How much more must a discount sell?

How the calculation works

promoPrice = regularPrice * (1 - discountPct / 100)

regularUnitContribution = regularPrice - unitCost

promoUnitContribution = promoPrice - unitCost

requiredUnits = (baselineUnits * regularUnitContribution + campaignCost) / promoUnitContribution

requiredUnitLiftPct = (requiredUnits / baselineUnits - 1) * 100

The target is an accounting threshold. It does not predict whether customers will buy the required additional volume.

A worked example

With a €50 price, €25 variable cost and 20% discount, contribution per unit falls from €25 to €15. Matching 1,000 full-price units requires 1,666.67 discounted units before campaign spending: 66.67% more. Adding €300 campaign spending raises the target to 1,686.67 units, or 1,687 whole units.

Use it carefully

• The conventional break-even comparison requires regularPrice > unitCost and promoUnitContribution > 0.
• If promotion contribution per unit is zero or negative, selling more discounted units cannot recover a positive baseline contribution under these assumptions.
• Calculate with full precision, display exact required volume and also round up for a whole-unit target.
• For zero fixed campaign spending, the additional-sales fraction simplifies to discount / (initial contribution margin - discount), with both terms expressed as fractions of price.
• This calculation assumes unchanged variable cost per unit and no lost sales elsewhere or later.

Common questions

Does a 20% discount require 20% more sales?

Usually much more. At a 50% initial contribution margin, a 20% discount requires 66.67% more units before extra campaign spending.

What happens when the discounted price equals unit cost?

Each extra unit adds zero contribution. No finite sales increase recovers a positive full-price baseline without other benefits or funding.

Related calculations

Further context: Shopify: product margin calculation. Equations and examples were independently prepared for this calculator.