Metres, kg, m² and cartons: a conversion table for the item card

If the same product is purchased in metres, held in kilograms, sold in cartons and counted in pallets, someone will convert it wrongly whichever unit the record uses. When the conversion is not written on the item card every employee makes their own calculation, and every calculation comes out slightly different. This article shows how to write the main unit, the factor and the rounding rules on the item card.

What the item card should hold

1. Main unit. The single unit in which the stock balance is kept. For fabric it may be the metre, for ceramics the m², for pipes and profiles the bar or the kg.
2. Alternative units and the factor of each to the main unit.
3. Whether the factor is fixed or variable.
4. The rounding rule.
5. Which unit is used on which document: purchase, sale and count.

The count can be done in the main unit or in whichever unit is easiest to count, but the result is written down converted to the main unit in the record. Do not leave the conversion to the counter's head; use the factor written on the card.

If the purchase unit differs from the sales unit (for example the supplier invoices in kg and you sell by the metre), both conversions belong on the card; otherwise every conversion is left to count day.

Fixed and variable factors

Fixed factors come from the packaging and stay the same as long as the packaging does. Variable ones depend on the lot or on measurement. The values below are illustrative:

• Ceramics 60×60: 1 carton = 1.44 m²; 1 pallet = 40 cartons = 57.6 m².
• Profile: 1 bar = 6 m; at 0.85 kg/m, 1 bar = 5.1 kg; 1 bundle = 20 bars = 120 m = 102 kg.
• Fabric: 1 roll is about 150 m; at 24.8 kg net, about 0.165 kg/m.

The kg/m of a fabric depends on weight per m² and width, and so on the lot, so it should be marked "by lot" on the card, and the measured metre should be the main unit. Using a variable factor as if it were fixed produces a systematic variance in the count.

The rounding rule

Rounding causes trouble in two places: in sales and in totals.

• If cartons are not split in sales, the quantity the customer wants is rounded up. For a customer wanting 50 m², 50 ÷ 1.44 = 34.72 cartons are needed; 35 cartons are supplied, and 35 × 1.44 = 50.4 m².
• In stock totals, add up the cartons (or bars) first and then convert to the main unit. Rounding every line separately and adding the results produces a difference of several square metres over a long table.
• On screen and in reports m² is shown with two decimals; the system keeps more places internally.
• When you write the rule, say on which document it applies: invoice, issue slip or count sheet.

When the factor is out of date

An illustrative case: the supplier raised the carton content of the same model from 4 tiles to 5, so a carton is now 5 × 0.36 = 1.80 m². The item card was not updated and 30 cartons were received. The record shows 30 × 1.44 = 43.2 m², while 30 × 1.80 = 54.0 m² are really there. The 10.8 m² gap appears in the count as a "surplus", but there is neither surplus nor loss, only an old factor. The gap keeps growing with every new receipt of the same lot.

The new factor may not apply to old stock, so the change should be written with its date and lot, and the factors of the old lots should not be deleted.

Who changes the factor?

• The right to change a conversion factor should sit with one or two people, and the date and reason of the change should stay in the record.
• At goods receipt, read the tiles per carton and the m² from the label and compare them with the card.
• A factor change also affects the sales price and the cost, so accounting and sales should be informed.

In short

When the unit conversion is written on the card, the count result speaks the same language as the record. In building-material warehouses StockSystem converts between pallets, cartons, m² and kg for ceramics, profiles, paint and insulation according to the item card, so that one product is not counted in two units and recorded twice.