Soft Body Armour Panels: Coverage, Areal Density, Pack & Vest Mass, Fabric per Vest

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 9 inputs are read from the form on every keystroke: Front Panel Area, Back Panel Area, Side Panels, Both, Ballistic Layers, Ballistic Fabric Weight, Waterproof Cover Fabric Weight, Carrier Mass, Cutting Allowance and Fabric on One Roll.
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 Vest Mass together with every supporting figure in one pass — no value is carried over from a previous entry.
4. The supporting outputs — Coverage Area, Areal Density of the Pack, Ballistic Pack Mass, Waterproof Covers, Ballistic Fabric Cut per Vest and Vests from One Roll — 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

The ballistic pack is nearly three-quarters of the vest's weight.

How to use it

1. Work through the input groups in order — Coverage and Pack & Carrier. 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 Vest Mass in the dark results panel — that is the headline figure, expressed in kg.
4. Check the supporting rows underneath (Coverage Area, Areal Density of the Pack, Ballistic Pack Mass, Waterproof Covers, Ballistic Fabric Cut per Vest and Vests from One Roll) 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 Vest Mass 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 — Vest Mass 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 Front Panel Area) shows how much of the gap in Vest Mass 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

• Panel areas, layer count, fabric weights and the carrier are the design's. Areal density is the layers times the fabric weight, the figure armour packs are compared by; the pack mass is that over the coverage. Covers are counted as two faces of each panel. Stitching, labels, trauma pads and plates are not included. Fabric per vest is every layer over the coverage plus the cutting allowance. **The protection level comes only from the certified test of the actual pack; this tool weighs a design and does not say what it stops.**
• Every input is bounded to the range normal practice occupies (Front Panel Area 100 to 20000 cm², Back Panel Area 0 to 20000 cm² and Side Panels, Both 0 to 10000 cm², 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

• NIJ Standard 0101.06 and its successor 0101.07, Ballistic Resistance of Body Armor (US National Institute of Justice).
• National police and defence body armour standards, which certify packs by level against stated threats.

Questions people ask