Last month, a chef discovered 1.8kg of missing ribeye worth €67 — the kind of loss that happens silently every week in most kitchens. Theoretical inventory shows what you should have based on sales and purchases, while actual inventory reveals what's really there. The gap between them exposes exactly where your money disappears.
What is theoretical versus actual inventory?
Theoretical inventory represents what should remain after accounting for purchases and sales. Actual inventory is what you physically count in your storage areas.
The variance reveals several costly issues:
- Waste and spoilage
- Theft (internal or external)
- Portion deviations (oversized portions)
- Registration errors
- Trimming loss you didn't account for
The formula for theoretical inventory
The calculation follows a straightforward formula:
Theoretical inventory = Beginning inventory + Purchases - Sales
You'll need precise tracking of:
- Monday's starting inventory count
- All purchases throughout the week
- Total sales volume (measured in weight, not revenue)
💡 Example:
Weekly steak tracking:
- Monday beginning inventory: 12 kg
- Tuesday purchase: 8 kg
- This week sold: 65 portions × 250g = 16.25 kg
Theoretical inventory: 12 + 8 - 16.25 = 3.75 kg
Actual inventory: count what's there
Physical counting covers every storage location:
- Cooler inventory (including opened packages)
- Freezer contents
- Dry storage items
- Prepared mise-en-place
⚠️ Note:
Include near-expired products in your count. They maintain inventory value regardless of sellability.
Calculate and interpret the difference
The variance calculation is simple subtraction:
Difference = Theoretical inventory - Actual inventory
💡 Example:
Steak calculation continued:
- Theoretical inventory: 3.75 kg
- Actual inventory (counted): 2.1 kg
- Difference: 3.75 - 2.1 = 1.65 kg shortage
At €32/kg steak = €52.80 difference this week
Understanding your results:
- Positive difference (shortage): More product disappeared than sold. Indicates waste, theft, or oversized portions
- Negative difference (surplus): More inventory than expected. Points to registration errors or undersized portions
- Zero difference: Perfect match (extremely rare)
What do you do with this information?
Variances of 5-10% fall within normal ranges, but larger discrepancies demand investigation. This is the kind of thing you only learn after closing your first month at a loss — small leaks compound quickly.
💡 Corrective actions:
- 15%+ shortage: Audit portion sizes, retrain kitchen staff on precise portioning
- Excessive spoilage: Reduce order quantities, strengthen FIFO rotation
- Consistent shortage: Investigate potential staff consumption or theft
Digital versus manual tracking
Excel spreadsheets and paper logs remain common but consume significant time and introduce errors. Systems that automatically track sales by dish simplify the process — you just count physical inventory.
The benefit: instant visibility into ingredient-specific variances enables targeted interventions rather than guesswork.
How do you calculate inventory discrepancies? (step by step)
Note your beginning inventory on Monday
Count all ingredients you want to monitor. Note per product how many kilos you have. This is your starting point for the week.
Track purchases and sales
Note everything you buy (in kilos). Count how much you sold by number of portions × portion weight. For example: 50 steaks × 250g = 12.5 kg sold.
Calculate theoretical inventory
Use the formula: Beginning inventory + Purchases - Sales = Theoretical inventory. This is what you should have.
Count actual inventory on Sunday
Physically count what's in cooler, freezer, and storage. Count everything, including opened products and mise-en-place.
Calculate the difference
Subtract actual inventory from theoretical. A positive number means shortage, a negative number means surplus. Calculate what this costs in euros.
✨ Pro tip
Track your 3 highest-cost proteins first — beef, fish, and premium cuts typically account for 60% of inventory value. Master these calculations over 2 weeks before expanding to other ingredients.
Calculate this yourself?
In the KitchenNmbrs app you can do this in just a few clicks. 7 days free, no credit card.
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Frequently asked questions
How often should I count inventory for a reliable comparison?
Weekly counting works best for main ingredients. Daily counts create excessive workload, while monthly intervals provide insufficient insight. Pick a consistent day like Sunday after closing for accurate tracking.
What is an acceptable inventory discrepancy?
Normal variance ranges from 5-10% due to natural spoilage and minor portion deviations. Shortages exceeding 15% consistently indicate problems requiring immediate attention. Fresh products like fish and vegetables naturally show higher variance rates.
How do I convert portions to kilos sold?
Multiply portions sold by net weight per portion. Remember to use post-cooking weight — a raw 250g steak weighs approximately 200g after cooking due to moisture loss. This conversion accuracy directly impacts your theoretical calculations.
📚 Sources consulted
- EU Verordening 852/2004 — Levensmiddelenhygiëne (2004) — Official source
- EU Verordening 853/2004 — Hygiënevoorschriften voor levensmiddelen van dierlijke oorsprong (2004) — Official source
- EU Verordening 1169/2011 — Voedselinformatie aan consumenten (2011) — Official source
- NVWA — Hygiënecode voor de horeca (2024) — Official source
- NVWA — Allergenen in voedsel (2024) — Official source
- Codex Alimentarius — International Food Standards (2024) — Official source
- FSA — Safer food, better business (HACCP) (2024) — Official source
- BVL — Lebensmittelhygiene (HACCP) (2024) — Official source
- Warenwetbesluit Bereiding en behandeling van levensmiddelen (2024) — Official source
- WHO — Foodborne diseases estimates (2024) — Official source
Food Standards Agency (FSA) — https://www.food.gov.uk
The HACCP standards shown in this application are for informational purposes only. KitchenNmbrs does not guarantee that displayed values are current or complete. Always consult the FSA or your local authority for the latest regulations.
Written by
Jeffrey Smit
Founder & CEO of KitchenNmbrs
Jeffrey Smit built KitchenNmbrs from 8 years of hands-on experience as kitchen manager at 1NUL8 Group in Rotterdam. His mission: give every restaurant owner control over food cost.
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