About Construction Loan Calculator Pro
Construction Loan Calculator Pro is a free set of construction loan calculators. You do not need an account, and we do not ask for your name, email or phone number to use them. The site is run by William ZZ and is not a lender or broker.
Last updated: November 13, 2026
Who runs this site
William ZZ
Founder & General Manager
William builds and maintains the calculators and pages on this site. Questions, bug reports and corrections go to support@constructionloancalculator.pro.
Why I built this tool
A construction loan does not behave like a mortgage. The lender releases the money in draws as the build progresses, and during construction you usually pay interest only on what has been drawn so far. When the house is finished, the balance converts to a permanent mortgage or is paid off with a new one.
Ordinary mortgage calculators assume the full loan from day one. For a construction loan that overstates the payments during the build, and it says nothing about the draw schedule or what happens at conversion. Those are the numbers people building a home need to budget for.
I built Construction Loan Calculator Pro to answer those questions in one place: what interest you will pay month by month while the house is built, what the permanent payment will be afterwards, and what the whole project costs. Every calculator is free, and the pages explain the formulas and assumptions behind the results, so you can check them instead of taking them on trust.
What the calculators do
- Construction Loan Calculator
Construction-phase interest, the permanent loan payment and the total cost from one set of inputs.
- Interest-Only Construction Loan Calculator
Month-by-month interest on the amount drawn so far, for equal or front-loaded draws.
- Land and Construction Loan Calculator
How land you own or buy counts toward the down payment and loan-to-cost.
- Permanent Loan Calculator
The mortgage payment after the build, when the construction loan converts or is refinanced.
- Construction Cost Estimator
A rough build budget from square footage and cost per square foot, to feed into the loan calculators.
How the numbers are calculated
- Calculator inputs are processed in your browser. Share links include the values you entered in the URL. This site also loads analytics and advertising services; see our Privacy Policy.
- Construction Loan Calculator (home page): each draw is released at the beginning of the month, interest is charged monthly on the balance drawn so far and paid during the build, so it is not added to the permanent loan.
- Interest-Only Construction Loan Calculator: monthly draws arrive mid-month; an optional draw at closing earns a full month of interest from month 1.
- Permanent Loan Calculator: construction interest is estimated on half the loan balance on average, added to the permanent principal, and then amortized with the standard fixed-rate formula.
- Default values on each page are assumed examples, not offers or quotes. Replace them with the numbers from your lender.
Worked example: checking the home calculator
An illustrative calculation, run on November 13, 2026 with the home page calculator’s default inputs. Enter the same numbers in the construction loan calculator to reproduce it.
| Item | Value |
|---|---|
| Project cost / your contribution | $500,000 / $100,000 |
| Construction loan | $400,000, 8% annual rate, 12 equal draws of about $33,333 |
| Interest in month 1 | $33,333.33 × 8% ÷ 12 = $222.22 |
| Interest in month 12 | $400,000 × 8% ÷ 12 = $2,666.67 |
| Total construction interest | $17,333.33 |
| Permanent loan payment | $400,000 at 6.5% for 30 years = $2,528.27 per month |
Total construction interest is the sum of the 12 monthly amounts, each rounded to the cent. The permanent payment uses the standard fixed-rate formula M = P × r ÷ (1 − (1 + r)−n), with P = $400,000, r = 6.5% ÷ 12 and n = 360. Calculator version as of November 13, 2026. Fees, taxes, insurance, daily interest accrual and lender-specific draw rules are not included.
Data sources
Rate and program pages cite public sources, including:
- Freddie Mac Primary Mortgage Market Survey (PMMS): weekly 30-year and 15-year mortgage rate benchmarks
- FRED: Bank Prime Loan Rate (DPRIME): the prime rate many construction loans are priced from
- FRED: Secured Overnight Financing Rate (SOFR): the other common index for variable-rate construction loans
- Fannie Mae Selling Guide B5-3.1-02: single-close construction-to-permanent rules
- U.S. Department of Housing and Urban Development (HUD): FHA program rules
What this site is not
We do not make loans, take applications, quote rates or give personal financial advice. Results are estimates for planning. Your actual rate, fees and payments come from your lender.
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