Strategic decision tool

Build vs. buy SaaS calculator

This tool is for teams evaluating a SaaS purchase or renewal who need to assess the feasibility and long-term total cost of ownership of building the capability in-house.

Adjust the parameters below to model your total cost of ownership and get a strategic recommendation.

Application being evaluated

4 mo away
How long do you expect this solution to remain in active use? Longer lifespans increase total SaaS spend and can shift buy economics.
3 yrs
1 yr5 yrs
Higher criticality increases required quality and resilience.
3 / 5
15
How much does this app need to be tailored to your specific business?
3 / 5
15
How differentiating is this app to your business?
3.0 - High Business Logic
1.05.0

Buy

$
$

Annual SaaS cost total: $100K

compounded over lifespan
%
one-time
$

Build

10%70% / 30%90%

Output tokens cost 3–5× more than input. Generation-heavy workloads increase token spend significantly.

Model stackcoeff 1.00 · 1.00× output
$139K3-yr est.
Higher appetite means faster AI-assisted build velocity.
3 / 5
15
Planned implementation window for proprietary build.
6 months
1 mo2 yrs
$300K/yr
$

Count · cost per engineer / year

$

Count · cost per rep / year

Comparison

Side-by-side 3-year TCO for vendor purchase vs proprietary build.

Vendor (Buy)
$463K

License, implementation, and support-linked SaaS spend.

Proprietary (Build)
$423K

Development, maintenance, and ongoing support costs.

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3-year savings
$40K
Recommended: Proprietary (Build)

Build estimate assumes 5× velocity via AI-assisted development.

Save scenario

Saves your inputs and produces a summary analysis. Add your email if you want a copy in your inbox.

Session ID: —

Common questions

Quick answers to the questions behind every build-or-buy software decision.

Should I build or buy my SaaS?

It depends on the total cost of ownership over the software’s lifespan, how differentiating the capability is, how fast you need it, and your team’s build velocity. Commodity needs usually favor buying vendor SaaS; differentiating, long-lived capabilities can favor building. The calculator above compares the TCO of both paths over your expected app lifespan (1–5 years) so you decide with numbers rather than instinct.

Should I vibe code my SaaS instead of buying it?

AI-assisted (“vibe”) coding can dramatically cut build time and cost, which shifts the build-vs-buy math toward building — especially for differentiated features. Model your AI model-stack costs and faster build velocity above, and the tool shows whether building still beats a vendor SaaS subscription over your chosen horizon.

How do I calculate total cost of ownership for build vs. buy?

Add up the full multi-year cost of each path. For buying: license, implementation, support, and annual price increases. For building: engineering and AI/model costs, time-to-live, ongoing maintenance, and support. This tool computes both over your chosen horizon (1–5 years) and recommends the cheaper, lower-risk option for your inputs.

When does building software cost less than buying SaaS?

Building tends to win when the app is highly differentiating, has a long lifespan, vendor SaaS pricing is high or rising fast, and your build velocity is strong (e.g. AI-assisted development). Buying tends to win for short-lived, commodity, or compliance-sensitive needs. Enter your numbers above to find the crossover point.