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Home Loan APR Calculator with Extra Payments

This calculator models monthly-compounding mortgage amortization and allows recurring monthly extra payments plus a one-time upfront extra payment. It also produces an estimated annual percentage rate (APR) that annualizes total finance charges (interest plus specified upfront fees) across the borrower's payoff period.

The APR estimate is provided for comparison and planning. Regulatory APR disclosures follow specific rules and rounding; this tool provides an approximate, transparent calculation you can use to explore scenarios and how extra payments reduce cost and time.

Updated Nov 13, 2025

Calculates scheduled monthly payment, adjusted effective payment with recurring extra amounts, estimated payoff time and totals.

Inputs

Results

Updates as you type

Scheduled monthly payment

$1,432.25

Effective monthly payment (with recurring extra)

$1,432.25

Estimated payoff time

—

Total paid (including fees and one-time extra)

—

Estimated interest paid

—

OutputValueUnit
Scheduled monthly payment$1,432.25USD
Effective monthly payment (with recurring extra)$1,432.25USD
Estimated payoff time—months
Total paid (including fees and one-time extra)—USD
Estimated interest paid—USD
Primary result$1,432.25

Visualization

Methodology

Amortization uses the standard fixed-rate loan formula with monthly compounding: scheduled payment = P * (r*(1+r)^n) / ((1+r)^n - 1), where r is the monthly interest rate and n is the total months. Recurring extra payments are added to the scheduled payment and the payoff time is derived from the closed-form logarithmic solution when extra payment exceeds monthly interest.

The APR shown is an annualized estimate computed as: (total finance charge) / principal / years_to_payoff * 100. Total finance charge = interest paid over the estimated payoff period plus the upfront fees you enter. This estimate is intended for scenario comparison rather than as a replacement for a formal Truth in Lending APR calculation.

Worked examples

Example: $300,000 principal, 4.0% annual rate, 30 years, $200 extra monthly reduces payoff months and total interest. APR estimate will fall because finance charge falls as interest decreases.

If extra monthly ≤ monthly interest portion, the loan will not amortize; the tool reports a safeguard large payoff_months value and warns you to increase payment.

Key takeaways

This tool helps compare how extra payments and fees affect loan payoff time, total interest, and an estimated annualized cost. Use values here for planning and scenario comparison.

For legally binding APR figures and exact disclosures, use lender-provided documents or consult a qualified financial professional.

Further resources

External guidance

Expert Q&A

Is the APR returned here the legally required APR?

No. The APR in this tool is an annualized estimate for comparison and planning. Legal APR disclosures follow prescribed regulatory methods and rounding. For official APRs refer to lender disclosures or consult a qualified advisor.

Do extra payments always reduce the APR?

Extra payments reduce the amount of interest paid by shortening the period the principal is outstanding. The estimated APR (annualized finance charge) typically decreases as interest paid falls, but results depend on size and timing of fees and extras.

What if my effective payment is too small to cover monthly interest?

If effective_payment is less than or equal to the monthly interest portion (principal * monthly_rate), the calculator will report an infeasibly large payoff period. Increase payments or contact the lender.

How accurate are these numbers?

Calculations use standard closed-form formulas and common numerical functions. The APR is an approximation that annualizes finance charges; it does not substitute for lender-provided Truth in Lending disclosures. See citations for standards on numerical accuracy and financial measurement.

Sources & citations