How the calculators compute what they compute, where the data comes from, and what the site does and does not do. If you spot something wrong, email in and it gets fixed.
Every calculator on RateCompas uses standard loan math — the same amortization formulas lenders, loan officers, and financial software have used for decades. There is no proprietary algorithm and no "secret sauce." The numbers the site shows are derived entirely from the numbers you enter.
The standard amortization formula computes a fixed monthly payment that fully pays off the loan over its term:
M = P × (r × (1 + r)^n) ÷ ((1 + r)^n − 1)Where M is the monthly payment, P is the loan principal, r is the monthly interest rate (APR ÷ 12 ÷ 100), and n is the total number of monthly payments. When APR is 0%, the formula degenerates and the payment is simply P ÷ n.
Total paid over the life of the loan is M × n. Total interest is (M × n) − P. Origination fees, when entered, are added to the principal before computing the payment — this produces the "effective APR" shown on the personal loan calculator, which is higher than the quoted APR whenever fees are non-zero.
HELOCs are calculated as two phases. The draw period uses interest-only payments: (balance × APR ÷ 100) ÷ 12. The repayment period uses the full amortization formula above, with the stress-tested rate (current APR + 2% by default, adjustable) applied to the remaining balance over the repayment term. The payment shock callout is simply the difference between those two phase payments.
The payoff accelerator simulates month-by-month amortization with an extra payment applied to principal each month. It iterates until the balance reaches zero and reports the total months elapsed and total interest paid. The "savings" figure is the difference in total interest between the standard and accelerated schedules.
Break-even months is closing costs ÷ monthly savings. Lifetime savings is (current total interest remaining) − (new loan total interest) − (closing costs). When the refinance extends the loan term, the calculator flags it: a lower monthly payment with a longer term often increases total interest despite the rate drop.
APR ranges and rate information shown on the site come from public, published sources. Nothing on the site is based on proprietary data, scraped content from lender portals, or personalized quotes from any user.
Rate data is reviewed and updated periodically as market conditions shift. The site's disclaimer text explicitly notes that rates are illustrative and change frequently — to get an actual quote, you need to apply or pre-qualify with a lender directly.
When you run a calculation, the site sends the computed results to a large language model — specifically Anthropic's Claude — along with a summary of the loan's math. The model returns a three-to-four-sentence analysis that highlights what stands out for that specific loan: a high APR for the credit tier, fees that outweigh a rate improvement, a term that stretches the loan farther than it should, and so on.
The model receives only the calculated numbers and the calculator inputs you entered: loan amount, APR, term, credit tier label, monthly payment, total interest, fees, and any scenario-specific context (co-signer status for student loans, CLTV for HELOCs, break-even month for refinance). It does not receive your name, your IP address, your browser fingerprint, your credit report, or anything else that could identify you.
The model returns commentary about the loan's math. It is explicitly prompted to reference only the information provided, not to make up numbers, and not to give personalized financial advice. The response is shown to you verbatim — the site does not post-process or filter the AI's output beyond basic formatting. Like any language model, the AI can occasionally produce phrasing that sounds more confident than the underlying math warrants. The numbers shown in the calculator itself — monthly payment, total interest, break-even months, and so on — are computed by the formulas above, not by the AI, and are the authoritative output on the page.
The AI analysis is a second-opinion layer on top of the math the calculator already shows. It is not professional financial advice, it is not a substitute for reading the loan terms yourself, and it does not know about your financial situation beyond the numbers you entered. The phrase to keep in mind is "helpful context, not a recommendation."
The lender-match section that appears after a calculation shows three tier-appropriate lender categories for the credit tier you selected. The selection criteria are published and consistent:
Affiliate compensation does not affect ranking. A lender that pays a higher commission does not move up. A lender that pays a lower commission does not move down. A lender that pays zero commission can still appear — federal student aid, for example, is shown as a non-affiliate option on the student loan calculator when it is the right fit.
The current lender cards on calculator pages show generic tier descriptors ("Prime-tier lender match," "Credit union tier," etc.) rather than branded lender names. Branded cards with tracked affiliate links will be swapped in as specific affiliate programs are approved. Every branded placement will carry the site's advertiser disclosure.
RateCompas is a calculator and analysis tool. A few things it explicitly is not:
The rate ranges and promotional terms shown on tier-based lender cards (for example, "8.0%–10.5%" or "0% intro APR") are illustrative figures, not offers. They are meant to help you sanity-check a quote you have received and set expectations before shopping the market.
Ranges are informed by publicly available sources, including the Federal Reserve's G.19 Consumer Credit report — which publishes weighted-average APRs by loan category — and rate tables published on personal-finance sites such as NerdWallet and Bankrate, which periodically survey advertised lender rates by credit tier. Each range represents an approximation of what borrowers in a given credit tier typically see when shopping multiple lenders. None of the ranges are personalized quotes, none are guarantees, and none are sourced from the proprietary or non-public pricing of any specific lender.
Because lender pricing changes frequently and varies by region, loan amount, term, and full underwriting, the ranges shown on the site are a starting point, not a finishing point. Verify current rates with individual lenders before making borrowing decisions.
RateCompas is an independent publisher. The site is run by one person (see About). Decisions about what to cover, how calculators behave, and which tier-descriptions appear in lender-match sections are editorial — they are not directed by lenders, advertisers, or any outside party.
If a calculator output is wrong, a rate range is stale, or a claim on an article page is inaccurate, the fix gets made as soon as it is verified. Material corrections to published articles are noted with an "Updated" date on the article byline. Calculator math fixes are deployed immediately without a changelog entry on the calculator page itself, because calculator pages do not carry "updated" dates the way articles do.
Rate-dependent content (credit-tier ranges, disclaimers, live Freddie Mac pulls) is reviewed when rates move materially, typically no less than monthly. Articles are reviewed on publication and again when related site content changes — for example, if a calculator's output format changes, articles referencing that output get updated in the same sweep.
The AI analysis shown on calculator result pages is generated per-request and is not cached, stored, or reviewed before display. It is clearly labeled as AI analysis on the page. Article content on the blog is written by the site author and is not AI-generated.
If you have spotted a calculation error, an outdated rate range, a lender recommendation that seems wrong, or a claim on an article page that does not match the source data, email contact@ratecompas.com. Include the page URL and what specifically looked wrong — the more specific, the faster the fix.
Methodology questions, press inquiries, and partnership questions go to the same address. The site is small; it is always answered by the author.