September 17, 2026

Aluminium Foil Thickness Tolerance: What Two Microns Cost You

Thickness tolerance is usually the last line on a specification sheet and the first thing that decides your yield. Here is why it matters more than the nominal gauge.

Most foil enquiries specify a nominal thickness and treat tolerance as a detail. In practice the tolerance band is what determines whether your line runs profitably, because it decides how much material you actually receive and how consistently the process behaves.

Why is nominal thickness not enough?

A nominal figure marks the centre of a band, not the metal that arrives on your dock. The band around it decides what you really buy.

If you order 0.009 mm and the mill ships anywhere from 0.0082 to 0.0098 mm, you are buying a variable. Two consequences follow: the mass you receive per roll drifts with the band, and the process has to absorb that drift.

Dive deeper

A nominal thickness is a design intent. The band around it is the commercial reality, and it is the band that your converters, your laminators and your packing lines meet when the pallet is opened.

Consider the two ends of the band. A coil that leaves the mill at the light end carries less metal per square metre, so a fixed number of running metres gives you less material to sell. A coil at the heavy end carries more, which is generous only until you remember that you paid for the extra. Neither outcome is a defect, yet both move your cost per finished unit.

There is a second effect that is easy to miss. Thickness and the mechanical behaviour of the foil travel together, so a web that sits at different points of the band from one shipment to the next tends to behave slightly differently in tension, in forming and in sealing.

That is why we treat tolerance as a specification line in its own right instead of a footnote to the nominal gauge: written down, agreed with the supplier and measured the same way by both sides. Buyers who compare quotations on nominal thickness alone are comparing the one number that nobody disputes. Our guide to how to choose aluminium foil thickness sets out the trade-offs in plain terms.

What does a workable specification look like?

A workable specification states a nominal thickness and the band around it, then says how the band is measured. Nothing more is needed, but nothing less will do.

The right choice depends on your process, not on buying the tightest band available. Tight tolerance costs more to produce and is wasted if your line cannot hold that precision anyway.

Dive deeper

A workable specification is short, but every line earns its place. It normally carries the alloy, the temper, the nominal thickness, the width and the core, and then the tolerance that applies to thickness together with the way that tolerance is verified.

Two habits separate a specification that works from one that causes arguments. The first is writing the band as an agreed figure rather than copying a market phrase such as commercial or tight. Those two words mean different things to different suppliers, and a purchase order that repeats them without a figure leaves everyone guessing. The second is agreeing where the measurement is taken: at the coil head, at the tail, at mid-width, or across the full web.

It also helps to say what the foil has to do, not only how thick it is. Lines that lacquer, laminate, print or deep draw are sensitive to different parts of the band, and a supplier who understands the end use can often suggest a band that is easier to hold and no worse in service. The tightest band on the market is rarely the cheapest band to run.

Finally, treat the specification as a living document. Processes drift, dies wear and end customers change their packs, so a band that was comfortable last year may need revisiting this year. An annual review costs nothing and prevents the slow accumulation of rejects.

How is tolerance controlled and proven?

Control happens on the mill; proof happens on the sample bench.

Thickness is held by roll gap and tension control during rolling, then confirmed by continuous gauging and by destructive testing on samples from each coil. Good practice is a thickness profile across the strip width, not a single point reading, because edge-to-edge variation is what causes wrinkles in wide webs.

Dive deeper

Control begins at the mill stand. Roll gap, roll speed, tension between stands and the thermal history of the strip all influence how much metal passes per revolution, and a small change in any of them shows up in the thickness of the finished coil. Mills therefore run continuous gauges that watch the web as it moves and feed corrections back to the stand.

Proving the result is a separate discipline. Continuous gauging tells you what the web was doing while it ran, but it does not by itself tell you what the coil will be when it is unwrapped weeks later. That is why samples are taken and measured, coil by coil, and why the reported result is normally a profile rather than a single figure. A profile shows the crown of the strip, the way thickness falls away towards each edge, and any repeating pattern left by the rolls.

For a buyer, the practical question is what the supplier does with that information. Wording varies across the trade, so the way a band is measured is worth agreeing in writing. General background on the material is collected at the aluminium foil entry on Wikipedia. Ask for the profile itself, and not only a headline figure.

What to ask your supplier?

Ask four things: how the band is set, how it is measured, how it is reported, and what happens when a coil sits at the edge of it.

We supply aluminium foil roll and foil for packaging to commercial or tight tolerances depending on your process, with test certificates per batch. If you tell us your line speed and web width, we can recommend the band that suits it.

Dive deeper

The conversation is easier when both sides use the same words. Ask which alloys and tempers the mill normally rolls for your end use; 1050, 1060, 1100, 1235, 8011, 8021 and 8079 all appear in packaging work, and some are easier to hold to a tight band than others. Ask what range of thickness the mill rolls, and whether your gauge sits comfortably inside it or near the limit.

Then ask how the band will be verified and reported: by continuous gauging, by sample testing, or by both, and in what form the result comes back to you. Ask about width and core as well, because a wider web on a 152 mm core behaves differently on a slitting line from a narrow web on a 76 mm core. Widths from 100 mm to 1500 mm cover most converting lines, and cores are normally 76 mm or 152 mm.

Practical terms are worth settling early: how many tonnes of one size make a sensible order, which loading port suits your route, and whether trial coils are wanted before a full run. We quote packaging foil and plain rolls on the same terms, and we are happy to talk through the band before you commit to a size.

How is thickness tolerance quoted differently across gauges?

Gauges are not equal when it comes to holding a band.

Tolerance is therefore agreed gauge by gauge rather than inherited from a single rule, and a band written as a share of nominal behaves differently in use from one written as a fixed amount.

Dive deeper

The physical work of rolling becomes harder as the foil gets thinner. The roll gap becomes a smaller and smaller share of the strip thickness, tension matters more, and the effect of any eccentricity in the rolls grows. That is why the same mill may describe the band for heavy foil and for very light foil in quite different ways.

Relative and absolute bands also behave differently in service. A band expressed as a share of nominal gets narrower in absolute terms as the gauge falls, while a band expressed as a fixed amount stays the same. Two quotations can therefore look similar on paper and mean quite different things on a wide web. A single light product such as this light-gauge product shows why the point matters.

The practical outcome is that tolerance is agreed per gauge rather than inherited from a general rule. If your product runs across several thicknesses, it is worth asking the supplier to confirm the band for each one separately instead of assuming that the band agreed for the heaviest gauge applies at the lightest. Both sides save time later, and the risk of a misunderstanding at the lightest gauge disappears.

Where the same logic applies to width rather than thickness, this companion note walks through the comparable decisions.

What does the tolerance band do to your material yield?

The band acts on yield from both directions: coils that run light give you less saleable material from the same running metres, and coils that run heavy make you pay for metal you may not convert.

Because the effect is gradual and depends on your conversion, treat the band as a joint calculation with your supplier.

Dive deeper

Yield is the difference between what you buy and what you sell, and the band affects it from both ends. Coils that run light give you less saleable material from the same metres of run; coils that run heavy make you pay for metal that may never become product. Neither is dramatic on its own, and both add up quietly over a season.

The band also works its way into the process in ways that are less visible in a costing sheet. A web that varies in thickness can change how a coating weighs, how a laminate bonds, how a seal forms and how consistently a slitter cuts. When a line starts producing more waste than usual, the band is one of the first things worth checking, alongside tension settings and roll condition.

Because the outcome depends on your own conversion, the honest position is that yield is a shared calculation rather than a property of the foil. Bring your running metres, your grammage and your waste figures, and the effect of moving from one band to another can be discussed in the units your finance team already uses. Ask for that comparison in writing, so both sides can revisit it when your process changes. Wider background on the material is published at alufoil.org.

How does edge-to-edge profile variation differ from a single-point reading?

A single-point reading is a snapshot taken at one place across the web. A profile describes the shape of the whole width, so it answers questions a single figure cannot.

Foil normally carries a slight crown, and the difference between a point reading and a profile shows up most on wide webs and light gauges, where the two edges must pull evenly.

Dive deeper

A single-point reading is useful, cheap and easy to quote, but it cannot tell you what is happening a hand's width away. Foil rolled on a mill naturally carries a crown: slightly thicker in the middle and tapering towards each edge, with the exact shape set by the roll camber and the way tension is distributed across the strip.

An edge-to-edge profile describes that shape. It is normally shown as a curve or as a set of readings taken at fixed positions, and for a converter it answers questions a single figure cannot: will the two edges of a wide web pull equally, will a coating sit evenly, will the roll build straight on a rewind?

The difference matters most on wide widths and light gauges. A web that is uniform in the centre but thin at one edge tends to wander on a slitter and to wrinkle when it is unwound under tension, even though its nominal thickness is exactly what was ordered. Buyers who work with wide webs therefore ask for the profile rather than the single reading, because the profile is the figure that predicts how the line will run. Where those losses tend to appear is discussed at european-aluminium.eu.

What belongs in a foil specification sheet?

A foil specification sheet should be short but complete: alloy and temper, nominal thickness, width, core, the bands that apply, and how each band will be verified.

Keep the commercial lines on the same page, and keep a copy of the version the mill confirmed, so that both sides are working from the same document.

Dive deeper

Start with the alloy and the temper, for example 1050 in the O condition or 8011 in H22, because those two lines decide the mechanical behaviour long before thickness does. Add the nominal thickness and check that it sits inside the 0.005-0.20 mm range we normally roll, together with the width you need between 100 mm and 1500 mm and the core, normally 76 mm or 152 mm.

Then write the tolerance line properly: the thickness band, the width band and the agreed method of verification. Add the surface condition, the winding direction and any interleaving, because those details affect how the coil behaves on your own equipment.

Commercial lines belong on the same page: order size, which is commonly a minimum of 3 MT per size, the loading port, which may be Qingdao, Tianjin or Shanghai, and the packing that suits your route.

Finally, keep a copy of what the mill confirmed. A specification is only useful if both sides are working from the same version. Practical reference material is published at aluminum.org.

Tolerance is not a footnote to a specification. Agree the band, agree how it is measured across the web, and your yield stops being a matter of luck.