Build Base, Downside and Upside Scenarios

Base, downside, and upside scenarios are alternative stories about the same business period. They are most useful when the assumptions explain why results change. Adding or subtracting 10% from a final profit number hides the operational causes and can create combinations that would not occur together, such as much higher sales with no added delivery cost or capacity.

Define each scenario from operating inputs

Consider a hypothetical monthly plan. The base assumes 500 units at $40, $24 variable cost per unit, and $6,000 fixed costs. The downside assumes 350 units at $38, $25 variable cost, and the same fixed costs. The upside assumes 650 units at $42, $24 variable cost, and $7,000 fixed costs because additional capacity is needed.

The downside is not merely lower volume. It also assumes a lower selling price and a higher unit cost. Those changes need reasons, such as a planned promotion and an entered supplier quote. The upside includes a cost step, preventing the model from treating extra capacity as free. These assumptions are invented examples, not forecasts of likely outcomes.

Keep the story internally consistent

Check whether the team can deliver the units, whether inventory arrives in time, and whether the stated price applies to the whole sales mix. If the upside includes a new channel with different fees, model those fees. If the downside includes canceled orders, remove only the costs that can actually be avoided; already committed inventory payments may remain.

Build a cash schedule for each case. The upside may require more inventory and receivables before customer cash arrives, while the downside may leave stock unsold. Ranking scenarios only by operating profit can miss the one with the deepest near-term cash trough.

Use the cases to prepare decisions

For each scenario, identify an observable signal, a response, and the time required to implement that response. A capacity expansion needed next month may require a decision this week. Waiting for the final monthly profit number can make the scenario exercise too late to influence the outcome.

Do not assign probabilities unless there is a defensible basis for them, and do not call the base case guaranteed or the most likely case merely because it sits in the middle. Preserve the downside loss and record the assumptions that distinguish all three cases. Update the scenarios as evidence changes, while retaining the prior version for comparison.

Method references: OpenStax: Break-Even Sensitivity Analysis. Accessed October 22, 2026. All dollar figures are hypothetical worked examples.