Marginal Cost Calculator
Find your marginal cost — the cost of producing one more unit — from the change in total cost and quantity. Compare it to your selling price to see if making more still makes money.
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Learn moreMarginal cost and the profit rule
Marginal cost is the extra cost of making one more unit — the change in total cost divided by the change in quantity. Economics’ core rule: keep producing while marginal cost is below the price you get (your marginal revenue), and stop where marginal cost equals marginal revenue. That crossover is the profit-maximizing output.
How it’s calculated & sources
Marginal cost = (new total cost − old total cost) ÷ (new units − old units). Compared to your selling price (a proxy for marginal revenue).
Benchmark: the profit-maximizing rule — produce while marginal cost < price (marginal revenue); stop where MC = MR.
Results update as you type and are general estimates, not personalized advice. Verify with a professional.
Worked example
Going from 1,000 to 1,500 units raises total cost from $10,000 to $14,000 — $4,000 for 500 units, a marginal cost of $8/unit. At a $12 price, each extra unit still adds $4 of profit.
Frequently asked questions
What is the marginal cost formula?
Change in total cost divided by change in quantity: ΔTC ÷ ΔQ.
Why does marginal cost matter?
It sets your profit-maximizing output: produce while it stays below price, stop when it equals marginal revenue.
Does marginal cost include fixed costs?
No — only the additional (variable) cost of the extra units. Fixed costs don’t change with one more unit.