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Loan Comparison Calculator

Compare two loan offers side-by-side: payment, total interest, total paid, and payoff date.

  • loan
  • mortgage
  • compare
  • refinance
  • amortisation
  • rate
  • side by side

About Loan Comparison Calculator

Two loan offers with different rates, terms, or extra payments don't compare cleanly in your head. A lower monthly payment might cost tens of thousands more in total interest. A higher rate might still win if its term is shorter. Adding $100 extra to the principal each month might shave four years off the payoff but it depends on the other terms.

This calculator runs the full amortisation schedule for two loans simultaneously and shows the differences across all the metrics that matter: scheduled payment, total interest, total amount paid, and payoff date. The differences are colour-coded — green means Loan B wins on that line, red means Loan A. Built on the same amortisation engine as the mortgage calculator, so the numbers are cent-accurate (no floating-point drift over 360 monthly steps).

How to use

Enter principal, annual rate, term in years, and any extra per-period payment for each loan. The payment frequency (monthly, fortnightly, or weekly) and currency apply to both sides. Results update instantly — there's no calculate button.

The comparison table shows each metric for both loans and the B-minus-A delta. The delta is colour-coded relative to which loan is better: green if B beats A (e.g. lower total interest), red if A wins. Payoff date difference is shown in years and months. Bookmark the URL to save a specific comparison or share it.

Frequently asked questions

  • When is a lower rate not the better loan?

    When the lower-rate loan has a much longer term. A 30-year mortgage at 5.0% has a smaller monthly payment than a 25-year mortgage at 5.5%, but you pay interest for five extra years — the total interest is usually higher despite the lower rate. The "total paid" line in the comparison table is the cleanest way to see this: it's the sum of every payment over the life of the loan.

  • Do extra payments really help that much?

    Often dramatically, because every dollar paid to principal early avoids years of compounding interest on that dollar. Adding $100/month to a $400k 30-year mortgage at 5.5% saves roughly $45,000 in interest and shaves about 3 years off the payoff. The earlier in the schedule the extra dollar lands, the more interest it avoids — extras in year 1 are worth far more than the same dollar in year 25.

  • Should I compare on monthly payment or total paid?

    Depends on your constraint. If cashflow is tight, monthly payment is the metric that determines whether you can afford the loan at all. If you can afford either payment, total paid (or its proxy, total interest) is the better single comparison — it's the lifetime cost of borrowing. Most refinance decisions hinge on whether the lower monthly is worth the extra months of payments tacked onto the back.

  • How does payment frequency affect the comparison?

    Fortnightly and weekly payments amortise the loan slightly faster than monthly, even at the same annual rate, because each payment shaves a bit more principal off before interest compounds again. The effect is small but cumulative: a fortnightly mortgage pays off a few months sooner than the equivalent monthly schedule. Both loans use the same frequency here so the comparison isolates the rate/term/principal differences.

  • Are these results bank-accurate?

    The maths is standard amortisation and the calculation uses decimal.js, so the cents won't drift over hundreds of payments. But real lenders add fees (origination, broker, mortgage insurance), prepayment penalties, and rounding rules that this tool doesn't model. Use it for "which loan is structurally better" — confirm the exact dollars on the loan documents before signing.

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