Interactive tool

Budget Line Visualizer

See which bundles are affordable and how income or prices rotate and shift a budget line.

Formula and input boundaries reviewed 9 October 2026

Controls

Income Price of good A Price of good B Preferred units of A Preferred units of B

Result

Maximum A—

Maximum B—

Opportunity cost of A—

Preferred bundle—

How the calculation works

The budget constraint is income = price of A × units of A + price of B × units of B. The horizontal intercept is income divided by the price of A; the vertical intercept is income divided by the price of B. The opportunity cost of one additional unit of A is price A divided by price B, measured in units of B.

The model assumes only two goods, fixed prices, a fixed spending budget, and divisible quantities. It does not include taxes, borrowing, bulk discounts, uncertainty, or changing preferences.

Try these scenarios

Double income with both prices fixed: the line shifts outward in parallel.
Raise only the price of A: the horizontal intercept moves inward and the line rotates.
Enter a bundle just beyond the line: its cost exceeds income and the marker turns red.

Related lesson

Consumer ChoiceOpen activity →

Sources and scope

OpenStax, Principles of Economics 3e, 6.1 Consumption Choices: budget constraints and opportunity cost.

Results are deterministic teaching calculations, not forecasts or financial advice. Displayed values are rounded; affordability is calculated from the unrounded inputs.