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Marginal cost tells a business how much its total production cost changes when it makes additional products. It helps businesses evaluate extra orders, production levels, and pricing decisions.
Core idea
Additional cost
Example: total cost increases from ₹1,000 to ₹1,120 when output increases from 10 to 11 units.
Extra cost
₹120
Extra units
1
In this example, the marginal cost of the 11th unit is ₹120. The figures are illustrative.
The concept
Marginal cost is the change in total production cost caused by producing additional output. It can be calculated for one extra unit or as an average across several additional units.
Measures the extra production cost associated with more output.
Compare costs at two different production levels to calculate the change.
Helps assess whether producing more units is financially worthwhile.
Important: marginal cost is not necessarily the selling price of a product. It is a production-cost measure. A business also considers demand, revenue, available capacity, and other costs when deciding whether to expand output.
Calculation
The formula compares the change in total cost with the change in quantity produced.
The formula
Subtract the original total cost from the new total cost.
Subtract the original quantity from the new quantity.
MC = ₹120 ÷ 1 = ₹120 per unit
Worked examples
These illustrative examples show how businesses can calculate marginal cost using changes in total cost and output. The figures are examples, not reported market prices.
A bakery increases production from 20 cakes to 21 cakes in one day.
Original total cost
₹4,000
20 units
New total cost
₹4,180
21 units
Change in total cost
₹180
Change in output: 1 unit
Calculation
₹180 ÷ 1 = ₹180 per additional unit
Where the extra cost comes from
The 21st cake adds ₹180 to total production cost. Its marginal cost is ₹180.
A printing business increases an order from 100 shirts to 120 shirts.
Original total cost
₹12,000
100 units
New total cost
₹14,600
120 units
Change in total cost
₹2,600
Change in output: 20 units
Calculation
₹2,600 ÷ 20 = ₹130 per additional unit
Where the extra cost comes from
The additional 20 shirts cost ₹2,600, giving an average marginal cost of ₹130 per extra shirt.
A workshop increases its daily production from 30 metal racks to 40.
Original total cost
₹18,000
30 units
New total cost
₹22,500
40 units
Change in total cost
₹4,500
Change in output: 10 units
Calculation
₹4,500 ÷ 10 = ₹450 per additional unit
Where the extra cost comes from
The extra 10 racks cost ₹4,500, so the average marginal cost is ₹450 per additional rack.
Visual explanation
Marginal cost can change as production expands. A business may initially use its existing equipment more efficiently, but later face overtime, capacity limits, or bottlenecks.
This illustrative curve shows marginal cost falling at first and then rising as production expands. Actual business cost patterns vary.
1. Falling
Better use of equipment or workers may reduce the extra cost.
2. Lowest point
Production may be operating efficiently at this output level.
3. Rising
Overtime, congestion, or limited capacity may increase extra costs.
Comparison
Both measures help businesses understand production costs, but they answer different questions.
| Basis | Marginal cost | Average cost |
|---|---|---|
| Meaning | Change in total cost divided by change in output. | Total cost divided by total output. |
| Main question | How much does additional production cost? | What is the cost per unit across all units? |
| Formula | Change in total cost ÷ change in quantity | Total cost ÷ total quantity |
| Example use | Evaluating an additional order. | Calculating the overall production cost per unit. |
Average cost example
₹1,000 ÷ 10 = ₹100
If producing 10 units costs ₹1,000 in total, average cost is ₹100 per unit.
Marginal cost example
₹120 ÷ 1 = ₹120
If the 11th unit increases total cost by ₹120, its marginal cost is ₹120.
Business decisions
Marginal cost is useful when comparing the extra cost of production with the expected additional revenue and other practical constraints.
A business can estimate the additional production cost before accepting an order. It should also check the offered price, delivery expenses, available capacity, and any extra fixed costs.
Tracking marginal cost across different output levels can help a business identify when production is becoming more expensive.
A manufacturer may compare an additional order's revenue with its extra costs. The decision must also account for other expenses and the effect on existing customers.
If overtime or extra machinery is needed, marginal cost may rise. A business can compare these extra costs with the expected benefit of higher output.
Suppose an additional unit costs ₹120 to produce and can be sold for ₹170. The difference is ₹50 before considering other additional expenses, taxes, capacity costs, and any impact on other sales. This does not automatically mean the unit will generate ₹50 in final profit.
Common errors
Use consistent cost and output figures when calculating marginal cost.
Subtract the original total cost from the new total cost before applying the formula.
Marginal cost uses the change in quantity. Dividing total cost by total quantity calculates average cost.
Extra production may become cheaper or more expensive depending on efficiency, input prices, and capacity.
Marginal cost measures production cost, while selling price is the amount charged to the customer.
Frequently asked questions
Marginal cost is the additional cost of increasing production. It shows how much total cost changes when a business produces more units.
Marginal cost equals the change in total cost divided by the change in quantity produced.
It can be zero in particular situations if additional output does not change measured total cost. In practice, businesses should check whether any extra materials, energy, labour, or other costs have been omitted.
No. Marginal cost measures the cost change associated with additional output. Average cost is total cost divided by total output.
Marginal cost may rise when a business reaches capacity limits, needs overtime, experiences bottlenecks, or pays more for additional inputs.
It helps businesses evaluate additional production, compare extra costs with expected revenue, and plan output. It is one factor in a decision, not a guarantee of profit.
Marginal cost measures the change in total production cost relative to the change in output. Calculate it by comparing two production levels, then use the result alongside expected revenue, other expenses, and capacity constraints to make better business decisions.
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