construction-loan-calculator

Professional construction loan calculator with interest-only build phase and construction-to-permanent mortgage. Model draw schedules, fees, points, and get payment, total interest, and cost breakdown with printable schedules.

Full original guide (expanded)

Authoritative Data Source & Methodology

AuthoritativeDataSource: CFPB — Construction Loans (Regulatory Consumer Guidance), updated periodically. Supplementary lender practices: Fannie Mae Single-Close Construction (seller guidance).
Tutti i calcoli si basano rigorosamente sulle formule e sui dati forniti da questa fonte.

The Formula Explained

Construction interest (monthly simple on drawn funds)

\[ I_{\text{build}} = \sum_{m=1}^{M} \Big( B_{m-1} + D_m \cdot \tfrac{1}{2} \Big)\cdot \frac{r_c}{12} \]

where \(B_{m-1}\) is balance before month \(m\), \(D_m\) the draw in month \(m\), \(M\) months, and \(r_c\) the construction APR (decimal). The half-month factor approximates average outstanding after a mid-month draw.

Permanent payment (amortized)

\[ P = L \cdot \frac{i(1+i)^N}{(1+i)^N - 1}, \quad i=\frac{r_p}{12},\; N=12\cdot Y \]

Glossary of Variables

  • Total Project Cost: Sum of hard and soft costs for the build.
  • Down Payment (%): Borrower equity paid up-front; loan amount = cost × (1 − %).
  • Construction APR: Interest rate applied to drawn funds during the build (interest-only).
  • Draw Pattern: Timing of disbursements (even/front/back loaded) that drives accrued interest.
  • Points & Fees: Up-front charges expressed as % of loan and/or dollars.
  • Permanent APR & Term: Rate and years used to compute the post-build mortgage payment.
  • Monthly Payment: Amortized mortgage payment after conversion.

How It Works: A Step-By-Step Example

Assume $400,000 total cost, 20% down (loan base $320,000), 10 months build at 8.5% APR, even draws, points 1% and $2,500 fees. Permanent APR 7.25% for 30 years.

  1. Loan Amount: \(L = 400{,}000 \times (1-0.20) = 320{,}000\).
  2. Draws: Even monthly (\(D_m = 32{,}000\)). Interest each month uses outstanding balance plus half the new draw.
  3. Build Interest: Sum monthly per formula; tool computes ≈ shown in the results.
  4. Points & Fees: \(0.01 \times 320{,}000 + 2{,}500 = 5{,}700\).
  5. Permanent Payment: Use amortization formula with \(r_p=7.25\%\), \(N=360\).

Frequently Asked Questions

Does this include interest reserves?

If your lender capitalizes interest, treat the reserve as part of project cost, which changes loan size and interest profile.

Can the permanent loan amount differ from the construction balance?

Yes. Some programs re-underwrite at completion or cap loan-to-value off the final appraisal.

What about variable construction rates?

This tool models a single APR. For floating rates, use a conservative scenario or re-run with alternative rates.

Are inspection fees per draw included?

Add them in “Fees ($)”. Per-draw costs can materially change all-in build-phase costs.

Can I change the draw dates?

Use front/back-loaded patterns to approximate timing. For exact dates, align with the builder’s schedule and re-estimate monthly interest.

Strumento sviluppato da Ugo Candido. Contenuti verificati da, CalcDomain Editorial Board.
Ultima revisione per l'accuratezza in data:

Audit: Complete
Formula (LaTeX) + variables + units
This section shows the formulas used by the calculator engine, plus variable definitions and units.
Formula (extracted LaTeX)
\[I_{\text{build}} = \sum_{m=1}^{M} \Big( B_{m-1} + D_m \cdot \tfrac{1}{2} \Big)\cdot \frac{r_c}{12}\]
I_{\text{build}} = \sum_{m=1}^{M} \Big( B_{m-1} + D_m \cdot \tfrac{1}{2} \Big)\cdot \frac{r_c}{12}
Formula (extracted LaTeX)
\[P = L \cdot \frac{i(1+i)^N}{(1+i)^N - 1}, \quad i=\frac{r_p}{12},\; N=12\cdot Y\]
P = L \cdot \frac{i(1+i)^N}{(1+i)^N - 1}, \quad i=\frac{r_p}{12},\; N=12\cdot Y
Formula (extracted text)
Construction interest (monthly simple on drawn funds) \[ I_{\text{build}} = \sum_{m=1}^{M} \Big( B_{m-1} + D_m \cdot \tfrac{1}{2} \Big)\cdot \frac{r_c}{12} \] where \(B_{m-1}\) is balance before month \(m\), \(D_m\) the draw in month \(m\), \(M\) months, and \(r_c\) the construction APR (decimal). The half-month factor approximates average outstanding after a mid-month draw. Permanent payment (amortized) \[ P = L \cdot \frac{i(1+i)^N}{(1+i)^N - 1}, \quad i=\frac{r_p}{12},\; N=12\cdot Y \]
Variables and units
  • P = principal (loan amount) (currency)
  • r = periodic interest rate (annual rate ÷ payments per year) (1)
  • n = total number of payments (years × payments per year) (count)
  • M = periodic payment for principal + interest (currency)
Sources (authoritative):
Changelog
Version: 0.1.0-draft
Last code update: 2026-01-19
0.1.0-draft · 2026-01-19
  • Initial audit spec draft generated from HTML extraction (review required).
  • Verify formulas match the calculator engine and convert any text-only formulas to LaTeX.
  • Confirm sources are authoritative and relevant to the calculator methodology.
Verified by Ugo Candido on 2026-01-19
Profile · LinkedIn

Authoritative Data Source & Methodology

AuthoritativeDataSource: CFPB — Construction Loans (Regulatory Consumer Guidance), updated periodically. Supplementary lender practices: Fannie Mae Single-Close Construction (seller guidance).
Tutti i calcoli si basano rigorosamente sulle formule e sui dati forniti da questa fonte.

The Formula Explained

Construction interest (monthly simple on drawn funds)

\[ I_{\text{build}} = \sum_{m=1}^{M} \Big( B_{m-1} + D_m \cdot \tfrac{1}{2} \Big)\cdot \frac{r_c}{12} \]

where \(B_{m-1}\) is balance before month \(m\), \(D_m\) the draw in month \(m\), \(M\) months, and \(r_c\) the construction APR (decimal). The half-month factor approximates average outstanding after a mid-month draw.

Permanent payment (amortized)

\[ P = L \cdot \frac{i(1+i)^N}{(1+i)^N - 1}, \quad i=\frac{r_p}{12},\; N=12\cdot Y \]

Glossary of Variables

  • Total Project Cost: Sum of hard and soft costs for the build.
  • Down Payment (%): Borrower equity paid up-front; loan amount = cost × (1 − %).
  • Construction APR: Interest rate applied to drawn funds during the build (interest-only).
  • Draw Pattern: Timing of disbursements (even/front/back loaded) that drives accrued interest.
  • Points & Fees: Up-front charges expressed as % of loan and/or dollars.
  • Permanent APR & Term: Rate and years used to compute the post-build mortgage payment.
  • Monthly Payment: Amortized mortgage payment after conversion.

How It Works: A Step-By-Step Example

Assume $400,000 total cost, 20% down (loan base $320,000), 10 months build at 8.5% APR, even draws, points 1% and $2,500 fees. Permanent APR 7.25% for 30 years.

  1. Loan Amount: \(L = 400{,}000 \times (1-0.20) = 320{,}000\).
  2. Draws: Even monthly (\(D_m = 32{,}000\)). Interest each month uses outstanding balance plus half the new draw.
  3. Build Interest: Sum monthly per formula; tool computes ≈ shown in the results.
  4. Points & Fees: \(0.01 \times 320{,}000 + 2{,}500 = 5{,}700\).
  5. Permanent Payment: Use amortization formula with \(r_p=7.25\%\), \(N=360\).

Frequently Asked Questions

Does this include interest reserves?

If your lender capitalizes interest, treat the reserve as part of project cost, which changes loan size and interest profile.

Can the permanent loan amount differ from the construction balance?

Yes. Some programs re-underwrite at completion or cap loan-to-value off the final appraisal.

What about variable construction rates?

This tool models a single APR. For floating rates, use a conservative scenario or re-run with alternative rates.

Are inspection fees per draw included?

Add them in “Fees ($)”. Per-draw costs can materially change all-in build-phase costs.

Can I change the draw dates?

Use front/back-loaded patterns to approximate timing. For exact dates, align with the builder’s schedule and re-estimate monthly interest.

Strumento sviluppato da Ugo Candido. Contenuti verificati da, CalcDomain Editorial Board.
Ultima revisione per l'accuratezza in data:

Audit: Complete
Formula (LaTeX) + variables + units
This section shows the formulas used by the calculator engine, plus variable definitions and units.
Formula (extracted LaTeX)
\[I_{\text{build}} = \sum_{m=1}^{M} \Big( B_{m-1} + D_m \cdot \tfrac{1}{2} \Big)\cdot \frac{r_c}{12}\]
I_{\text{build}} = \sum_{m=1}^{M} \Big( B_{m-1} + D_m \cdot \tfrac{1}{2} \Big)\cdot \frac{r_c}{12}
Formula (extracted LaTeX)
\[P = L \cdot \frac{i(1+i)^N}{(1+i)^N - 1}, \quad i=\frac{r_p}{12},\; N=12\cdot Y\]
P = L \cdot \frac{i(1+i)^N}{(1+i)^N - 1}, \quad i=\frac{r_p}{12},\; N=12\cdot Y
Formula (extracted text)
Construction interest (monthly simple on drawn funds) \[ I_{\text{build}} = \sum_{m=1}^{M} \Big( B_{m-1} + D_m \cdot \tfrac{1}{2} \Big)\cdot \frac{r_c}{12} \] where \(B_{m-1}\) is balance before month \(m\), \(D_m\) the draw in month \(m\), \(M\) months, and \(r_c\) the construction APR (decimal). The half-month factor approximates average outstanding after a mid-month draw. Permanent payment (amortized) \[ P = L \cdot \frac{i(1+i)^N}{(1+i)^N - 1}, \quad i=\frac{r_p}{12},\; N=12\cdot Y \]
Variables and units
  • P = principal (loan amount) (currency)
  • r = periodic interest rate (annual rate ÷ payments per year) (1)
  • n = total number of payments (years × payments per year) (count)
  • M = periodic payment for principal + interest (currency)
Sources (authoritative):
Changelog
Version: 0.1.0-draft
Last code update: 2026-01-19
0.1.0-draft · 2026-01-19
  • Initial audit spec draft generated from HTML extraction (review required).
  • Verify formulas match the calculator engine and convert any text-only formulas to LaTeX.
  • Confirm sources are authoritative and relevant to the calculator methodology.
Verified by Ugo Candido on 2026-01-19
Profile · LinkedIn

Authoritative Data Source & Methodology

AuthoritativeDataSource: CFPB — Construction Loans (Regulatory Consumer Guidance), updated periodically. Supplementary lender practices: Fannie Mae Single-Close Construction (seller guidance).
Tutti i calcoli si basano rigorosamente sulle formule e sui dati forniti da questa fonte.

The Formula Explained

Construction interest (monthly simple on drawn funds)

\[ I_{\text{build}} = \sum_{m=1}^{M} \Big( B_{m-1} + D_m \cdot \tfrac{1}{2} \Big)\cdot \frac{r_c}{12} \]

where \(B_{m-1}\) is balance before month \(m\), \(D_m\) the draw in month \(m\), \(M\) months, and \(r_c\) the construction APR (decimal). The half-month factor approximates average outstanding after a mid-month draw.

Permanent payment (amortized)

\[ P = L \cdot \frac{i(1+i)^N}{(1+i)^N - 1}, \quad i=\frac{r_p}{12},\; N=12\cdot Y \]

Glossary of Variables

  • Total Project Cost: Sum of hard and soft costs for the build.
  • Down Payment (%): Borrower equity paid up-front; loan amount = cost × (1 − %).
  • Construction APR: Interest rate applied to drawn funds during the build (interest-only).
  • Draw Pattern: Timing of disbursements (even/front/back loaded) that drives accrued interest.
  • Points & Fees: Up-front charges expressed as % of loan and/or dollars.
  • Permanent APR & Term: Rate and years used to compute the post-build mortgage payment.
  • Monthly Payment: Amortized mortgage payment after conversion.

How It Works: A Step-By-Step Example

Assume $400,000 total cost, 20% down (loan base $320,000), 10 months build at 8.5% APR, even draws, points 1% and $2,500 fees. Permanent APR 7.25% for 30 years.

  1. Loan Amount: \(L = 400{,}000 \times (1-0.20) = 320{,}000\).
  2. Draws: Even monthly (\(D_m = 32{,}000\)). Interest each month uses outstanding balance plus half the new draw.
  3. Build Interest: Sum monthly per formula; tool computes ≈ shown in the results.
  4. Points & Fees: \(0.01 \times 320{,}000 + 2{,}500 = 5{,}700\).
  5. Permanent Payment: Use amortization formula with \(r_p=7.25\%\), \(N=360\).

Frequently Asked Questions

Does this include interest reserves?

If your lender capitalizes interest, treat the reserve as part of project cost, which changes loan size and interest profile.

Can the permanent loan amount differ from the construction balance?

Yes. Some programs re-underwrite at completion or cap loan-to-value off the final appraisal.

What about variable construction rates?

This tool models a single APR. For floating rates, use a conservative scenario or re-run with alternative rates.

Are inspection fees per draw included?

Add them in “Fees ($)”. Per-draw costs can materially change all-in build-phase costs.

Can I change the draw dates?

Use front/back-loaded patterns to approximate timing. For exact dates, align with the builder’s schedule and re-estimate monthly interest.

Strumento sviluppato da Ugo Candido. Contenuti verificati da, CalcDomain Editorial Board.
Ultima revisione per l'accuratezza in data:

Audit: Complete
Formula (LaTeX) + variables + units
This section shows the formulas used by the calculator engine, plus variable definitions and units.
Formula (extracted LaTeX)
\[I_{\text{build}} = \sum_{m=1}^{M} \Big( B_{m-1} + D_m \cdot \tfrac{1}{2} \Big)\cdot \frac{r_c}{12}\]
I_{\text{build}} = \sum_{m=1}^{M} \Big( B_{m-1} + D_m \cdot \tfrac{1}{2} \Big)\cdot \frac{r_c}{12}
Formula (extracted LaTeX)
\[P = L \cdot \frac{i(1+i)^N}{(1+i)^N - 1}, \quad i=\frac{r_p}{12},\; N=12\cdot Y\]
P = L \cdot \frac{i(1+i)^N}{(1+i)^N - 1}, \quad i=\frac{r_p}{12},\; N=12\cdot Y
Formula (extracted text)
Construction interest (monthly simple on drawn funds) \[ I_{\text{build}} = \sum_{m=1}^{M} \Big( B_{m-1} + D_m \cdot \tfrac{1}{2} \Big)\cdot \frac{r_c}{12} \] where \(B_{m-1}\) is balance before month \(m\), \(D_m\) the draw in month \(m\), \(M\) months, and \(r_c\) the construction APR (decimal). The half-month factor approximates average outstanding after a mid-month draw. Permanent payment (amortized) \[ P = L \cdot \frac{i(1+i)^N}{(1+i)^N - 1}, \quad i=\frac{r_p}{12},\; N=12\cdot Y \]
Variables and units
  • P = principal (loan amount) (currency)
  • r = periodic interest rate (annual rate ÷ payments per year) (1)
  • n = total number of payments (years × payments per year) (count)
  • M = periodic payment for principal + interest (currency)
Sources (authoritative):
Changelog
Version: 0.1.0-draft
Last code update: 2026-01-19
0.1.0-draft · 2026-01-19
  • Initial audit spec draft generated from HTML extraction (review required).
  • Verify formulas match the calculator engine and convert any text-only formulas to LaTeX.
  • Confirm sources are authoritative and relevant to the calculator methodology.
Verified by Ugo Candido on 2026-01-19
Profile · LinkedIn
Formulas

(Formulas preserved from original page content, if present.)

Version 0.1.0-draft
Citations

Add authoritative sources relevant to this calculator (standards bodies, manuals, official docs).

Changelog
  • 0.1.0-draft — 2026-01-19: Initial draft (review required).