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Loan Calculator

Calculate fixed-rate loan payments, total interest, amortization, and extra-principal savings. Enter principal, annual note rate, and term; fees are excluded.

Use this result well

Inputs that matter
Principal, annual note rate, monthly term, optional extra principal, and optional gross income plus other recurring monthly debt
Output to expect
Fixed monthly payment, total interest and payments, payoff date, amortization schedule, extra-payment savings, term comparison, and a simplified debt-to-income planning ratio
How it works
Standard fixed-rate amortization with a zero-interest branch and balance-capped extra principal; each row recalculates interest on the remaining balance
  • The entered rate excludes fees and is not a fee-inclusive APR; compare the lender disclosure, fees, prepayment rules, and actual payment timing.
  • For the DTI planning ratio, include all recurring monthly debt and verify the lender’s own income and debt definitions.

Choose your path

Built around the job you need to finish

Compare fixed-payment loan cost, payoff timing, and extra-payment effects without confusing interest rate, APR, or affordability.

Borrower comparing offers

Compare the payment and total interest for the same principal across rates and terms.

Enter principal/rate/term, inspect formula and totals, then compare standard terms one assumption at a time.

Can compare like-for-like loan scenarios and knows the estimate excludes lender fees unless modeled.

Existing borrower

Estimate how a recurring extra payment changes payoff time and interest.

Add a monthly extra amount and review the complete amortization and savings comparison.

Sees a payoff that never overpays principal and can verify the last scheduled balance reaches zero.

Mobile budget planner

Check whether the payment fits monthly cash flow without treating a quick ratio as approval.

Enter monthly income, read payment and ratio context, and review the result on a narrow screen.

Completes the flow with named 44px controls and treats affordability as planning context, not underwriting.

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Projects using Loan Calculator

This tool is part of these guided projects. Each project provides step-by-step instructions with checklists and all the tools you need in one place.

Buy a Home

Coordinate a home-purchase decision from actual cash flow, official credit and loan documents, inspected property evidence, written contracts, and closing controls.

7 steps4 toolsStart project

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Reference & details

How it works

Monthly Payment

P is principal, r is annual note rate percent divided by 100 and 12, and n is the exact number of monthly payments. At zero interest, the scheduled payment is P/n. No whole-year rounding is applied.

M = P[r(1+r)^n]/[(1+r)^n-1]

Modeled Payments and Interest

Sum the schedule's actual payments, including any extra principal and the smaller final payoff. Interest is this total minus principal. Display and CSV amounts round to cents; calculations retain precision. Fees and prepayment penalties are not included.

Modeled interest = Sum of actual payments − Principal

Amortization Schedule

Each payment splits into interest and principal. Interest depends on the opening balance and monthly note rate; it need not exceed principal in early payments. The schedule starts next month, not on a lender-confirmed payment date.

Interest = Balance × (Annual note rate percent ÷ 100 ÷ 12); Principal = Payment − Interest

Updated: August 2026

Example Scenarios

Illustrative fixed-rate scenario, excluding fees and extra payments; not a current rate offer.

Principal: $25,000Rate: 4.5%Term: 5 years

→ $466.08/month; $2,964.53 modeled interest

Illustrative fixed-rate principal-and-interest comparison, excluding fees and extra payments.

Principal: $10,000Rate: 8%Term: 3 years

→ $313.36/month; $1,281.09 modeled interest

Illustrative level-payment loan only. Student-loan subsidies, income-based plans, deferment and forgiveness are not modeled.

Principal: $35,000Rate: 5.5%Term: 10 years

→ $379.84/month; $10,581.04 modeled interest

Common Mistakes to Avoid

Not checking APR vs interest rate

The annual note rate drives this payment model. APR is a broader annualized borrowing-cost measure that includes certain fees; do not substitute it for the note rate here. Review lender disclosures and fees separately.

Choosing the longest term for the lowest payment

For the same principal and positive fixed rate with no extra payments, a longer term reduces the scheduled payment and increases modeled interest. At zero interest, term length does not add interest. Compare the exact month count and fees separately.

FAQ

M = P[r(1+r)^n] / [(1+r)^n − 1], where P is principal, r is annual note rate percent ÷ 100 ÷ 12, and n is the exact whole-month term. At zero interest, M = P/n. This estimates fixed principal and interest only.

The note rate measures interest on the principal. APR includes certain fees and is a broader annualized cost measure. This calculator uses the note rate and does not calculate APR. Compare lender disclosures, fees and repayment assumptions as well as the stated rates.

For $25,000 at a fixed 4.5% with no fees or extra payments, 60 months gives a $466.08 scheduled payment and $2,964.53 modeled interest; 84 months gives $347.50 and $4,190.34. The longer term adds $1,225.81 in modeled interest.

Yes. Open the amortization schedule to inspect each month's principal, interest, extra principal and remaining balance. The split depends on rate and term. The final payment is capped at the remaining principal and accrued monthly interest.

No. The rate stays fixed throughout each scenario. Rate resets, variable-rate caps, fees, taxes, insurance and lender-specific rules are excluded. Optional household ratios show required debt separately from planned extra payments; they are not an approval decision or a complete affordability assessment.

About Loan Calculator

Estimate a fully amortizing fixed-rate loan in whole months, with optional extra principal payments. Enter the annual note rate, not APR. Fees, variable rates, lender-specific dates and program rules are excluded; results are planning estimates, not a quote or approval.