Overview
Enter the change in total cost and the change in quantity produced to calculate marginal cost: Δ total cost ÷ Δ quantity. This is the additional cost of producing one more unit of output, a core concept for pricing and production decisions - if marginal cost is below the selling price, producing more units generally adds to profit; if it rises above the selling price, additional production starts eating into profit. The change in quantity can be negative if you're comparing a decrease in output, and the result is computed either way rather than blocked; it just cannot be exactly zero, since it's the denominator. Runs entirely client-side, and this is an informational estimate, not financial advice.
Best for: Estimating the additional cost of producing one more unit of output
How to use this tool
- Enter the change in total cost. How much total production cost changed between the two output levels being compared.
- Enter the change in quantity. How many additional (or fewer) units were produced - cannot be zero.
- Read the marginal cost. The cost per additional unit produced.
Frequently asked questions
Yes - if you're comparing a decrease in output, enter a negative change in quantity and the calculator will compute the result accordingly rather than blocking it. It only rejects a change of exactly zero, since that would be division by zero.
A business generally benefits from producing additional units as long as marginal cost stays below the price each unit sells for. Once marginal cost rises above that price - which is common as production scales and resources get stretched - additional output starts reducing overall profit.
Average cost is total cost divided by total units. Marginal cost only looks at the cost of the next unit (or batch), which can be very different from the average - especially in businesses with high fixed costs, where marginal cost is often much lower than average cost.