Opportunity cost: what it is, with examples
You have a free Saturday. You can go to a concert or work a shift. Whatever you pick, you lose the other. That lost option has a name in economics, and it is the idea behind almost everything else in the subject.
Why every choice has one
Time, money and materials are limited. Economists call this scarcity. Because you cannot have everything, choosing one thing means not choosing another. The thing you lose is the cost that does not appear on any receipt.
Example 1: the concert
A ticket costs $30. But the same evening you could have worked a shift and earned $80. Going to the concert costs you $30 in cash and $80 in pay you miss: $110. The $80 is the opportunity cost of going.
Notice the trap: if the shift pays $80, a friend who has no job offer pays only $30 for the same ticket. Same concert, different opportunity cost.
Example 2: a fishing village
Nora and Tomas live in a small fishing village. Each has 8 hours a day and can spend them baking bread or catching fish. Nora bakes 4 loaves an hour, or catches 1 fish an hour. Tomas bakes 1 loaf an hour, or catches 2 fish.
If Nora spends all 8 hours baking, she makes 32 loaves. If she spends all 8 fishing, she gets 8 fish. Every hour moved from bread to fish costs her 4 loaves and gives her 1 fish. So for Nora:
For Tomas it is very different. One more fish costs him only half a loaf (an hour of fishing gives 2 fish and loses 1 loaf). The same fish is "cheap" for Tomas and "expensive" for Nora. Opportunity cost depends on the person.
| Nora | Tomas | |
|---|---|---|
| 1 fish costs | 4 loaves | ½ loaf |
| 1 loaf costs | ¼ fish | 2 fish |
This is why Tomas should fish and Nora should bake, and why trade can leave both better off. That story has its own name, comparative advantage, and it is the next step in the lesson linked below.
How to find an opportunity cost
- List your real options for that time or money.
- Pick the best one you did not choose.
- Measure it in what you gave up: dollars, hours, loaves, fish.
Other everyday cases: a year of college costs tuition plus the salary you could have earned; a farmer who plants corn on a field gives up the wheat it could have grown; a city that builds a park on a lot gives up the apartments.
The trap on tests
Two mistakes come up again and again. First, adding up all the alternatives: if you could go to the concert, work, or visit a friend, the cost of the concert is the best of the other two, not both. Second, forgetting time: "It was free" is almost never true when it took two hours you could have used.
Quick check
1. A ticket costs $30, you could earn $50 in the same evening or spend it with a friend (worth $20 to you). What is the opportunity cost of going?
The cash is $30, and the best alternative is the $50 shift, so the cost is $30 + $50 = $80. The friend option ($20) does not add: only the best alternative counts.
2. Nora moves 2 hours from baking to fishing. What does she give up, and what does she get?
She gives up 8 loaves (2 × 4) and gets 2 fish. Each fish costs her 4 loaves.
3. Tomas says "the fish cost me nothing, I caught them myself." What is wrong?
Catching fish took hours. Each hour of fishing meant one loaf he did not bake. The fish cost him half a loaf each, even with no money changing hands.