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What is Cost Benefit Analysis and How Do You Do It?

August 18, 2026

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What is Cost Benefit Analysis and How Do You Do It?

Tuesday, 18 August 2026

Key takeaways

Cost benefit analysis compares the full costs and benefits of a decision in monetary terms so options can be ranked on net value.
Across Australia and New Zealand it is a formal expectation behind major public spending, regulatory decisions and procurement business cases.
A sound analysis follows a set sequence: define options, value the costs and benefits, discount to present value and compare the results.
The answer is only as reliable as its assumptions, so discounting and sensitivity testing decide its credibility.
For procurement professionals it underpins value for money and whole life costing rather than a focus on the headline price.

Cost benefit analysis (CBA) is a structured method that compares everything a decision will cost against everything it will deliver, expressed as far as possible in a single monetary measure. It lets decision makers rank competing options on net value, showing whether the benefits of a proposal outweigh its costs and by how much.

The technique sits behind business cases, infrastructure proposals, regulatory decisions and procurement choices across both the Australian public and private sectors. This guide explains what cost benefit analysis is, why it carries formal weight in Australia and how the method works in practice.

What is cost benefit analysis?

Cost benefit analysis is a method of evaluation that estimates and compares the total costs and benefits of a proposal, converting them into monetary terms so their net effect can be measured. Where the benefits exceed the costs, the proposal improves overall welfare. It weighs the effects on the whole community rather than on one group alone.

The most useful working definition treats cost benefit analysis as a whole of society appraisal rather than a narrow financial sum. The NSW Government Guide to Cost Benefit Analysis describes it as a holistic appraisal that estimates the economic, social, environmental and cultural costs and benefits of an initiative and expresses them in monetary terms. That framing matters because it captures effects that never appear on an accounting ledger, such as travel time saved, health outcomes or environmental damage avoided. Understood this way, the technique measures value to the community as a whole rather than cash flow to a single organisation.

For Australian organisations, this means cost benefit analysis is not an accounting exercise bolted onto a budget, but a decision tool that tests whether a proposal genuinely leaves the community better off.

Why does cost benefit analysis matter in Australia?

In Australia cost benefit analysis is not optional analytical polish, it is a formal expectation behind major public decisions. The Office of Impact Analysis, which sits within the Department of the Prime Minister and Cabinet, requires a formal cost benefit analysis for any policy proposal expected to have a substantial or widespread impact on the economy. To keep those analyses consistent and comparable, its 2023 guidance sets a common real discount rate of 7 per cent, with sensitivity testing at lower and higher rates. This discipline stops agencies from choosing the option that looks cheapest today and pushes them to account for costs and benefits that land years into the future. The practical effect is that anyone preparing a serious public proposal in Australia is expected to show their reasoning in cost benefit terms.

How do you do a cost benefit analysis?

A cost benefit analysis is built step by step rather than estimated in a single pass. The method starts by defining the problem and the options that could address it, each measured against a base case that describes what would happen with no new action. Infrastructure Australia, whose Guide to economic appraisal treats cost benefit analysis as the standard technique for weighing the merit of a proposal, structures the work around this base case and a shortlist of at least two options so each can be judged on the difference it makes. From there you identify every material cost and benefit, value them in dollars where you can, then discount future amounts back to their present value so money spent or gained in ten years is comparable with money today. The options are then compared using two summary measures. Net present value (NPV) is total benefits minus total costs. The benefit cost ratio (BCR) divides benefits by costs. An option with a positive net present value and a benefit cost ratio above one is, at least on the surface, an efficient use of resources and forms the analytical core of any business case.

What makes a cost benefit analysis credible?

A cost benefit analysis is only as trustworthy as the assumptions underneath it, so the treatment of time and uncertainty decides its credibility. The Office of Impact Analysis addresses this by requiring a consistent discount rate and sensitivity analysis, so results do not hinge on a single optimistic view of the future. Sensitivity testing reruns the analysis with higher and lower assumptions to show how robust the conclusion really is, while benefits that cannot easily be converted to dollars, such as cultural value or community wellbeing, are described clearly rather than quietly dropped. A credible analysis is transparent about what it has measured, what it has estimated and what it has left in qualitative terms.

Where does cost benefit analysis fit in procurement?

For procurement and contracting professionals, cost benefit analysis underpins the search for value for money rather than the lowest quoted price. The Commonwealth Procurement Rules make value for money the core rule of Australian Government buying and state that price is not the sole factor, requiring officials to weigh both the financial and the wider costs and benefits of each offer. This is where whole life costing comes in. The Chartered Institute of Procurement & Supply (CIPS) describes whole life costing, also known as total cost of ownership (TCO), as assessing the full cost of a product or service from acquisition through use to disposal rather than the purchase price alone. Applying that lens, a cheaper asset with high running and disposal costs can prove more expensive across its life than a dearer alternative. Read together, these frameworks show that sound procurement decisions rest on the same logic as cost benefit analysis, comparing total costs against total value over the whole life of a commitment.

Building cost benefit analysis capability with AcademyGlobal

Cost benefit analysis is a learnable discipline and the fastest way to build it is through applied practice on real business cases. AcademyGlobal (AG), a Sydney based professional development provider and an approved Chartered Institute of Procurement & Supply study centre for Australia, New Zealand and Southeast Asia, teaches the technique across its procurement, finance and business case programs. To move from understanding the method to applying it with confidence, explore AG’s Cost Benefit Analysis Fundamentals course, which walks you through building and defending a full analysis on a real world case study. The Business Case Fundamentals workshop extends this into developing the financial case for change, an options analysis and a clear recommendation for stakeholders.

For public sector teams, programs such as Procurement for NSW Public Sector and AG’s wider Procurement and Contract Management and Finance, Risk and Project Management portfolios place cost benefit thinking inside the value for money and probity frameworks that govern government spending. Delivered in partnership with UQ Skills at the University of Queensland and certified through bodies including the Australasian Procurement and Construction Council, these programs connect the method to the standards Australian organisations actually work to. Learned well, cost benefit analysis turns difficult spending decisions into transparent and defensible choices and gives professionals the confidence to invest with purpose.

Frequently asked questions

What is the difference between cost benefit analysis and cost effectiveness analysis?

Cost benefit analysis puts a dollar value on both the costs and the benefits of an option so it can report a net result. Cost effectiveness analysis is used when benefits are hard to monetise and instead compares the cost of achieving one unit of an outcome, such as the cost per additional year of healthy life.

What discount rate should a cost benefit analysis use in Australia?

For Commonwealth proposals the Office of Impact Analysis sets a real discount rate of 7 per cent, with sensitivity testing at lower and higher rates. States such as New South Wales publish their own rates, so the correct figure depends on whose guidance applies to the decision.

What counts as a good benefit cost ratio?

A benefit cost ratio (BCR) above one means the benefits of an option exceed its costs in present value terms. The higher the ratio, the more value the option returns for each dollar spent, though the quality of the underlying assumptions matters as much as the number itself.

Is cost benefit analysis required for government projects in Australia?

For Australian Government proposals expected to have a substantial or widespread impact on the economy, the Office of Impact Analysis requires a formal cost benefit analysis. State and territory frameworks set their own thresholds. Most major public business cases are expected to include one.