Construction Loan Calculator
Last updated: October 15, 2026
Estimate interest during construction and a projected permanent-loan payment.
Estimated construction interest
—
- Maximum loan amount: —
- Average drawn balance: —
- Projected permanent payment: —
On this page
Quick summary: Estimate interest during construction and a projected permanent-loan payment.
Read the complete guide
Updated reference sections in this guide are in English.
What this calculator estimates
Estimate interest during construction and a projected permanent-loan payment.
How to use it
Enter Total project cost ($); Cash contribution ($); Construction loan rate (%); Construction period (months); Average drawn balance (%); Permanent loan rate (%); Permanent term. Select Calculate to update the results.
How the calculation works
Loan principal = project cost minus the cash contribution. Estimated average drawn balance = principal × entered average-draw percentage. Construction interest = average drawn balance × annual rate/100 × construction months/12. The permanent payment amortizes the same principal at the permanent rate and term.
Worked example: starting scenario
| Total project cost ($) | 600000 |
|---|---|
| Cash contribution ($) | 120000 |
| Construction loan rate (%) | 8.5 |
| Construction period (months) | 12 |
| Average drawn balance (%) | 55 |
| Permanent loan rate (%) | 6.75 |
| Permanent term | 30 years |
| Estimated construction interest | $22,440.00 |
|---|---|
| Maximum loan amount | $480,000.00 |
| Average drawn balance | $264,000.00 |
| Projected permanent payment | $3,113.27 |
Important limitations
The average draw is an assumption rather than a dated draw schedule. Construction interest is reported separately and is not added to permanent principal. Origination fees, inspection charges, reserves, overruns and compounding during construction are excluded.