Restaurant Purchase Units: Converting Cases, Kilograms and Recipe Portions
Running a restaurant usually means juggling stock that arrives in cases and sacks but leaves in recipe portions. The gap between those two units is where cost leaks quietly build up. If you can convert a purchase unit to a recipe unit correctly, you can price a plate, order more accurately, and compare suppliers on a fair basis. Here is how to do it step by step.
The three units you work with
Record three units for each ingredient:
Purchase unit – What you buy it in, usually a case, bag, or carton. The invoice shows this. Base unit – The unit you track stock in, usually kilograms or liters. Recipe unit – What your recipe actually uses, such as grams per portion.
Your job in receiving is simple: record what arrives in the purchase unit, convert it to the base unit so stock is correct, and let the recipe use the base unit in grams. When all three line up, your numbers stay honest.
Net weight versus gross weight
Before converting anything, check the label. Gross weight includes the packaging. Net weight is what is inside – the product you actually cook with. Always convert from net weight. If a 50 kg sack holds 48 kg of product, use 48 kg. Using gross weight overstates usable stock and understates the calculated cost per kilogram.
Convert a case to cost per kilogram
Work in five steps:
- Confirm the net weight on the case.
- Multiply the weight of one pack by the number of packs to get the total net weight.
- Divide the case price by the total net weight to get cost per kilogram.
- Divide your recipe's gram portion by 1000, then multiply by the cost per kilogram.
- If you calculated the cost for a whole batch, divide the batch ingredient cost by its measured portion count. Do not divide a per-portion cost again.
This gives you the raw ingredient cost of each portion before you factor in waste or yield.
A worked example
Let's use a simple hypothetical. You buy a case of 6 bags of an ingredient, each bag holding 2 kg. The whole case costs AED 180.
| Step | Calculation | Result |
|---|---|---|
| Total net weight | 6 bags x 2 kg | 12 kg |
| Cost per kilogram | AED 180 / 12 kg | AED 15/kg |
| 200 g raw portion | AED 15 x 0.2 | AED 3.00 before yield |
| 80% usable yield | 12 kg x 0.8 | 9.6 kg usable |
| Usable cost per kg | AED 180 / 9.6 kg | AED 18.75/kg |
A 200 g raw-input portion costs AED 3.00. In the separate hypothetical 80% yield example, a 200 g usable-output portion costs AED 3.75 (0.2 kg × AED 18.75/kg). These are different portion bases: match the recipe quantity to the raw or usable cost basis and do not apply yield twice.
Use yield carefully
Yield is not universal. It changes by ingredient, supplier, season, and how your kitchen trims. The 80% figure above is purely an example for one ingredient. Measure yield for the specific products you buy, and do not apply one number across your whole inventory.
Do not treat kilograms as liters
Weight and volume are different. One liter of one ingredient will not weigh the same as one liter of another. Do not treat a kilogram as a liter or a liter as a kilogram unless you have an ingredient-specific, measured density for that product. Weigh liquids on a scale, and keep each ingredient's density confirmed.
Keep the mapping consistent when the pack changes
When the supplier changes the pack size, your conversion changes with it. If the price per case stays the same but the bags shrink from 2 kg to 1.8 kg, the cost per kilogram climbs. Recalculate whenever you get a new pack size, not after a few weeks of silent margin loss.
Agree on the unit mapping before you approve
Your purchasing unit will be a case, and your recipe uses grams. Agree on this unit mapping once so every level records stock the same way, a requested approval confirms the mapping, and your kitchen database uses one consistent base unit. One quick review avoids weeks of mismatched numbers.
Frequently Asked Questions
Why does my ingredient cost keep going up when supplier prices stay the same? A smaller net pack with the same price raises your cost per kilogram. Recalculate against net weight whenever the pack changes.
Can I use the same yield for all my ingredients? No. Yield varies by ingredient and kitchen practice. Measure each product on its own.
Do I track liters as kilograms? Only when density is ingredient-specific. Otherwise keep volume and weight as separate base units.
Turning the math into your operation
Recording purchases in cases and converting to base units keeps stock accurate and recipe cost realistic. When you request a walkthrough of the purchasing and unit workflow, we can show how a purchase maps to your stock. Pair this with ingredient versus finished-goods tracking to keep the whole picture straight.
The next time you receive a case, convert it once. Let the numbers, not the assumption, run your food cost.