Mortgage Comparison Calculator

What a mortgage comparison should look at beyond monthly payment

Borrowers often start by asking which loan has the lowest monthly payment, but that is only one part of the decision. A mortgage offer can have a slightly lower payment because the rate is lower, because the term is longer, or because some costs have been shifted into upfront fees, lender credits, or a different APR profile. Comparing the quote properly means reading the monthly payment together with the note rate, APR, term, and cash needed at closing.

That is why this calculator compares several lenses at once. Monthly payment helps with affordability, APR helps compare rate-plus-fee structure on a standardised annual basis, upfront costs show how much cash the quote needs on day one, and the holding-period comparison shows how much of that decision still matters if you refinance, sell, or move before the full term ends.

The terminology on this page aligns most closely with the US Loan Estimate and Closing Disclosure format used by the Consumer Financial Protection Bureau. The amortisation maths itself is general fixed-rate mortgage maths, but the APR and closing-cost framing is easiest to interpret when you are comparing lender paperwork that follows that same quote structure.

How the mortgage comparison maths works

Each offer starts with the standard fixed-rate amortisation formula to calculate the monthly principal-and-interest payment from the loan amount, note rate, and term. The calculator then simulates scheduled payments through your chosen holding period so it can separate how much interest you would have paid, how much principal would have been repaid, and how much balance would still remain at that point.

That holding-period view matters because principal is not pure borrowing cost in the same way interest and fees are. If you keep a mortgage for seven years and then refinance or sell, the main comparison is usually the upfront costs plus the interest paid during those seven years, while the remaining balance tells you how much debt is still outstanding. That is a more useful planning lens than lifetime interest alone when you do not expect to keep the same loan for the entire term.

Worked example: lower rate, higher fees versus lower upfront cash

Suppose you are comparing two 350,000 fixed-rate mortgage offers over a seven-year planning horizon. Offer 1 charges a 6.00% note rate with a 6.18% APR and 7,800 in upfront costs. Offer 2 charges a 6.375% note rate with a 6.48% APR and 2,400 in upfront costs. Offer 1 asks for more cash at closing, but the lower rate reduces both the monthly payment and the interest paid over time.

On a full 30-year schedule, Offer 1 usually wins on lifetime cost because the lower note rate reduces total interest enough to overcome the extra closing cost. The more interesting question is what happens before year 30. If the lower-rate option saves roughly 80 to 90 per month, the extra upfront cost can be recovered in a little over five years. A borrower likely to refinance again in two or three years may prefer the cheaper upfront offer, while a borrower planning to stay in the loan beyond the break-even point may rationally choose the higher-fee quote.

That is why the holding-period result belongs next to the lifetime view. It prevents the common mistake of treating a full-term interest saving as if it automatically applies to someone who expects to move or refinance long before the mortgage matures.

How to use Loan Estimates without over-trusting any one number

APR is useful, but it is not a complete tie-breaker. CFPB guidance makes the same point explicitly: APR includes many upfront fees, while other disclosures such as the Total Interest Percentage and cash-to-close figures show different parts of the quote. Two offers can sit close together on APR while still asking for very different upfront cash or producing different payment paths if the term length changes.

Use the calculator as a structured shortlist, not a final lending decision. Compare note rate, APR, points or fees already included in your upfront-cost figure, the monthly payment you can actually afford, and the period you realistically expect to keep the loan. Then check the lender's formal Loan Estimate for mortgage insurance, escrow, taxes, prepaid interest, rate-lock timing, and any lender credit conditions that are not explicitly modelled here.

This tool also does not pull live market rates. It compares the numbers you enter from actual quotes, which means the result is only as current as the lender paperwork you are comparing. If a rate lock expires or the lender revises fees, rerun the comparison with the new figures before relying on the result.

What this mortgage comparison calculator does not cover

This calculator models fixed-rate principal-and-interest comparisons only. It does not project adjustable-rate mortgage resets, future refinancing costs, mortgage insurance cancellation, escrow collection, taxes, homeowners insurance, HOA dues, seller concessions, or rate-lock extensions unless you manually reflect those items in the upfront-cost field. If those items differ materially between quotes, the calculator should be treated as an early planning filter rather than a complete total-housing-cost model.

It also cannot tell you whether a mortgage is affordable for your wider financial picture. A quote that looks cheapest on interest may still be the wrong choice if it strains your cash reserves, emergency fund, debt-to-income ratio, or expected time in the property. For borderline affordability, unusual loan structures, or any case where the lender paperwork is hard to interpret, an independent mortgage broker or regulated financial adviser is the safer next step.