Seasonal portion adjustments can affect your annual food cost by 3-8% without you noticing. Many restaurants serve larger portions in winter (hearty stews) and lighter portions in summer (salads), but don't adjust their cost price calculations. In this article, you'll learn step by step how to calculate the financial impact of seasonal variations in portion sizes.
Why seasonal portions affect your food cost
Your kitchen works intuitively with the seasons. In January you serve 300 grams of stew, in July 180 grams of grilled fish. That makes sense, because guests expect it too. But if your cost price doesn't move with it, you lose sight of your margins.
💡 Example:
Your signature stew in winter:
- Beef: 300g × €24/kg = €7.20
- Vegetables and herbs: €2.80
- Garnish: €1.50
Total: €11.50 ingredient costs
💡 Example:
The same stew in summer (smaller portion):
- Beef: 200g × €24/kg = €4.80
- Vegetables and herbs: €2.80
- Garnish: €1.50
Total: €9.10 ingredient costs
The difference: €2.40 per portion. At 50 portions per month, that's €1,440 difference in cost price. If your selling price stays the same, your food cost shifts from 32% to 25%.
The three main causes of seasonal variation
- Portion size adjustments: Heavier dishes in winter, lighter ones in summer
- Ingredient substitution: Expensive winter ingredients vs. cheap summer ingredients
- Unconscious adjustments: Your chef automatically puts more/less on the plate
⚠️ Watch out:
Many restaurants calculate their food cost once a year and use that as standard. This way they miss seasonal differences of sometimes 10 percentage points.
How to measure and calculate seasonal impact
Most kitchens work with 4 seasons, but for cost purposes it's more convenient to think in 2 periods: winter menu (October-March) and summer menu (April-September).
💡 Example annual impact calculation:
You sell 2,400 portions per year of your signature dish:
- Winter (6 months): 1,200 × €11.50 = €13,800
- Summer (6 months): 1,200 × €9.10 = €10,920
Total ingredient costs: €24,720
Average cost price per portion: €24,720 ÷ 2,400 = €10.30
If you only calculated with the winter cost price (€11.50), you'd overestimate your annual ingredient costs by €2,880. If you only use summer cost price, you'd underestimate by €2,880.
Practical monitoring of seasonal differences
The most important thing is to calculate your top 5 dishes per season. These usually represent 60-80% of your food turnover.
- Calculate cost price for winter portion
- Calculate cost price for summer portion
- Note the difference per portion
- Multiply by expected number of portions per season
⚠️ Watch out:
Don't forget to include your garnishes and side dishes. An extra scoop of mashed potatoes in winter costs you €0.40 per plate, but at 100 plates per week that's €20.80 extra per week.
When price adjustment makes sense
If your seasonal cost difference is more than 15%, consider different menu prices. Many restaurants already do this unconsciously by making winter specials more expensive than summer dishes.
With a food cost difference of €2.40 per portion, you could consider making your winter version €3-4 more expensive, so your food cost percentage stays the same.
How do you calculate seasonal impact on food cost? (step by step)
Choose your top 5 seasonal dishes
Pick your 5 best-selling dishes that you make differently in winter vs summer. Think of stews, salads, soups. Count how many of each you sell per season.
Calculate cost price for both seasons
Weigh and calculate the exact ingredient costs for the winter version and summer version of each dish. Don't forget to include garnishes, sauces and side dishes.
Calculate annual impact per dish
Multiply the cost price difference per portion by the number of portions per season. Add up all dishes for your total seasonal impact on an annual basis.
✨ Pro tip
Check in March and September your actual portion weights by weighing everything that leaves the kitchen for a week. You'll often see portions deviate 10-20% from your calculation.
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
Should I use different menu prices per season?
Only if the cost price difference is more than 15%. Then you could consider making winter dishes €2-4 more expensive to keep your food cost percentage the same.
How often should I update my seasonal calculation?
At least 2x per year: when switching to winter menu (October) and summer menu (April). If your ingredient prices fluctuate heavily, then more often.
What if my chef unconsciously adjusts the portions?
Weigh your portions regularly. A kitchen scale next to the stove helps. Train your team to maintain consistent portions, regardless of season.
Does this also apply to drinks and desserts?
Yes, especially for seasonal cocktails and warm vs cold desserts. A warm chocolate cake costs more than an ice cream sundae, even if they're the same price on the menu.
How do I prevent my average food cost from being wrong?
Calculate your annual average by weighting both seasons by number of portions. Don't just use the average of winter and summer cost prices.
📚 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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