Update a product's cost when the price of an ingredient that matters to it changes, not every time any price moves. A routine that works: compare your main ingredients on every shop, recost everything once a month, and recost straight away when a change moves your unit cost by more than you have decided to tolerate, for example 3%. For ingredients that swing with the seasons, cost with an average price instead of chasing every week at the market.
How much a price rise moves your cost
Not every rise matters equally. The calculation is:
Impact on your cost = ingredient's share of the cost × change in its price
- An ingredient that is 40% of your cost and rises 20% moves your cost 0.40 × 20% = 8%.
- An ingredient that is 3% of your cost and doubles (a 100% rise) moves it 0.03 × 100% = 3%.
Salt can double and you will barely notice. Your main ingredient rises a little and your margin goes. To know each ingredient's share you need a cost breakdown; if you do not have one, start with how to calculate the cost of a food product.
Worked example: strawberry jam
You sell 340 g jars of strawberry jam for $7.50, made from fresh fruit year-round. Here is your loaded cost per jar:
| Item | Cost | Share of cost |
|---|---|---|
| Strawberries (400 g at $4.00 a kilo) | $1.60 | 41.0% |
| Sugar | $0.30 | 7.7% |
| Lemon and pectin | $0.15 | 3.8% |
| Jar and lid | $0.85 | 21.8% |
| Label | $0.15 | 3.8% |
| Your time | $0.70 | 17.9% |
| Energy | $0.15 | 3.8% |
| Total | $3.90 |
Current margin: (7.50 − 3.90) ÷ 7.50 = 48%.
Strawberries go from $4.00 to $6.00 a kilo (a 50% rise).
- Expected impact: 41.0% × 50% = 20.5%
- New strawberry cost: 0.400 kg × 6.00 = $2.40, which is $0.80 more
- New loaded cost: 3.90 + 0.80 = $4.70 (0.80 ÷ 3.90 = 20.5% more)
- New margin: (7.50 − 4.70) ÷ 7.50 = 37.3%
You lose more than ten points of margin without changing anything in your kitchen.
Sugar rises 20%.
- New sugar cost: 0.30 × 1.20 = $0.36, which is $0.06 more
- Impact: 0.06 ÷ 3.90 = 1.5%
- New margin: (7.50 − 3.96) ÷ 7.50 = 47.2%
Less than one point. Write it down, but it is not urgent.
Set your own threshold
Decide in advance what change forces a recalculation. A reasonable starting point: recost when the unit cost moves 3% or more, or when your margin drops by more than 2 points. This is not a universal rule. It is a line you choose so that you neither recalculate for every cent nor let the important changes slip past.
Once the threshold is set, you can work out in advance which rise in each ingredient crosses it: divide your threshold by the ingredient's share.
- Strawberries: 3% ÷ 41.0% = 7.3%. A rise of about 7% in strawberries already calls for a recost.
- Sugar: 3% ÷ 7.7% = 39%. Sugar would have to rise almost 40% to cross the line on its own.
Note those two or three numbers next to your main ingredients and you will know, standing at the stall, whether a rise matters.
A routine you can keep
- Every shop: compare the price of your three to five main ingredients with the one you have recorded, always per kilo or per litre. If the pack size changed, convert before comparing; units and conversions for food costing shows how. If it crosses your threshold, recost that day.
- Once a month: recost every product with the latest prices, even if nothing crossed the threshold. Small rises add up: three ingredients rising 1.5% each are already 4.5%.
- Every three months: review what never appears on a shop receipt: energy, rent, your hourly rate, channel commissions.
- Whenever you change something yourself: recipe, supplier, packaging or size. That is a new cost too.
Seasonal ingredients
Some ingredients go up for a few months and come down for the rest of the year. If you recost and change your price every time, you confuse your customers. You have three options:
- Cost with an average price. If strawberries are $4.00 for eight months and $6.00 for four, the average is (8 × 4.00 + 4 × 6.00) ÷ 12 = $4.67 a kilo (4.667 unrounded). At that price the fruit in a jar costs 0.400 × 4.667 = $1.87, the loaded cost is $4.17 and the margin at $7.50 is (7.50 − 4.167) ÷ 7.50 = 44.4%. You earn more in the cheap months and less in the dear ones, but over the year you average that 44.4%, if you sell evenly through the year.
- Cost with the peak-season price. The safest choice: it never catches you out, but it may leave your price above competitors in the cheap months.
- Adjust the product in the expensive months. Change the recipe, sell a smaller jar, or switch to frozen fruit or a different flavour for a while.
The guide to seasonal ingredient prices shows how to plan purchases and recipes around these swings.
Recosting is not raising your price
Recosting tells you what margin you have today. What you do with it is a separate decision. You can absorb a rise you know is short, adjust your price once using the average cost, or raise it when the gap is too big to carry. If you get there, how to raise prices without losing customers covers how to do it and how to tell your customers.
Do it with the calculator
Enter your recipe with the new ingredient price in the food cost calculator and you see straight away how much the cost per unit and the margin changed. Run it again with the old price and you have the exact difference.
Frequently asked questions
Do I have to change my price every time I recost?
No. Recosting tells you what you are earning today; setting the price is a separate step. You can absorb a short rise, adjust once using an average cost, or raise the price properly, but decide knowing the number.
What if an ingredient goes up and down every week?
Do not chase every change. Cost with an average price from the last few months and review it once a month. If the average moves past your threshold, recalculate.
Which ingredients should I watch most closely?
The ones that weigh most in your cost. List each product's ingredients from most to least expensive; the top three or four usually explain most of it. Those are the ones you compare on every shop.
What if I do not have time to recost everything every month?
Start with your best sellers and the products with the thinnest margins. A product you rarely sell that earns well can wait; one you sell every day on a thin margin cannot.