What Is Marginal Revenue?
Marginal revenue represents the incremental change in total revenue when you produce and sell one additional unit. It differs fundamentally from average revenue per unit because it isolates the financial impact of the marginal sale.
Consider a bakery selling 500 loaves weekly for $3,000 revenue. If production increases to 520 loaves and revenue reaches $3,180, the marginal revenue is $180 ÷ 20 units = $9 per unit. This may differ significantly from the average price per loaf, especially in markets where volume discounts or price reductions are necessary to move extra inventory.
Marginal revenue can be positive (expanding sales is profitable) or negative (discounting to sell more units erodes total revenue). Tracking this metric helps managers decide whether to scale production or maintain current output levels.
Marginal Revenue Formula
The fundamental equation for marginal revenue divides the change in total revenue by the change in quantity sold:
Marginal Revenue = Change in Total Revenue ÷ Change in Quantity
MR = ΔTR ÷ ΔQ
ΔTR = Final Revenue − Initial Revenue
ΔQ = Final Quantity − Initial Quantity
MR— Marginal revenue: additional income from selling one more unitΔTR— Change in total revenue: difference between final and initial revenue figuresΔQ— Change in quantity: difference between final and initial units soldFinal Revenue— Total sales value at the higher production or sales levelInitial Revenue— Total sales value at the baseline production or sales levelFinal Quantity— Total units sold or produced at the new levelInitial Quantity— Total units sold or produced at the baseline level
Calculating Marginal Revenue: Worked Example
Suppose a furniture manufacturer currently produces 400 dining tables per month, generating $80,000 in revenue at $200 per table. After expanding capacity, production rises to 480 tables and revenue reaches $92,400.
Step 1: Calculate change in revenue: $92,400 − $80,000 = $12,400
Step 2: Calculate change in quantity: 480 − 400 = 80 units
Step 3: Divide change in revenue by change in quantity: $12,400 ÷ 80 = $155 marginal revenue per table
This result reveals that selling each additional table brings $155 in revenue, despite the average price being $192.50 ($92,400 ÷ 480). The difference suggests that price reductions were needed to move the extra 80 units, reducing the marginal revenue below the average selling price.
Why Marginal Revenue Changes Across Output Levels
Marginal revenue typically declines as production expands due to market dynamics and pricing constraints. In competitive markets, suppliers cannot raise prices without losing customers to rivals. In monopoly or limited-supply scenarios, a business must cut prices to stimulate demand for additional units.
At low production volumes, marginal revenue often remains robust because each new sale reaches eager customers willing to pay full price. As output surpasses market demand, selling incremental units requires price reductions that erode revenue per unit. A beverage bottler selling 1,000 cases monthly at $50 each might see marginal revenue of $45 per case when scaling to 1,100 cases—but only $20 per case when expanding to 2,000 cases, as retailers demand steeper discounts for bulk orders.
Understanding this relationship informs optimal production decisions: expanding output is profitable only when marginal revenue exceeds marginal cost.
Key Considerations When Analyzing Marginal Revenue
Avoid common pitfalls when interpreting marginal revenue data and making production decisions.
- Distinguish marginal from average revenue — A high average price per unit masks the reality that extra sales may carry much lower marginal revenue. Always compare marginal revenue to marginal cost, not average cost, to evaluate expansion decisions.
- Account for negative marginal revenue — When marginal revenue turns negative, selling more units actually reduces total revenue. This occurs when price cuts required to shift additional inventory exceed the revenue from those units. Stop expanding output at this inflection point.
- Monitor market conditions continuously — Demand fluctuates seasonally, competitively, and cyclically. Marginal revenue calculations reflect specific time periods; recalculate regularly rather than relying on historical averages, especially in volatile industries.
- Include all cost implications — Lower prices to boost volume often trigger increased shipping, storage, and handling costs. Ensure your marginal revenue analysis accounts for total marginal cost, including logistics and working capital, not just production expenses.