Rex says
Money math without the spreadsheet headache. Plug in your numbers and I'll show you exactly where the dollars land.
Try a scenario
Click to load — tweak from there.Inputs
Result
Build cost minus buy cost
$165,250
Lower all-in cost
Buying existing
All-in cost to buy existing
$472,750
All-in cost to build new
$638,000
Carrying cost during construction
$26,000
Build cost per sq ft (all-in)
$290
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One click, a permanent link with your numbers baked in.
How to use this
- 1Enter existing home purchase price ($).
- 2Enter closing costs (%).
- 3Enter immediate repairs and updates ($).
- 4Enter land cost ($).
- 5Enter new home size (sq ft).
- 6Enter construction cost ($/sq ft).
- 7Enter site work, well, septic, driveway ($).
- 8Enter plans, permits, impact fees ($).
- 9Enter build duration (months).
- 10Enter monthly carrying cost during build ($).
- 11Read your build cost minus buy cost on the right — it updates as you type.
- 12Hit Share to keep the scenario or send it to someone.
About this calculator
Buying an existing home and building new rarely compare cleanly, because the costs sit in different places. Buying carries a purchase price, closing costs, and a repair-and-update bill that most buyers underestimate in the first two years. Building carries land, site work, hard construction cost per square foot, soft costs like permits, plans, and impact fees, plus months of carrying two housing payments — construction loan interest on one side and rent or an existing mortgage on the other. This calculator puts both paths on a single all-in number, including that carrying period, so you can see the real gap rather than comparing a listing price to a builder's base price per square foot. 2026 US national build costs commonly run $160-$280 per square foot for the structure alone, before land.
Worked example
Using the values the calculator loads with:
Inputs
- Existing home purchase price: 425000 $
- Closing costs: 3 %
- Immediate repairs and updates: 35000 $
- Land cost: 110000 $
- New home size: 2200 sq ft
- Construction cost: 195 $/sq ft
- Site work, well, septic, driveway: 45000 $
- Plans, permits, impact fees: 28000 $
- Build duration: 10 months
- Monthly carrying cost during build: 2600 $
Results
- Build cost minus buy cost: $165,250
- Lower all-in cost: Buying existing
- All-in cost to buy existing: $472,750
- All-in cost to build new: $638,000
- Carrying cost during construction: $26,000
- Build cost per sq ft (all-in): $290
What each field means
Inputs
- Existing home purchase price ($)
- The existing home purchase price used in the calculation, measured in $. Starts at 425000 $ so you have a working example on load. Accepted range: 20000–5000000 $.
- Closing costs (%)
- The closing costs used in the calculation, measured in %. Starts at 3 % so you have a working example on load. Accepted range: 0–8 %.
- Immediate repairs and updates ($)
- The immediate repairs and updates used in the calculation, measured in $. Starts at 35000 $ so you have a working example on load. Accepted range: 0–500000 $.
- Land cost ($)
- The land cost used in the calculation, measured in $. Starts at 110000 $ so you have a working example on load. Accepted range: 0–3000000 $.
- New home size (sq ft)
- The new home size used in the calculation, measured in sq ft. Starts at 2200 sq ft so you have a working example on load. Accepted range: 400–12000 sq ft.
- Construction cost ($/sq ft)
- The construction cost used in the calculation, measured in $/sq ft. Starts at 195 $/sq ft so you have a working example on load. Accepted range: 80–600 $/sq ft.
- Site work, well, septic, driveway ($)
- The site work, well, septic, driveway used in the calculation, measured in $. Starts at 45000 $ so you have a working example on load. Accepted range: 0–500000 $.
- Plans, permits, impact fees ($)
- The plans, permits, impact fees used in the calculation, measured in $. Starts at 28000 $ so you have a working example on load. Accepted range: 0–300000 $.
- Build duration (months)
- The build duration used in the calculation, measured in months. Starts at 10 months so you have a working example on load. Accepted range: 3–36 months.
- Monthly carrying cost during build ($)
- The monthly carrying cost during build used in the calculation, measured in $. Starts at 2600 $ so you have a working example on load. Accepted range: 0–20000 $.
Results
- Build cost minus buy cost
- Returned as a money amount in US dollars and shown as the headline result. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Lower all-in cost
- Returned as a plain value. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- All-in cost to buy existing
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- All-in cost to build new
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Carrying cost during construction
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Build cost per sq ft (all-in)
- Returned as a money amount in US dollars. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
FAQ
Is it cheaper to buy or build in 2026?
In most US metros buying existing is still cheaper per square foot, because existing homes were built at lower material and labor costs. Building wins more often in rural areas with inexpensive land, and whenever the existing inventory needs a gut renovation anyway.
What do people forget when budgeting a build?
Site work and soft costs. A builder's per-square-foot number usually covers the structure, not the well, septic, driveway, grading, utility hookups, permits, or impact fees — those routinely add $50,000 or more.
Why include carrying cost?
You pay for housing during construction. Ten months of rent or an existing mortgage plus construction loan interest is real money that never shows up in a builder's quote, and it is often the single largest hidden line in the comparison.
Accuracy and limitations
- Results are estimates before tax, fees, and inflation unless an input explicitly covers them.
- Rates are treated as fixed for the whole period — variable-rate products will drift from this projection.
- This is educational maths, not financial advice. Check anything contractual with the lender or your accountant.
Related tools
Cite this calculator
Writing about this topic? Grab a citation — every link helps keep these tools free.
RevenueLab. (2026). Buy vs Build a House Cost Calculator. Retrieved from https://www.revenuelab.fyi/toolbox/buy-vs-build-house-cost
<p>Source: <a href="https://www.revenuelab.fyi/toolbox/buy-vs-build-house-cost" target="_blank" rel="noopener">Buy vs Build a House Cost Calculator — RevenueLab</a> (2026).</p>
Source: [Buy vs Build a House Cost Calculator — RevenueLab](https://www.revenuelab.fyi/toolbox/buy-vs-build-house-cost) (2026).