What it means
The ratio is a screening tool with one blunt question at its heart. For every dollar this project consumes, how many dollars of value does it return?
That makes it well suited to ranking a list of competing proposals when there is not enough money to fund them all. It is heavily used in public sector and infrastructure appraisal, where benefits are often not straightforward revenue.
Time saved by commuters, injuries avoided or emissions reduced all have to be converted into dollar values before the ratio can be calculated. Private businesses use identical logic for internal projects such as a warehouse automation scheme or a safety upgrade.
The discounting step is where most of the judgement sits. Benefits and costs arriving in different years are each divided by a discount factor to bring them back to present value, and the rate you choose can move the answer materially.
A higher rate penalises projects whose benefits arrive late, which is why the rate is often argued over more fiercely than the underlying estimates. The measure is closely related to net present value but answers a different question.
Net present value tells you the size of the prize in dollars, while the benefit cost ratio tells you the efficiency of each dollar invested. A large project with a ratio of 1.15 can create far more total value than a small one with a ratio of 2.5, so the two figures should always be read together.
Two traps are worth watching for. Costs and benefits must be measured over the same period and discounted at the same rate, and ongoing operating costs should be counted as costs rather than netted off the benefits, because netting them off inflates the ratio without changing the underlying economics one bit.
In practice
Real-world examples.
Example
A city transport authority appraises a new bus lane costing $12,000,000 against $19,200,000 of discounted journey time savings and reduced collisions. The ratio of 1.6 puts the scheme ahead of a cycle bridge proposal scoring 1.1, so the bus lane is funded first.
Example
A food manufacturer weighs a $450,000 investment in vision inspection equipment against $585,000 of discounted savings from fewer product recalls and less waste. The ratio of 1.3 clears the internal hurdle of 1.2, and the project proceeds.
Example
A hospital trust evaluates a preventative maintenance contract for imaging equipment. Discounted benefits of avoided downtime and emergency repairs come to $840,000 against $700,000 of contract cost, giving a ratio of 1.2 that just justifies the commitment.
Formula
Calculation
Benefit Cost Ratio = Present Value of Benefits / Present Value of Costs
Worked example. A distribution business is considering a $3,000,000 warehouse automation project, paid in full at the start. It expects the system to save $1,200,000 a year in labour and error costs for four years, and it discounts future cash flows at 10%.
Year 1: $1,200,000 / 1.10 = $1,090,909
Year 2: $1,200,000 / 1.21 = $991,736
Year 3: $1,200,000 / 1.331 = $901,578
Year 4: $1,200,000 / 1.4641 = $819,616
Present Value of Benefits = $1,090,909 + $991,736 + $901,578 + $819,616 = $3,803,839
Benefit Cost Ratio = $3,803,839 / $3,000,000 = 1.27
Every dollar spent returns $1.27 of value in today's money. The equivalent net present value is $3,803,839 - $3,000,000 = $803,839, which tells the board the size of the gain as well as its efficiency.Case study
Seen in the real world.
Redlands Freight is a fictional haulage company used here as an illustrative example of how sensitive this measure is to assumptions. It was choosing between two proposals with the same $2,000,000 price tag: telematics across the fleet, or a depot expansion.
The telematics case showed discounted fuel and insurance savings of $3,100,000 over five years, a ratio of 1.55. The depot expansion showed discounted benefits of $2,400,000, a ratio of 1.2. On the face of it telematics won comfortably, and the operations director pushed to approve it on the spot.
The finance team then tested both at a higher discount rate, since the company's real cost of capital had risen. Telematics benefits were front-loaded and held up at 1.42, while the depot benefits, which arrived mostly in years four and five, fell to 0.98 and stopped being worth doing at all. The illustrative point is that a ratio is only as reliable as the discount rate and the timing behind it, so testing both is part of the analysis rather than an optional extra.
Watch out
Common mistakes.
- Comparing ratios calculated with different discount rates or over different time horizons, which makes the comparison meaningless.
- Netting ongoing operating costs off the benefits instead of adding them to costs, which flatters the ratio.
- Ranking projects on the ratio alone and funding several small efficient projects when one larger project would create far more total value.
Questions
People also ask.
What is a good benefit cost ratio?
Anything above 1.0 creates value in principle, but most organisations set a hurdle above that, often between 1.2 and 1.5, to allow for estimating error.
How is it different from return on investment?
Return on investment is usually a simple percentage on undiscounted figures, while this ratio explicitly accounts for the timing of money.
Can benefits that are not cash be included?
Yes, provided they are converted into credible dollar values using a stated method, which is standard practice in public sector appraisal.
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