Construction Loan Calculator: Payment During Build
Work out the monthly payment and total interest on a construction loan — the short-term financing that pays the builder during the build, before being replaced or converted into a permanent mortgage.
Adjust the inputs and select Calculate for a full breakdown.
Year-by-year amortization schedule
Compare Common Scenarios
How the numbers shift across typical situations for this calculator:
| Scenario | Monthly payment | Total interest | Total of payments |
|---|---|---|---|
| $300k · 9% · 1-year | $26,235.44 | $14,825.32 | $314,825.32 |
| $150k · 10.5% · 1-year | $13,222.29 | $8,667.49 | $158,667.49 |
| $600k · 8.5% · 2-year | $27,273.40 | $54,561.72 | $654,561.72 |
| $80k · 11% · 1-year | $7,070.53 | $4,846.39 | $84,846.39 |
How This Calculator Works
Enter the construction loan amount, the APR, and the term. The calculator turns the rate into one constant monthly payment using the amortization formula and shows total interest across the term. Real-world construction loans are usually interest-only on drawn balances during the build — this model is a simplified upper bound for budgeting.
The Formula
Fixed-Rate Amortization
P = loan amount, r = monthly rate (APR ÷ 12), n = number of monthly payments
Worked Example
A $300,000 construction loan at 9% APR over 1 year amortized in full produces a monthly payment of about $26,235. Most builds run as interest-only during construction (interest only on the amount drawn so far), so actual monthly cash needed is much lower until completion.
Key Insight
Construction loans price higher than permanent mortgages because the lender is funding work-in-progress with no finished collateral. The simplest path is a construction-to-permanent loan that converts to a regular mortgage at completion, saving a second round of fees and underwriting. Compare the all-in cost — rate plus origination, plus appraisal, plus inspection draws — not just the headline APR.
Construction-to-permanent vs two-time-close
Two construction lending structures. (1) CONSTRUCTION-TO-PERMANENT ('C-to-P' or 'one-time close') — single closing combines construction loan + automatic conversion to permanent mortgage at completion. Saves second set of closing costs (~$3K-$8K). Permanent mortgage rate is locked at initial closing, which is risk-favorable if rates rise during construction; risk-unfavorable if rates fall.
(2) TWO-TIME-CLOSE — separate construction loan, then borrower obtains permanent mortgage at completion. Allows shopping for best permanent mortgage rate at completion. Risk: borrower must qualify again at completion; if income or credit declines during construction, may not qualify. Also adds second closing costs.
For most residential construction projects 2024, construction-to-permanent is the standard. The locked rate eliminates timing risk on the permanent mortgage portion. Custom-build buyers and developers more often use two-time-close to maintain flexibility, particularly when expecting interest rates to fall over construction period (1-2 years).
Why construction loan rates are higher
Construction loans typically carry 0.5-1.5% premium above permanent mortgage rates. The rate premium reflects elevated lender risk: (1) PROJECT COMPLETION RISK — construction projects can run over budget, fall behind schedule, or fail to complete. Lender's collateral (the building under construction) has limited value until completion. (2) DRAW MONITORING — lender must inspect work at each draw to verify progress, adding operational cost.
(3) BORROWER PERFORMANCE — construction draw schedule depends on borrower (or general contractor) performing per schedule. Delays cause holding period extensions and additional interest cost. (4) NO REVENUE STREAM DURING CONSTRUCTION — borrower must service interest from external income during construction; vacant lot has no income generation.
Strategies to reduce construction loan cost: (1) Larger down payment / equity (typical construction loan requires 20-25% equity; some programs accept less); (2) Selecting experienced GC with strong track record (reduces project completion risk perceived by lender); (3) Cost overrun buffer in budget (lenders include 5-10% contingency line; using none preserves flexibility for change orders); (4) Pre-qualifying for permanent mortgage early — even with C-to-P, demonstrating sustainable permanent financing capacity reduces lender risk.
U.S. construction loan typical terms (2024)
Reference construction loan terms for various project types. Permanent loan conversion follows project completion.
| Project type | Construction rate | Term length | Equity required |
|---|---|---|---|
| Single-family residential (C-to-P) | 7.5-8.5% | 12-18 months | 20-25% |
| Multifamily ground-up | 7.5-9.0% | 18-30 months | 20-30% |
| Commercial new construction | 7.0-9.0% | 18-36 months | 25-35% |
| Renovation / major remodel | 8.0-9.5% | 6-18 months | 25-35% |
| Owner-builder (self-built) | 8.5-10.0% | 12-18 months | 30-40% |
| FHA 203(k) renovation | Standard FHA + 0.5-1% | Standard FHA term | 3.5% |
| VA construction loan | Standard VA + 0.5-1% | Standard VA term | 0% |
Construction loans require approved plans, builder, and budget before underwriting. Construction-to-permanent structure (one-time close) is the residential standard; two-time-close more common for commercial projects with longer time horizons. Always include 10-15% contingency for unexpected cost overruns; lenders typically require 5-10% but more is prudent for first-time owner-builders.
Frequently Asked Questions
How is a construction loan different from a mortgage?
It funds the build itself, not the purchase of a finished home. Funds are drawn in stages as construction milestones are met, and most loans run interest-only during the build until full conversion or payoff.
Why are construction loan rates higher?
The lender is financing work-in-progress with no finished collateral and substantial completion risk. Rates typically price at prime plus 1 to 3 points, sometimes more for owner-builder projects.
What is construction-to-permanent financing?
A single loan that funds the build and converts to a regular mortgage at completion. It saves a second round of closing costs and underwriting compared to two separate loans.
What happens at completion?
Either you pay off the construction loan with a permanent mortgage you arrange separately, or it converts to a permanent mortgage if you used construction-to-permanent financing.
Do I make payments during the build?
Yes, but usually interest-only on the amount drawn so far. Cash needed grows as more of the loan is drawn, peaking right before completion when the full principal is outstanding.
When is this calculator unreliable?
When ignoring soft costs (architect/engineering 5-15% of construction cost; permits, plans, inspections add 3-5%; financing costs including closing 2-4%), when actual draws don't follow scheduled plan (slow draws save interest but extend timeline; rapid draws accelerate interest cost), or when conversion to permanent financing has cost or rate uncertainty (two-time-close exposes borrower to rate movement during construction).
References & Authoritative Sources
- Consumer Financial Protection Bureau (CFPB) — Construction Loan Disclosure Requirements · consulted June 1, 2026 · Federal regulator guidance on construction loans
- National Association of Home Builders (NAHB) — Construction Lending Survey · consulted June 1, 2026 · Industry data on U.S. construction lending
- U.S. Department of Housing and Urban Development (HUD) — FHA Construction Lending · consulted June 1, 2026 · FHA construction loan programs
Related Calculators
Data Sources & Benchmarks
This calculator draws on 1 independent, dated source. The starting values for interest rate are taken from the benchmarks below and refresh whenever the snapshots are updated.
Methodology & Review
Construction loan payment during the construction phase typically equals loan amount drawn × interest rate / 12 (interest-only on drawn amount). The calculator returns monthly interest payment during construction. Construction loans differ from permanent mortgages: typically 12-18 month term; interest-only during construction; conversion to permanent mortgage at completion; higher rates than permanent mortgages (~0.5-1.5% premium); draw schedule with inspections required at each draw. RELIABILITY: Reliable for construction-phase interest calculation. Less reliable for total project cost picture because construction loans involve (a) origination fees (1-2%), (b) inspection fees per draw ($150-$300 × 5-7 draws), (c) builder's risk insurance, (d) construction permit and other soft costs, and (e) conversion to permanent mortgage with separate origination at completion.
Updated