Loan & mortgage repayment calculator: Comparing monthly loan repayments — Worked Scenario

What this scenario actually checks

Choose how to repay a loan or mortgage and compare the monthly burden. Equal monthly payments keep the total steady; equal principal payments decline at a positive rate; interest-only payments leave the principal for maturity. Inspect principal, interest and remaining debt for every month.

This walkthrough focuses on comparing monthly loan repayments. It follows the published tool inputs, not a new formula or an automatically verified legal, financial, medical or engineering determination.

Start by preparing the right inputs

Choose Equal monthly payments, Equal principal payments, or Interest monthly with principal at maturity. The summary separates first-month principal and interest. Review the monthly repayment table in groups of 12 and download every row as CSV. Enter the borrowed principal, nominal annual interest rate (%) and a whole number of years. For a mortgage, subtract the down payment from the property price first.

Before copying the example, confirm that each entered unit, date, dimension and default matches your real task. Changing only a visible number without revisiting its assumptions can change what the answer means.

• Choose Equal monthly payments, Equal principal payments, or Interest monthly with principal at maturity. The summary separates first-month principal and interest. Review the monthly repayment table in groups of 12 and download every row as CSV.
• Enter the borrowed principal, nominal annual interest rate (%) and a whole number of years. For a mortgage, subtract the down payment from the property price first.
• Monthly rate r = annual percentage / 1200; n = years × 12. Equal payment M = P × r / (1 − (1+r)^(-n)), or P/n at zero rate. Equal principal repays P/n plus opening balance × r each month. Interest-only pays P × r monthly and adds all P to the final payment.

Worked example with the calculator

Use the following input values: Principal 12,000; rate 0%; term 1 year.

The example output is Monthly payment 1,000.00. Twelve equal payments repay the principal without interest.

For comparison, the same tool also documents these inputs: Principal 100,000; rate 6%; term 30 years. Its result is Monthly payment 599.55. The monthly rate is 0.5% for 360 payments. The displayed payment is rounded, while total interest uses the unrounded amount.

What can change the answer

Monthly rate r = annual percentage / 1200; n = years × 12. Equal payment M = P × r / (1 − (1+r)^(-n)), or P/n at zero rate. Equal principal repays P/n plus opening balance × r each month. Interest-only pays P × r monthly and adds all P to the final payment. Total repayment is the sum of monthly payments; total interest is the sum of monthly interest. Each payment equals its principal and interest portions. Figures display two decimals, but calculations use unrounded values; displayed rows and lender rounding may differ. Principal must be positive and at most 1,000,000,000,000,000; rate 0–1,000%; term 1–100 whole years. Every monetary value uses the currency you entered; there is no currency conversion. Model reviewed 2026-10-21. Jurisdiction-neutral fixed-rate monthly, end-of-month payments. Excludes fees, points, insurance, taxes, regulatory APR, daily accrual, variable rates, grace periods and early repayment. Principal: positive up to 10^15; rate: 0–1000%; term: 1–100 whole years. A lender quote can differ.

Is nominal interest the same as APR? Not necessarily. APR may include lender fees and other charges under local rules. This model uses only the nominal interest rate and does not calculate regulatory APR.

Which repayment method has the smallest payment? At a positive rate, equal-principal payments start higher and decline; equal monthly payments stay steady. Interest-only starts with just interest but leaves all principal due at maturity. Compare total interest and the final payment too.

Before using the result for a real decision

For comparing monthly loan repayments, check the original measurements and input units, and save the assumptions alongside any number you share.

Where legal rules, official allowances, equipment ratings or contractual conditions matter, consult their current authoritative documents. An illustrative estimate is not a substitute for that verification.

• Reproduce the example before changing inputs
• Check all units and assumptions, including any default values
• Verify official or manufacturer-specific requirements outside the calculator