Find the interest rate on any loan or investment. Enter what you know and get the rate instantly.
Knowing the interest rate on a financial product is fundamental to evaluating whether it is a good deal. Lenders and issuers often advertise monthly payments or total costs without prominently displaying the underlying rate. Our interest rate calculator works in reverse: enter what you know (principal, payment and term, or starting and ending amounts) and it finds the rate. This works for car loans, personal loans, mortgages, savings accounts and investments.
For simple interest, the rate is straightforward: Rate = Interest / (Principal x Time). If you lent $5,000 and received $750 in interest over 3 years, the rate is $750 / ($5,000 x 3) = 5.0% per year. For compound amortised loans (the kind used for mortgages, car loans and most personal loans), the interest rate cannot be solved directly from the payment formula — it requires an iterative numerical method. The payment formula is: PMT = P x [r(1+r)^n] / [(1+r)^n - 1], where P is principal, r is the monthly rate and n is the number of months. Given PMT, P and n, our calculator finds r by iteration (Newton-Raphson method), which converges to the exact answer in milliseconds. Use our savings calculator once you know the rate to project future savings growth, and our compound interest calculator to model investment growth at any rate over any period.
| Loan Type | Typical Rate Range (2026) | Rate Type | Key Comparison Metric |
|---|---|---|---|
| 30-year mortgage | 6.0% - 7.5% | Fixed or ARM | APR (includes fees) |
| 15-year mortgage | 5.5% - 7.0% | Fixed | APR |
| Auto loan (new) | 5.0% - 9.0% | Fixed | APR |
| Auto loan (used) | 7.0% - 14.0% | Fixed | APR |
| Personal loan | 7.0% - 36.0% | Fixed | APR |
| Credit card | 18.0% - 29.99% | Variable | APR |
| High-yield savings | 3.5% - 5.5% | Variable APY | APY (includes compounding) |
Three related but distinct terms appear in financial products and understanding them prevents costly comparison errors. The nominal interest rate is the stated borrowing or lending cost before accounting for fees or compounding frequency. APR (Annual Percentage Rate) on loans equals the interest rate plus all mandatory fees (origination fees, closing costs, mortgage insurance, annual fees) expressed as an annualised percentage — it is always equal to or higher than the interest rate and is the correct metric for comparing loan costs. APY (Annual Percentage Yield) on savings accounts accounts for the effect of compounding: a savings account paying 5% nominal rate compounded monthly has an APY of (1 + 0.05/12)^12 - 1 = 5.116%. For savings comparison, use APY. For loan comparison, use APR. Our simple interest calculator shows the difference between simple and compound growth at the same rate, and our investment calculator projects long-term portfolio growth at any expected return rate.
Dealers, lenders and retailers often obscure the true interest rate by presenting financing as a simple monthly payment. A car dealer says "just $450/month for 72 months on this $24,000 car." The total paid is $450 x 72 = $32,400. The interest paid is $32,400 - $24,000 = $8,400. But what is the actual rate? Enter $24,000 principal, $450 monthly payment and 72 months into our loan mode — the calculator finds a rate of approximately 9.8% APR. Compare this to what banks or credit unions offer directly before accepting dealer financing. The same reverse-calculation approach works for any "buy now pay later" offer, rent-to-own scheme or instalment plan where the rate is not stated but the payment amount and term are known. Our loan affordability calculator shows the reverse: given a rate and term, what payment can you afford.
| Loan Amount | Monthly Payment | Term (months) | Calculated Rate | Total Interest |
|---|---|---|---|---|
| $15,000 | $290 | 60 | 6.8% | $2,400 |
| $24,000 | $450 | 72 | 9.8% | $8,400 |
| $300,000 | $1,896 | 360 | 6.5% | $382,560 |
| $5,000 | $165 | 36 | 14.9% | $940 |
| $10,000 | $230 | 48 | 7.4% | $1,040 |
The effective annual rate (EAR) is the actual annual rate accounting for intra-year compounding. A nominal rate of 12% produces different effective rates depending on compounding frequency: annual compounding gives an EAR of exactly 12.0%, semi-annual gives 12.36%, quarterly gives 12.55%, monthly gives 12.68%, daily gives 12.75%, and continuous compounding gives 12.75% (e^0.12 - 1). The EAR formula is: EAR = (1 + r/n)^n - 1, where r is the nominal annual rate and n is the number of compounding periods per year. This matters most when comparing financial products with different compounding frequencies — a savings account offering 5.0% compounded monthly is actually slightly better than one offering 5.05% compounded annually. Use our compound interest calculator to model the full growth trajectory at any EAR over any time horizon.
Interest rates on consumer loans and savings accounts are ultimately driven by the Federal Reserve's federal funds rate, which is the overnight lending rate between banks. When the Fed raises rates (as it did aggressively in 2022-2023 to combat inflation), borrowing becomes more expensive and savings yields improve. When the Fed cuts rates, mortgages and auto loans become cheaper but savings accounts pay less. The prime rate (approximately federal funds rate plus 3%) directly influences variable-rate loans and credit cards. Fixed-rate mortgages are more closely tied to 10-year Treasury yields than to the federal funds rate directly. Understanding these relationships helps predict whether current rates are likely to rise or fall, informing decisions about whether to lock in a fixed rate now or wait for potential cuts. Our mortgage calculator shows exactly how a 0.25% rate change affects your monthly payment and total interest on any mortgage amount.
Interest rates are not fixed — they are negotiated and can be improved through specific actions before and during the borrowing process. Credit score is the biggest determinant of loan rates for individual borrowers. Improving your credit score from 680 to 760 can reduce a mortgage rate by 0.5-1.0 percentage points — on a $300,000 30-year mortgage, 0.5% lower saves approximately $100 per month and $36,000 over the loan term. To improve your credit score: pay all bills on time without exception (35% of FICO score), reduce credit card utilisation below 30% (30% of score), and avoid new credit applications in the 6-12 months before a major loan. Shopping multiple lenders matters significantly: mortgage rates from different lenders on the same day can vary by 0.5-0.75% for the same borrower. Getting quotes from at least three lenders takes two hours and can save tens of thousands over the loan term. Paying points (pre-paid interest) at closing reduces the rate — one point (1% of loan amount) typically reduces the rate by 0.25-0.375%. This makes sense if you plan to keep the loan long enough to recoup the upfront cost through lower monthly payments. Our loan affordability calculator shows exactly how a lower rate translates to a higher loan amount you can afford on the same budget, and our compound interest calculator shows how the same rate difference compounds over time in savings and investment scenarios.
Understanding your current interest rate on every debt you carry is the foundation of smart debt management. Many people hold multiple loans and credit cards without knowing the exact rate on each. Once you know the rate, you can prioritise which debts to pay off first (highest rate first, the avalanche method) and calculate exactly how much interest you are currently paying per month. If you have a loan with a rate higher than what lenders currently offer, refinancing may reduce your monthly payment and total interest significantly. Our savings calculator shows the return side of the equation, and our simple interest calculator handles straightforward interest calculations when compound methods are not needed. For a complete view of your borrowing costs, pair this interest rate calculator with our compound interest calculator to see exactly how any rate grows a balance over time whether you are saving or repaying.