Compare Supermarket Pack Sizes When Unit Labels Differ

Capture The Exact Price And Comparison Quantity

Write the current payable price, pack description and the quantity relevant to use. Keep grams separate from millilitres unless a reliable product specification supports a conversion; equal numbers do not make mass and volume interchangeable. Check whether the two products are the same form, such as prepared versus concentrated, whole contents versus drained solids, or single items versus a multipack.

Choose one base unit that makes sense for both candidates. For foods sold by mass, £/kg or £/100g is often workable. For counted items, price per usable item may be clearer. For a concentrate, use the labelled number of standard doses only when both products define a comparable dose. Copy figures rather than relying on the bold promotional badge, which may use another basis.

Convert Pounds Per Kilogram And Per 100 Grams

To convert £/kg to £/100g, divide by ten because one kilogram contains ten groups of 100 grams. A label of £3.20/kg therefore becomes £0.32/100g. To move the other direction, multiply the £/100g figure by ten. Keep enough decimal places during the calculation and round both final figures to the same sensible precision only after the comparison.

When the shelf gives only pack price and mass, divide the price by grams and multiply by the chosen base. A £2.46 pack containing 600g costs £2.46 ÷ 600 × 100, or £0.41 per 100g. Check the calculator entry by estimating: since 600g contains six 100g portions, six lots of 41p should return £2.46. This reverse check catches misplaced decimal points.

Use Drained Weight When Liquid Is Not Part Of The Choice

For products packed in liquid, inspect whether a drained weight is stated and whether the intended comparison concerns the drained contents. Divide the payable price by that drained mass when the liquid will not be used. A 400g can with 240g drained contents is not equivalent to 400g of usable solids, so using the total weight would understate the relevant unit cost.

Compare like with like: drained mass against drained mass, or total contents against total contents when the whole medium is genuinely part of the use. Do not estimate a drained figure by sight when the label omits it. If the candidates disclose quantities on incompatible bases and no reliable specification resolves them, mark the comparison inconclusive rather than manufacturing precision.

Translate Multipacks And Concentrates Into Usable Units

For a multipack, confirm the count and the size of each unit. Divide the payable pack price by the number of equivalent usable items, not merely by the number printed largest on the front. If one pack contains differently sized pieces, compare their total relevant quantity or keep the products separate. A bonus item changes the unit count only when it is actually included in the current pack.

For concentrates, read the stated dilution or dose instructions and calculate price per standard prepared amount or stated dose. Do not compare bottle volume alone with a ready-to-use product. If one label allows a range, use the dose appropriate to the same task for both and write that assumption beside the result. More concentrated is not automatically cheaper; the stated yield and current price determine the answer.

Apply The Promotion To The Payable Basket First

Recalculate with the price that the current transaction will actually charge. For a percentage offer, confirm eligibility and apply it to the qualifying item price. For a multibuy, compare the promoted group as one transaction only if that exact group is the immediate choice being evaluated. Do not subtract a voucher that the basket rejects or allocate a basket-wide saving twice across separate products.

Write the final result as both a unit figure and cash payable, for example ‘£0.36 per 100g; £2.16 today.’ The lower unit figure answers efficiency on the chosen basis, while the cash figure shows the transaction. If qualities or product forms differ, keep that difference visible rather than announcing a mathematical winner as universally better. Save or photograph the shelf information when a large discrepancy needs checking with the retailer.

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