The benefit-cost ratio compares the present value of monetized benefits with the present value of monetized costs under a defined appraisal perspective.
The benefit-cost ratio (BCR) compares the present value of a proposal’s monetized benefits with the present value of its monetized costs. Under the basic convention, a BCR above 1 means quantified discounted benefits exceed quantified discounted costs within the model.
The ratio is a summary measure, not an automatic approval rule. It does not show project scale, affordability, distributional effects, unmonetized impacts, or whether another option better meets the objective.
Let (B_t) and (C_t) be monetized benefits and costs in period (t), and let (r) be the applicable discount rate:
Under this convention:
BCR > 1: present value of monetized benefits exceeds present value of monetized costs.BCR = 1: present values are equal.BCR < 1: present value of monetized benefits is below present value of monetized costs.The ratio is undefined or unhelpful when the denominator is zero or negative. Complex cash-flow patterns may be better summarized with NPV and a full schedule.
Two mutually exclusive projects have already been discounted using a consistent method:
| Project | Present value of benefits | Present value of costs | BCR | NPV |
|---|---|---|---|---|
| A | $1,200,000 | $1,000,000 | 1.20 | $200,000 |
| B | $3,000,000 | $2,700,000 | 1.11 | $300,000 |
Project A has the higher BCR, producing $1.20 of modeled benefit per dollar of modeled cost. Project B has the higher NPV, adding $300,000 of modeled net benefit rather than $200,000.
If only one project can be selected, choosing A solely because its ratio is higher would ignore B’s greater absolute net benefit. The decision must also consider objectives, budget capacity, risk, timing, unmonetized effects, and whether the projects truly have comparable scope.
| Measure | What it shows | Main limitation |
|---|---|---|
| BCR | Relative monetized benefit per unit of monetized cost | Can ignore scale and depend on classification |
| NPV or net present social value | Absolute net monetized value | Does not show benefit per constrained dollar |
For independent, divisible opportunities under a binding capital constraint, a ratio may help compare relative use of resources. For indivisible projects, dependencies, and multiple constraints, selecting projects by BCR alone may not maximize total NPV.
Suppose a project reduces operating cost. Analysts could classify the saving as a benefit in the numerator or as a negative cost in the denominator. NPV may remain unchanged, but the BCR can change materially.
Appraisal policy should specify treatment of:
Consistency across options and periods is more important than choosing the most favorable presentation.
A private financial appraisal generally focuses on incremental after-tax cash flows to the firm or investor. A social cost-benefit analysis uses a broader perspective and may include external effects on households, businesses, government, or the environment.
The two analyses can produce different results because they use different boundaries, prices, transfers, and discounting policies. A social BCR should not be presented as a private investment return, and a company revenue forecast should not be treated as a social benefit without considering who pays it.
This article provides general finance and appraisal education, not investment, public-policy, valuation, accounting, tax, or project-selection advice. BCR definitions and discounting should follow the applicable decision framework.