Leno Mesh Bag: Cut Length, Bag Mass, Bags per Roll & Packaging per Tonne of Produce

The formula

This is the expression the tool evaluates. Every term is named underneath, with the unit it must be supplied in.

How the result is derived

Step by step, from the values you type to the figure on screen.

1. The 8 inputs are read from the form on every keystroke: Flat Width of the Tube, Finished Bag Length, Top Hem (Drawstring Channel), Bottom Seam Allowance, Drawstring per Bag (0 = None), Fabric Weight (One Layer), Tube Length on a Roll and Produce per Bag.
2. Each value is checked against the accepted range in the input table below. A value outside its range stops the calculation rather than producing a misleading figure — the results blank out and a message appears.
3. The validated values are substituted into the expression above, which resolves Mass of One Bag together with every supporting figure in one pass — no value is carried over from a previous entry.
4. The supporting outputs — Cut Length, Bags from One Roll, Bags per kg of Fabric, Bags per Tonne of Produce, Fabric per Tonne of Produce, Bag Mass as a Share of the Fill and Drawstring per 1,000 Bags — come from the same pass, so they always describe the same case as the headline figure.
5. Results are rounded for display only. The full-precision value is used throughout the chain, so reading a rounded intermediate figure back into the tool by hand can shift the last digit.

What each input means

Where to read each value on the floor, the unit it must be in, and the range the tool accepts.

What the tool returns

The headline figure and every supporting value it is built from.

Worked example

Substituting

A tonne of onions needs under a kilogram of mesh, and forty bags.

How to use it

1. Work through the input groups in order — Bag and Fabric & Produce. The defaults are a realistic case, so you can change one value at a time and watch what moves.
2. There is no calculate button. Every figure recalculates as you type or drag, which is what makes this usable for a what-if sweep rather than a single answer.
3. Read Mass of One Bag in the dark results panel — that is the headline figure, expressed in g.
4. Check the supporting rows underneath (Cut Length, Bags from One Roll, Bags per kg of Fabric, Bags per Tonne of Produce, Fabric per Tonne of Produce, Bag Mass as a Share of the Fill and Drawstring per 1,000 Bags) before acting on the headline — they are where an implausible input usually shows itself first.
5. Reset to defaults returns every field to the reference case, which is the quickest way to check whether a surprising result came from the tool or from an input you had changed earlier.

Where this is used

• Process planning — establishing Mass of One Bag before a trial is booked, so machine time and material in Nonwovens & Technical Textiles are committed against a calculated figure rather than an estimate.
• Costing and quotation — Mass of One Bag is an input to the cost sheet, and quoting from a worked number rather than a remembered one is what keeps a margin intact.
• Troubleshooting — when the floor result drifts from plan, entering the measured values (starting with Flat Width of the Tube) shows how much of the gap in Mass of One Bag each variable explains.
• Teaching and study — the accepted ranges bracket normal Nonwovens & Technical Textiles practice, so moving one variable at a time shows the shape of the relationship rather than a single answer.

Reading the result

Typical bands and what each one is telling you.

Assumptions and limits

• The bag is cut from flat tubular fabric, so each bag is two layers of the flat width over the cut length; the cut length is the finished length plus the top hem and the bottom seam. Fabric weight is per square metre of one layer, from the roll label or a weighed sample. Labels, drawstring mass and sewing thread are not added to the bag mass. Bags per roll count whole cut lengths. **Mesh size and bag strength for the produce are the specification's; this tool only weighs and counts.**
• Every input is bounded to the range normal practice occupies (Flat Width of the Tube 10 to 200 cm, Finished Bag Length 10 to 300 cm and Top Hem (Drawstring Channel) 0 to 20 cm, and so on for the rest). Those bounds are guard rails against typing errors, not a claim that the formula fails one unit outside them.
• The calculation is deterministic: the same inputs always give the same result. It carries no allowance for machine condition, operator skill, ambient conditions or lot-to-lot material variation unless an input above explicitly represents one.
• Nothing is sent anywhere. The maths runs in your browser, so the numbers you type never leave the page.

Standards and further reading

• The buyer's or market's packing specification: bag size, fill mass, mesh and colour for the produce.
• Food contact and packaging rules where the bags are used.

Questions people ask