Imagine you own a pizza shop. The rent you pay for the shop every month is a fixed cost – it stays the same whether you sell 10 pizzas or 100 pizzas. It doesn’t change with the amount of pizza you make.
Variable costs are like the ingredients and the hourly wages of the chefs. The more pizzas you bake, the more dough, cheese, and labour you need. So VC rises as output rises.
Total cost is simply the sum of fixed and variable costs. If you bake 50 pizzas, you add the rent to the cost of 50 pizzas’ ingredients.
Average cost tells you how much each pizza costs on average. It’s useful when you want to set a price that covers all costs.
Marginal cost is the extra cost of making one more pizza. If the oven is already hot, the cost of the next pizza might be low; if you’re running out of cheese, it could be high.
| Cost Type | Definition | Example |
|---|---|---|
| Fixed Cost (FC) | Costs that do not change with output level. | Rent of factory, salaries of permanent staff. |
| Variable Cost (VC) | Costs that vary with output level. | Raw materials, hourly wages. |
| Total Cost (TC) | Sum of FC and VC. | \$TC = FC + VC\$. |
Revenue is the money you get from selling your pizzas. If you sell each pizza for \$5 and bake 100 pizzas, TR = \$5 × 100 = $500.
Profit is what’s left after you pay all costs. If TR = \$500 and TC = \$450, then π = $50. That’s the money you can keep or reinvest.
In the short run, at least one factor of production is fixed. Think of your pizza shop: you can’t instantly get a bigger oven or hire more permanent staff. You can only adjust how many pizzas you bake with the existing equipment.
In the long run, all factors are variable. You can build a new factory, buy a bigger oven, or hire more chefs. You’re free to change the scale of production to find the most efficient size.
Because some costs are fixed in the short run, the shape of the cost curves differs:
| Cost Curve | Short‑Run Feature | Long‑Run Feature |
|---|---|---|
| Average Cost (AC) | U‑shaped, starts high due to FC. | Flatter, can be lower as FC spreads over more units. |
| Marginal Cost (MC) | Crosses AC at its minimum. | Crosses long‑run AC at its minimum. |
| Total Cost (TC) | Increases with output, but includes fixed portion. | All costs variable, so TC can be lower for the same output. |
Remember: In the short run you’re stuck with some fixed costs, but in the long run you can adjust everything to find the most efficient scale. This is why firms plan for the long run even if they’re operating in the short run right now.