Build vs. buy calculator

Compare complete scenarios, not two headline prices

"Building costs less per square foot" and "buying is more expensive" can both be true and still lead to the wrong decision, because neither headline number includes everything the other path requires. This calculator lines up full totals on both sides.

Who should use this calculator

Use it once you have at least rough figures for both paths — a builder's cost breakdown and a comparable existing home's asking price — and want the full-cost comparison side by side, not just the construction total from the Construction Budget Calculator alone.

What each input means

• Build: land, hard costs, site/utilities, soft costs, contingency, monthly carry, and months — the same itemized construction plan as the Construction Budget calculator.
• Buy: purchase price, closing costs, immediate repairs, and moving cost — the full cash cost of buying a comparable existing home instead.

How the calculation works

The build side includes land, hard construction, site and utilities, soft costs, contingency, and carrying costs over time. The purchase side includes purchase price, closing costs, immediate repairs, and moving. The result subtracts the purchase total from the build total; it is a cost difference under your assumptions, not a recommendation.

A worked example, using the figures already loaded above

With the default build plan — $150,000 land, $350,000 hard costs, $60,000 site/utilities, 15% soft costs, 12% contingency, and 14 months at $3,500 monthly carry — the build total is about $727,080. Against a default purchase of $600,000 plus $15,000 closing, $10,000 in repairs, and $4,000 in moving costs — a buy total of $629,000 — building costs about $98,080 more under these assumptions.

How to interpret the result

A positive difference means building costs more in dollars under your inputs; it says nothing about the difference in what you get — a new, customized home versus an existing one, or a purchase that may need renovation the "buy" side's repair figure has not fully captured. Weigh the dollar difference against how much the non-financial factors matter to you.

What this calculator does not include

• The personal value of customization, location, disruption, or schedule risk.
• Financing differences between a construction loan and a standard mortgage.
• Any local builder bid — every build-side figure is a planning assumption.

Why the result is an estimate

Both totals are arithmetic on the numbers you entered. A build that appears cheaper on construction price alone can become more expensive after land and time costs; a purchase that appears more expensive may still require major repairs or renovation. The calculator makes those assumptions visible so a user can replace estimates with actual proposals.

Common mistakes to avoid

• Comparing a builder's verbal estimate against a listed asking price instead of two fully itemized totals.
• Using an optimistic build timeline when delays are common — test a delayed schedule as a second scenario.
• Comparing homes of different size, quality, or location and attributing the whole price gap to "build vs. buy."

Run more than one scenario

• Use an expected build schedule and a delayed schedule.
• Test a lower and higher contingency.
• Include comparable size, quality, land, location, and completed features.
• Use actual lender, builder, inspection, and closing figures as they arrive.

Related guides and calculators

• Construction Budget Calculator — a more careful review of the build side alone.
• Build-cost assumptions guide — document the unknowns behind each build-side figure.
• Cash to Close Calculator — a more detailed cash plan for the buy side.