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Construction Loan Interest Calculator

Build a dated draw schedule and calculate interest only on principal actually outstanding. Add principal repayments, optional unused-commitment fees, current per-diem interest, and a full interval-by-interval audit table.

Your calculated results

The sample values calculate automatically. Change any input to evaluate your own scenario.

Construction loan agreements vary. Some lenders capitalize interest, charge inspection or draw fees, use monthly average balances, limit re-advances, or calculate unused-line fees differently. This page models simple daily interest on outstanding principal.

Draw-based interest

Measure the cost of money only while it is actually outstanding

A construction commitment may be large, but the entire commitment is usually not advanced on the first day. This calculator therefore divides the loan into date intervals and uses the outstanding balance that existed during each interval.

Interval interest = Outstanding principal × Annual rate × Days ÷ Basis

The same interval method is used for an optional unused-commitment fee, except the base is the undrawn amount instead of the outstanding principal.

Average outstanding balance

The calculator also computes a day-weighted average balance. That is useful for understanding how much of the commitment was actually in use during the period rather than looking only at the final balance.

Need a standard amortization schedule after construction?

When the construction phase converts into a permanent amortizing loan, use Amortization Pro to create the full principal-and-interest schedule.

Frequently asked questions

Why is construction-loan interest based on draws?

Many construction loans charge interest on principal actually advanced rather than the entire commitment from day one. Each draw changes the balance used for later daily interest.

How are dates handled?

The calculator accrues interest for the elapsed calendar days from one event date to the next. A draw or repayment changes the balance after interest for the preceding interval has been calculated.

What is the unused commitment fee?

If your agreement charges an annual fee on the undrawn portion of the commitment, enter that rate. The calculator estimates it daily using the same selected day-count basis.

Can I enter repayments as well as draws?

Yes. Principal repayments reduce the outstanding balance for later interest intervals. The calculator prevents a repayment from exceeding the balance then outstanding.