What it means
Cost sounds like an everyday word but it carries a precise accounting meaning. When a business buys a machine for $80,000 that figure is its cost, and it sits on the balance sheet as an asset until it is gradually consumed through use and charged to profit as depreciation.
The cost itself does not change just because the machine becomes more or less useful. The distinction between a cost and an expense trips up a lot of capable people.
A cost becomes an expense at the moment the value it represents is consumed, so stock bought in March but sold in June is a cost in March and an expense in June. This timing difference is exactly why a profitable month can still be a month of heavy cash outflow.
For decision making, the most useful split is between fixed and variable. Fixed costs such as rent, insurance and salaried staff stay broadly the same across a range of output, while variable costs such as materials, packaging and delivery move directly with volume.
The mix between the two determines how quickly profit rises when sales grow and how fast it collapses when they fall. Managers also separate direct from indirect costs.
Direct costs can be traced to a single product, job or customer without guesswork, while indirect costs, generally called overheads, support everything at once and must be spread across output using an allocation rule that is always somewhat arbitrary. The most valuable idea of all is that the right cost depends on the question being asked.
Historical cost answers "what did we pay", replacement cost answers "what would it take to buy this again today", and opportunity cost answers "what did we give up by choosing this option". Using the accounting figure to answer a decision question is one of the most common analytical errors in business.
In practice
Real-world examples.
Example
A coffee roaster works out that beans, packaging and postage cost $6.40 per bag while rent, roasting equipment and salaries add another $80,000 a year. That split lets the owner see instantly that any price above $6.40 contributes something towards the fixed base, even if it does not yet produce a profit.
Example
A software firm treats a $240,000 payment for a three-year server contract as a cost that becomes an expense at $80,000 a year rather than all at once. Doing so keeps the profit and loss account comparable across the three years instead of distorting the first one.
Example
A logistics business turns down a contract priced at $180 per delivery because its accounting unit cost is $195. A closer look shows that $60 of that figure is allocated head office overhead that would not change either way, so the deal actually adds $45 per delivery and the rejection cost the company money.
Formula
Calculation
Total cost = fixed costs + (variable cost per unit x units produced). Unit cost = total cost / units produced.
A small manufacturer has quarterly fixed costs of $120,000 covering rent, salaried staff and insurance. Variable cost is $18 per unit for materials, packaging and freight. In the quarter it produces 15,000 units.
Variable costs = $18 x 15,000 = $270,000.
Total cost = $120,000 + $270,000 = $390,000.
Unit cost = $390,000 / 15,000 = $26.00, made up of $18.00 of variable cost and $8.00 of fixed cost ($120,000 / 15,000).
Now raise output to 20,000 units with no new fixed costs. Variable costs = $18 x 20,000 = $360,000, total cost = $120,000 + $360,000 = $480,000, and unit cost = $480,000 / 20,000 = $24.00. The fixed slice per unit has fallen from $8.00 to $6.00, which is the whole of the $2.00 improvement.Case study
Seen in the real world.
The following is an illustrative, fictional scenario. Tallow Lane Furniture, a made-to-order workshop, priced every piece at its accounting unit cost plus 30%. Because the workshop was quiet, that unit cost included a large fixed overhead spread across very few pieces, which pushed quoted prices well above what customers would accept.
The owner separated the numbers for the first time. Materials and piece-work wages came to $340 per unit, while workshop rent, machinery and salaried staff totalled $22,000 a month regardless of output. At the then-current 40 units a month, fixed costs added $550 per unit, so full cost was $890 and the quoted price was $1,157.
Understanding the split changed the commercial strategy rather than the accounts. Tallow Lane kept its standard price for retail customers but accepted a trade order at $700 per unit, because every one of those units still contributed $360 towards the fixed base. Volume rose to 70 units a month, fixed cost per unit fell to roughly $314, and the business became profitable at prices it had previously refused on principle.
Watch out
Common mistakes.
- Using the words cost and expense interchangeably, which hides the timing difference between paying for something and consuming it.
- Treating an allocated overhead as if it would disappear when a product or contract is dropped, when the underlying spending usually just moves onto whatever is left.
- Assuming fixed costs are fixed forever, when they only hold across a limited range of activity and step up sharply once you need a second site, shift or supervisor.
Questions
People also ask.
What is the difference between cost and price?
Cost is what the business gives up to produce or acquire something, while price is what a customer pays for it, and the gap between them is the margin.
Is a sunk cost relevant to a decision?
No, money already spent and unrecoverable should be ignored when choosing between future options, however uncomfortable that feels.
Why do two accountants produce different unit costs for the same product?
Because overhead allocation depends on the chosen basis, so splitting by machine hours rather than headcount can shift thousands of dollars between products without anything real changing.
From the founder's library
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