Business investment calculator

Build vs Buy Calculator

Compare implementation, recurring cost, and delay before choosing build or buy.

Reviewed Jul 24, 2026

By the ROI Calculator Hub editorial team

Your assumptions

Currency

Build upfront cost

Design, engineering, testing, security, and launch.Build annual operating cost

Maintenance, infrastructure, support, and retained team capacity.Additional build delay

Months before the build option delivers value relative to buying.Monthly value delayed

Benefit or avoided cost unavailable during the extra delay.Buy setup cost

Implementation, integration, migration, and training.Buy annual operating cost

Subscription, usage, vendor support, and internal operations.Comparison period

Years of recurring cost included for both options.

Estimated result

Buy savings versus build

$70,000

Build totals $950,000; buy totals $880,000; delay accounts for $200,000.

Decision check: Buying has the lower modeled total cost

Total build cost: $950,000
Total buy cost: $880,000
Opportunity cost of build delay: $200,000
Estimated cost break-even: 6

Three-case comparison

Downside applies an unfavorable 10% change to key drivers. Upside applies a favorable change.

Case	Buy savings versus build
Downside	-$131,000
Current	$70,000
Upside	$275,000

Sensitivity check

Estimated primary-result improvement from a favorable 10% change in one driver.

Build upfront cost+42.9%
Build annual operating cost+64.3%
Additional build delay+28.6%
Monthly value delayed+28.6%

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Decision scope

What this calculator answers

Build-versus-buy decisions are often reduced to engineering cost versus subscription price. That misses implementation, long-term operations, and the economic value postponed while a custom solution is developed. This calculator compares total cost over a chosen period and makes the opportunity cost of additional build delay explicit.

Transparent math

How the calculation works

Total option cost = Upfront cost + Recurring cost + Opportunity cost of delay

The build option combines upfront development, annual operation, and monthly opportunity value lost during additional delay. The buy option combines setup and recurring vendor cost. Subtracting total buy cost from total build cost shows which option is cheaper in the modeled period. A cost break-even is estimated when recurring-cost differences allow one.

Worked example

Put the result in context

A custom build costs $300,000 upfront and $90,000 each year to operate. If it launches eight months later than a purchased option and delays $25,000 of monthly value, delay adds $200,000 to its economic cost. The model compares that total with an $80,000 setup and $160,000 annual buy cost over five years.

Methodology

Make the estimate defensible

01Use fully loaded internal engineering and operating cost.
02Value only the portion of delayed benefit that is credible and time-sensitive.
03Apply the same comparison period and functional scope to both options.

Interpretation

What counts as a good result?

Cost is only one dimension. Build may be justified by strategic differentiation, control, data constraints, or vendor risk. Buying may reduce time to value and implementation risk. Record the non-financial constraints separately and rerun the model when scope or vendor pricing changes.

Read before deciding

Limitations

Quality, strategic differentiation, switching cost, and vendor concentration are not scored.
The model does not discount future costs or model changing team size and usage tiers.
Break-even years are unavailable when recurring-cost differences cannot recover the upfront gap.

How this calculator is reviewed

We test the formula against worked examples, document which costs belong in the model, and state where attribution or timing can distort the result. Read our calculation and editorial methodology.

Common questions

Frequently asked questions

What belongs in build cost?

Include product, design, engineering, security, testing, infrastructure, support, maintenance, and the management required to keep the system reliable.

How should opportunity cost be estimated?

Use the monthly cash benefit or avoided cost that is credibly delayed by the longer option, not the entire revenue touched by the system.

Does a cheaper option always win?

No. Control, strategic differentiation, compliance, data portability, vendor risk, and internal capability can outweigh modeled cost.

Why can break-even be unavailable?

If the option with the higher upfront cost does not have enough recurring savings, the cost gap never closes under the entered assumptions.

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