Filling and overfill calculator

It answers the filling-day questions: how many units the batch fills, how much overfill the filler needs to pass net-content checks, how much product is being given away and how many bottles, caps, labels and cases to pull. In the example, a 500 gal batch at 8.6 lb/gal with 5 gal of heel and 0.5% line loss fills 1,939 bottles of 32 fl oz in about 1.4 hours.

They set how far below the labeled quantity a package may fall before it counts as short. OIML R 87, used in Europe and many countries, gives T = 15 g or mL from 500 g to 1 kg and 1.5% from 1 to 10 kg. In the U.S., NIST Handbook 133 uses its own Maximum Allowable Variations: about 1 fl oz (29 mL) for 32 fl oz, entered in the example. The calculator applies three rules to that value: average at least the labeled quantity, no more than 2.5% of units below Qn − T and none below Qn − 2T.

It depends on your filler’s spread. The calculator takes the largest of zero, 1.96·σ − T and 3.72·σ − 2T and adds a margin in standard deviations. In the example, with σ = 0.2 fl oz and a 1 fl oz MAV, the statistical minimum is zero (the mean only needs to sit at label) and with a one-sigma margin the suggested overfill is 0.2 fl oz. The filler runs at 0.5 fl oz, so 0.3 fl oz per bottle is extra.

Weigh 30 or more consecutive units, subtract the average tare of bottle and cap (weigh a few empties) and compute mean and standard deviation, for example with STDEV in Excel. Repeat at different times of the shift, since tank level, temperature and foam change the spread. Well-adjusted volumetric fillers usually run 0.3% to 1% of fill.

In the example, 0.3 fl oz above suggested on 300,000 bottles a year adds up to about 6,050 lb of product, roughly $2,720 at $0.45/lb. With a $5,000 investment in a checkweigher or filler adjustment, payback is about 1.8 years. Even the full 0.5 fl oz overfill costs only $0.015 a bottle, but that is about $4,500 a year.

It multiplies units by each material’s loss and rounds up: in the example, 1,959 bottles (1% loss), 1,969 caps (1.5%), 1,978 labels (2%) and 164 cases of 12 (1%). At the prices entered, packaging costs $944 for the batch, or $0.487 per unit. Use your stockroom history to tune the losses.

It assumes normally distributed fills and uses specific gravity to convert volume to weight; measure density at filling temperature. Inspectors use HB 133 sampling plans and criteria that differ in detail from these rules, and some products have their own requirements, so check what applies. Foam, drips and drift over a shift call for extra margin: do not cut overfill without SPC and frequent check weighing.