Price per kilogram is an excellent shopping tool, but it does not always tell the whole story. Food can include bone, peel, shells, packing liquid, fat that will be trimmed or substantial cooking loss. When two formats have different yields, the apparently cheaper €/kg option can end up costing more per edible serving.

There is no need to turn every grocery trip into an accounting exercise. Understanding five ideas—unit price, drained weight, trimming loss, edible portion and final yield—is enough to make the right calculation when it matters.

Start by comparing the same unit

If two packs have different weights, price per kilogram puts them on a common basis. A 750 g pack costing €9 is €12/kg; a 1 kg pack at €11.50 is €11.50/kg. If the products are genuinely equivalent, the second is cheaper by weight.

The important word is equivalent. Net weight is not the same as drained weight, and a bone-in joint is not the same as a boneless one. A common unit only helps when the measured material is comparable.

Net weight and drained weight in preserved foods

A jar of chickpeas, asparagus or peppers may contain packing liquid. Net weight includes everything in the package, while drained weight indicates the amount of solid food remaining after the liquid has been removed according to the relevant method.

If the liquid will be discarded, drained weight is the useful buying reference. A jar costing €4.50 with 450 g drained product costs €10 per drained kilogram, even if its total net weight is much higher. Comparing it with another jar using net weight alone would distort the result.

Packing liquid is not always useless; some recipes use it. But when it goes down the sink, it should not be counted as edible yield.

Bone: purchased weight that is not a meat serving

Chops, whole poultry and bone-in cured ham contain a fraction that will not be eaten as meat. Yield converts the shelf price into the cost of the edible portion.

If one kilogram costs €15 and gives 700 g of usable meat, divide €15 by 0.70 kg: the effective cost is €21.43/kg of usable meat. Bones can be given some value if they genuinely become stock, but not simply because they could theoretically be used.

Peel, shells and other non-edible parts

Fruit, shellfish, nuts in shell and some vegetables also have very different yields. A kilogram of walnuts in shell is clearly not equivalent to a kilogram of walnut kernels, and one kilogram of oranges does not provide one kilogram of flesh.

You do not always need a published percentage. For products you buy repeatedly, weigh the discarded parts once and build a personal reference. It may be more accurate than a generic average because it reflects how you actually trim and use the food.

Preparation loss

Waste and trimming are not limited to inedible anatomy. Tough stems, external fat, dried ends, skins and unwanted tissue may all be removed during preparation. Two cooks can therefore obtain different yields from the same product.

Restaurants track this closely because small percentage changes matter at scale. At home, detailed measurement is worthwhile mainly when comparing expensive formats or buying in quantity.

Cooking loss changes the numbers again

Many foods lose water and sometimes fat during cooking. One hundred grams of raw meat does not become one hundred grams of roast meat, and vegetables can lose substantial moisture in the oven. Dry pasta and pulses do the opposite: they gain weight by absorbing water.

If the goal is to compare plated servings, the useful number is the amount ready to eat after the usual cooking method rather than the raw weight alone.

Dry foods that gain weight

Pulses, rice and pasta illustrate the reverse calculation. Their dry price per kilogram is only part of the story because the food absorbs water and yields a much larger cooked weight.

Comparing one kilogram of dried chickpeas directly with one kilogram net weight of cooked chickpeas ignores water, draining, preparation time and cooking energy. The formats solve different needs and should be compared by the serving they ultimately provide.

Cost per serving is often the clearest measure

Once yield is known, converting the purchase into servings makes decisions intuitive. A product costing €30 that provides six realistic servings costs €5 per serving. Another costing €26 but giving only four servings costs €6.50 per serving despite the lower ticket price.

Servings must be comparable—either the same gram weight or an amount fulfilling the same role in a meal. Quality and convenience may justify a premium, but at least yield is no longer hidden.

Convenience has an economic value too

Peeled, boned, sliced or cooked foods include labour. They can cost more per kilogram yet remain sensible purchases if they reduce home waste, save time or prevent spoilage. The mistake is treating a prepared format and a raw format as though they deliver exactly the same service.

A household that eats ham occasionally may waste less with small sliced packs, while a regular pulse eater may save with dried legumes. Consumption frequency changes the calculation.

One simple formula covers most cases

The basic rule is: cost per usable kilogram = price paid ÷ usable kilograms obtained. For cost per serving, divide the price by the number of real servings. Use drained weight for preserved foods when appropriate, edible weight for bone-in products and cooked yield when that is the relevant comparison.

The point is not to make shopping complicated. It is to prevent false comparisons.

Mixed gourmet products to compare in practice

Mixed packs are a good place to apply the method because their contents may have different weights and preparation levels. The value of a set depends on what each product is, how much it contains and how much will actually be used—not merely the sum of gross weights.

Gift sets and mixed packs to compare value

Price per kilogram remains the starting point, but the decisive question is “a kilogram of what?”. Bone, packing liquid, shells, trimming and cooking can change the cost of what reaches the plate. A few simple yield calculations make comparisons fairer and help identify genuine value rather than the lowest-looking label.