", and the ECB TS2 specification recommends "48mm white nylon mesh" followed, in the same sentence, by "50mm (2") square knot to knot". Neither document says what the 48 mm is measured between. Treat a converted figure as nominal until the measure and the reference points are stated.
Which measure decides whether a ball gets through?
The opening, because that is the gap the ball meets. A knot centre figure overstates it, since the knots and the twine take up part of every bar, and no published rule gives the difference in millimetres. When a ball diameter is close to the mesh figure, ask for the opening in writing rather than working it out from a knot to knot number.
How do you state mesh on your own family pages?
As the manufacturing partner lists it, side by side in millimetres, with the inch conversion. Which reference points that figure uses is not documented in the listing, so it is one of the points to settle in the written specification before an order, and the request form is the place to ask.
Holding two quotes with different mesh figures?
Send both as they are. The reply within 2 business days says which measure each figure appears to be, what is missing to compare them, and what to ask for in writing before either is accepted.
We reply within 2 business days with questions or a documented quote.