Compare in-house build costs with vendor setup and subscription spend across a planning horizon, including yearly cumulative totals. Use it to test different inputs quickly, compare outcomes, and understand the main factors behind the result before moving on to related tools or deeper guidance.
Last updated
What this planner compares Use it to compare one-time build spend plus ongoing support against vendor setup and subscription costs over a defined horizon.
Currency display
Switch the presentation currency for the totals and yearly comparison sheet.
Cost planning result
Building in-house stays cheaper
The cheaper path is ahead by $75,000.00 over 5 years.
Total build cost
$350,000.00
Total buy cost
$425,000.00
Annual build average
$70,000.00
Annual buy average
$85,000.00
Build-vs-buy comparison sheet
Year
Build cumulative
Buy cumulative
Cheaper path
Gap
1
$230,000.00
$105,000.00
Buy
$125,000.00
2
$260,000.00
$185,000.00
Buy
$75,000.00
3
$290,000.00
$265,000.00
Buy
$25,000.00
4
$320,000.00
$345,000.00
Build
$25,000.00
5
$350,000.00
$425,000.00
Build
$75,000.00
Planning note Build first becomes the cheaper cumulative path in year 4.
Build vs buy calculator: compare in-house development costs with vendor spend over time
A build vs buy calculator compares the full cost of building a solution internally with the cumulative cost of buying and running a vendor product over a chosen planning horizon, so you can see not just the headline total but when one path becomes cheaper than the other.
What this build-vs-buy comparison includes
The calculator treats the build path as a one-time development investment plus recurring annual maintenance, and the buy path as a one-time setup or implementation cost plus recurring annual license spend. That gives you a cleaner total-cost-of-ownership comparison than checking only the first-year budget line.
The decision still is not purely financial. Build can offer more control and customisation, while buy can reduce delivery time and vendor-management overhead. The calculator is most useful when you want the cost side stated clearly before layering in strategic considerations.
The yearly comparison table shows how the cumulative build cost and cumulative buy cost change year by year. That matters because a path that looks expensive in year one can become cheaper later, or a path that looks attractive initially can become more expensive once recurring vendor spend compounds.
The first cheaper year is especially useful in planning. If buy stays cheaper for the whole horizon, that suggests the vendor path is financially lighter under the current assumptions. If build becomes cheaper after a few years, the decision may depend on whether the organisation expects to use the solution long enough to realise that payback.
Worked example: expensive build, lower recurring vendor costs
Suppose an internal build costs 200,000 upfront and 30,000 a year to maintain, while a vendor requires 25,000 to implement and 80,000 a year in license fees. Over 5 years, build totals 350,000 and buy totals 425,000, so build ends up cheaper by 75,000.
That does not automatically mean you should build. It means the cost case for building is stronger across that horizon. If the team lacks delivery capacity, the strategic answer could still be to buy even when the pure cost sheet favours building.
Limits of a build-vs-buy calculator
This planner does not model delivery risk, scope creep, implementation delays, security requirements, integration complexity, exit costs, or productivity impact. Those factors can change the real answer materially, especially for enterprise software and operational platforms.
Use the result as a decision-support worksheet, not as an automatic verdict. A strong build-vs-buy decision usually combines cost, control, time-to-value, risk, internal capability, and long-term dependency analysis.
Further reading
Wikipedia — Opportunity cost — Useful framing for the trade-off between internal development effort and alternative uses of time and capital.
Frequently asked questions
What costs should I include on the build side?
Include the realistic one-time development cost and the recurring annual cost to maintain, improve, secure, and support the system. If the internal team will keep working on it after launch, that ongoing cost belongs in the build column.
What costs should I include on the buy side?
Include one-time implementation, migration, onboarding, or setup charges plus the recurring vendor subscription, support, or license spend. If a vendor price rises over time, use a conservative recurring number rather than the lowest promotional price.
Does the cheaper option automatically mean the better decision?
No. Cost is only one part of the decision. Time-to-value, control, compliance, integration effort, security, vendor lock-in, and internal delivery risk can outweigh a pure cost advantage.
When does building usually make more financial sense?
Building tends to look better when the upfront investment is manageable, the recurring vendor cost is high, and the organisation expects to use the solution for long enough to spread the build cost over many years.
