Free Marginal Cost Calculator
Find the extra production cost per additional unit. Choose a quick calculation, compare several production levels, or model an expansion with a new fixed expense.
All costs are in US dollars (USD). Production quantities are whole units.
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Your Results
Enter values, then select Calculate.
Enter total costs for at least two output levels in strictly increasing quantity order. Each marginal-cost result covers the interval between the current row and the previous row.
Production Results
Calculate the table to see results.
Estimate the cost of producing additional units. This mode assumes variable cost per unit is constant and includes an optional one-time fixed cost triggered by expansion.
Expansion Results
Enter values, then select Calculate.
What Is Marginal Cost?
Marginal cost measures how much total cost changes per additional unit produced. It is useful for evaluating production increases and comparing the costs of different output ranges.
Marginal Cost Formula
Marginal Cost = (New Total Cost − Old Total Cost) ÷ (New Quantity − Old Quantity)
For example, if producing 100 units costs $1,200 and producing 110 units costs $1,400, total cost rises by $200 and output rises by 10 units. Marginal cost is $20 per additional unit across this interval.
How to Use the Three Modes
Basic: Enter the change in total cost and additional units.
Production Table: Enter costs at several output levels to compare consecutive intervals. The first row has no previous interval.
Advanced: Enter current fixed costs, variable cost per unit, an expansion-only fixed expense if applicable, and old and new quantities.
Marginal Cost vs. Average Total Cost
Average total cost equals total cost divided by quantity at one production level. Marginal cost compares two different levels. In the example above, average total cost at 110 units is approximately $12.73, while the marginal cost of increasing output from 100 to 110 units is $20 per unit.
Do Fixed Costs Affect Marginal Cost?
Fixed costs that remain unchanged cancel when subtracting old total cost from new total cost. However, a new setup charge or capacity expense caused by an expansion should be included. The advanced calculator accounts for this type of extra fixed cost.
How to Interpret Your Results
Compare the extra cost of production with the extra revenue the additional products may generate. A low marginal cost alone does not guarantee profitability. Check expected demand, inventory risk, selling expenses, and other relevant business costs before changing production.
Frequently Asked Questions
What is the marginal cost formula?
Marginal cost equals the change in total cost divided by the change in production quantity: MC = ΔTC ÷ ΔQ.
How do I calculate marginal cost for one more unit?
Subtract total cost at the current output level from total cost after producing one more unit. Because quantity increases by one, the total-cost difference is the marginal cost of that unit.
Can marginal cost be negative?
Yes, a recorded decrease in total cost alongside rising production can produce a negative result. Check whether your figures use consistent accounting assumptions and time periods.
What happens when quantity does not increase?
Marginal cost per additional unit is undefined when the change in quantity is zero. The calculator requires a positive increase in output.
Is marginal cost the same as average cost?
No. Average cost is total cost divided by total output. Marginal cost measures the cost change per additional unit between two output levels.
Should I include new fixed costs?
Include fixed expenses triggered by increasing output. Fixed costs that stay unchanged cancel out of the marginal cost calculation.
Why is the first production-table marginal cost blank?
The first row has no previous output level to compare with, so an interval marginal cost cannot be calculated for that row.
Can I download the production results?
Yes. Select Calculate Table, then Download CSV. If you edit any value, recalculate before exporting the updated results.