Buying too much costs money through waste, buying too little leads to empty shelves and disappointed guests. The optimal purchase volume balances between consumption, shelf life, and inventory costs. In this article, you'll learn step by step how to calculate this for every product in your kitchen.
Why purchase volume is crucial for your profit
Many hospitality entrepreneurs buy based on gut feeling. Too much, and you throw food away. Too little, and you miss sales because you're sold out. Both cost you money.
💡 Example:
You buy 10 kg of salmon every week for €180. Consumption is 8 kg, so 2 kg goes to waste (€36 per week).
Waste per year: €36 × 52 = €1,872
By buying smartly based on actual consumption and shelf life, you prevent this waste. It saves hundreds of euros per year.
The formula for optimal purchase volume
The optimal purchase volume depends on three factors:
- Average daily consumption
- Product shelf life
- Delivery frequency
The basic formula is:
Optimal purchase volume = (Average daily consumption × Delivery interval) + Safety margin
💡 Example calculation:
Salmon: 1.2 kg per day on average, delivery every 3 days
- Base volume: 1.2 × 3 = 3.6 kg
- Safety margin (20%): 3.6 × 0.2 = 0.7 kg
Optimal purchase volume: 4.3 kg per delivery
Including shelf life in your calculation
Products with short shelf life require a different approach than long-lasting products.
Short shelf life (1-3 days):
- Fresh fish, ground meat, leafy greens
- Buy for maximum 2-3 days
- Smaller safety margin (10-15%)
Medium shelf life (4-7 days):
- Meat, vegetables, dairy
- Buy for 4-5 days
- Standard safety margin (20%)
Long shelf life (1+ week):
- Frozen goods, canned items, dry goods
- Larger volumes possible
- Higher safety margin (25-30%)
⚠️ Note:
Never calculate with maximum shelf life. Use 70-80% of the shelf life period to prevent quality loss.
Including seasons and variations
Your average consumption varies by season and day of the week. Take this into account in your purchase volume.
💡 Example variations:
Soup in winter: 40 portions/day, in summer: 15 portions/day
- Winter purchase: vegetables for 40+ portions
- Summer purchase: vegetables for 15+ portions
Adjust your purchase volume per season
Also consider:
- Weekend peaks: Friday/Saturday often 50-100% more consumption
- Holidays: different consumption patterns
- Events: temporarily higher consumption
Inventory costs vs. waste costs
The optimal purchase volume balances between two costs:
Inventory costs (buying too much):
- Waste from spoilage
- Refrigeration and storage space
- Capital tied up in inventory
Shortage costs (buying too little):
- Lost sales
- Emergency purchases at higher prices
- Disappointed guests
💡 Cost example:
Bought too little salmon, need to buy at supermarket:
- Normal purchase price: €18/kg
- Supermarket emergency purchase: €32/kg
Extra costs: €14/kg for emergency purchase
Digital tools for purchase planning
Manually tracking consumption and shelf life takes a lot of time. Digital systems like KitchenNmbrs help you:
- Automatically track consumption per product
- Monitor expiration dates
- Get purchase suggestions based on your consumption pattern
- Record and analyze waste
This gives you more time for your kitchen and guests, while keeping your purchase costs optimal.
How do you calculate optimal purchase volume? (step by step)
Measure your average daily consumption per product
Track for 2-3 weeks how much you consume daily of each product. Also include waste - that's part of your consumption. Calculate the average across all days.
Determine your delivery frequency and shelf life
Check how often your supplier delivers and what the actual shelf life is of each product. Calculate with 70-80% of the maximum shelf life for optimal quality.
Calculate base volume plus safety margin
Multiply daily consumption by delivery interval for your base volume. Add a 10-30% safety margin depending on shelf life and consumption variation.
Adjust for seasons and variations
Check if your consumption varies by season, weekday, or during events. Adjust your purchase volume accordingly to prevent shortages or surpluses.
Monitor and adjust
Check weekly if your purchase volume is correct. Too much waste? Lower the volume. Often sold out? Increase the safety margin or delivery frequency.
✨ Pro tip
Start with your 5 most expensive ingredients - if you optimize the purchase volume for those, you'll already capture 80% of your potential savings.
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
What is a good safety margin for purchase volume?
For short shelf life products (1-3 days): 10-15%. For medium shelf life products (4-7 days): 20%. For long shelf life products: 25-30%. Adjust based on your consumption variation.
How often should I adjust my purchase volumes?
Check monthly if your volumes are still correct. For seasonal products, adjust per season. For structural changes in your menu or customer base, adjust immediately.
What if my supplier has minimum order quantities?
Compare the costs of minimum orders (including waste) with alternatives like other suppliers or less frequent ordering. Sometimes a slightly higher purchase price is cheaper than a lot of waste.
How do I calculate with products I use in multiple dishes?
Add up the total consumption of that product across all dishes. For example: onions are used in soups, sauces, and as garnish. Add all these uses together for your total daily consumption.
What do I do with highly variable consumption (e.g., seasonal dishes)?
Create different purchase volumes for different periods. Summer soup: lower volume, winter soup: higher volume. Update your purchase planning with every menu change.
How do I prevent emergency purchases at high prices?
Keep a buffer for your most popular products and monitor your inventory daily. During unexpected busy times, you can quickly reorder before you run out completely.
⚠️ EU Regulation 1169/2011 — Allergen Information — https://eur-lex.europa.eu/eli/reg/2011/1169/oj
The allergen information on this page is based on EU Regulation 1169/2011. Recipes and ingredients may vary by supplier. Always verify current allergen information with your supplier and communicate this correctly to your guests. KitchenNmbrs is not liable for allergic reactions.
In the UK, the FSA enforces allergen regulations under the Food Information Regulations 2014.
📚 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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