Prime Rate Calculator

The prime rate is the benchmark interest rate that commercial banks in the United States charge their most creditworthy corporate customers. It serves as a critical reference point for a wide array of consumer and business lending products, from home equity lines of credit (HELOCs) to small business loans and credit cards.

The prime rate is not set by the federal government directly. Instead, it is determined by the nation's largest commercial banks and moves in lockstep with the Federal Funds Rate set by the Federal Open Market Committee (FOMC). By long-standing convention, the U.S. prime rate is approximately 3 percentage points (300 basis points) above the federal funds rate. When the Fed raises or cuts its target rate, the prime rate follows within days.

For example, if the federal funds rate is 5.50%, you can expect the prime rate to be around 8.50%. This 3% spread has held remarkably stable for decades and is published daily by The Wall Street Journal based on surveys of the 10 largest U.S. banks.

Because so many loans are indexed directly to the prime rate, even a single 0.25% (25 basis points) change in the federal funds rate ripples through to every prime-based loan balance nationwide. Homeowners with HELOCs, small business owners with revolving credit lines, and consumers carrying variable-rate credit card balances all feel the impact immediately.

This prime rate calculator lets you enter your loan principal, the current prime rate, any margin applied above or below prime, your loan term, and the current federal funds rate. It then calculates your effective interest rate, monthly payment, interest-only payment, total interest paid, and the payment impact of a hypothetical 0.25% rate hike — giving you a complete picture of your prime-based loan cost.

This calculator uses three core formulas to compute your prime-based loan costs. The starting point is always the effective rate, which is the prime rate adjusted by any lender margin.

Once the effective rate is established, the calculator derives your monthly amortizing payment using the standard loan amortization formula. It also computes the simpler interest-only monthly payment — which equals the outstanding balance multiplied by the monthly rate — useful for understanding revolving lines of credit or interest-only draw periods on HELOCs.

Finally, a rate sensitivity analysis recalculates your payment assuming the prime rate rises by 0.25% (one standard Fed move), showing exactly how much your monthly obligation would increase. This is especially important for variable-rate loan planning.

The relationship between the prime rate and the federal funds rate is one of the most reliable and consistent conventions in U.S. banking. The federal funds rate is the overnight lending rate that depository institutions charge each other for short-term reserve balances held at the Federal Reserve. The Federal Open Market Committee (FOMC) sets the target range for this rate at its scheduled meetings throughout the year.

The prime rate historically tracks the federal funds rate at a spread of exactly 300 basis points (3%). This relationship has been stable for over 30 years. When the FOMC raises rates by 25 basis points, banks immediately adjust their prime rates upward by the same amount, passing the cost directly to borrowers on variable-rate products.

This calculator includes a Rate Analysis section that compares the prime rate you enter against the "expected" prime (Fed Funds + 3%). If your entered prime rate differs from that expected value, the calculator will show you the variance — helpful for confirming current market data before modeling your loan costs.

Understanding this relationship matters for financial planning. If the Fed signals multiple rate hikes ahead, borrowers with prime-indexed loans should model the potential payment increases. Our calculator's 25-basis-point sensitivity analysis is a quick way to estimate the cost of one such move.

A large portion of the consumer and commercial lending market is priced as a function of the prime rate. Understanding which products use prime as their benchmark helps you identify your exposure to rate changes and use this prime rate calculator more effectively.

Home Equity Lines of Credit (HELOCs) are among the most common prime-indexed products for homeowners. A HELOC typically carries a rate of Prime + 0% to Prime + 2%, depending on the borrower's credit profile, loan-to-value ratio, and the lender's pricing. Because HELOCs are revolving and variable, your minimum payment changes each billing cycle as the prime rate moves.

Business Lines of Credit and Small Business Loans issued by commercial banks are frequently priced at Prime + a margin based on the business's creditworthiness, collateral, and financial history. A well-qualified business might borrow at Prime + 1%, while a higher-risk borrower might see Prime + 4% or more.

Credit Cards typically carry variable rates expressed as Prime + a large spread, often Prime + 12% to Prime + 20% for standard consumer cards. This is why Fed rate increases quickly translate into higher minimum payments for cardholders carrying balances.

Adjustable-Rate Mortgages (ARMs) and certain student loans may also be indexed to the prime rate, though many ARM products use SOFR (the Secured Overnight Financing Rate) as their index since the transition away from LIBOR.

• HELOCs: Prime ± 0–2%
• Business Lines of Credit: Prime + 1–5%
• Credit Cards: Prime + 10–20%
• SBA Loans: Prime + up to 2.75% (fixed spread set by SBA rules)
• Personal Lines of Credit: Prime + 3–8%

This prime rate loan calculator is designed to give you a fast, accurate picture of borrowing costs on any prime-indexed product. Here is a step-by-step guide to getting the most out of each input field.

Loan Amount: Enter the total principal you are borrowing or the balance on a revolving line of credit. For a HELOC, this is your current outstanding draw. For a business loan, it is the full loan amount.

Current Prime Rate: Enter the prime rate in effect today. As of mid-2026, the U.S. prime rate is tied to the federal funds rate plus 3%. You can verify the current rate from the Federal Reserve's published data or financial news sources. The calculator defaults to 8.5% as a reference point.

Margin: Enter the spread your lender applies above or below prime. A HELOC priced at "Prime minus 0.5%" would have a margin of −0.5. A business loan at "Prime plus 2%" would have a margin of +2. If your loan is priced exactly at prime, leave this field at 0.

Loan Type: Select the type that best matches your product. This helps you interpret the results in context — for example, HELOC borrowers may draw primarily on interest-only payments during the draw period.

Loan Term: Enter the full amortization term in years. For a 5-year business term loan, enter 5. For a 30-year HELOC repayment period, enter 30.

Fed Funds Rate: This reference field lets the calculator show how your prime rate compares to the theoretical expected value (Fed Funds + 3%) and helps you cross-check that your prime rate input is accurate.

Once all fields are filled in, the calculator instantly displays your effective interest rate, monthly amortizing payment, interest-only monthly cost, total interest over the loan term, and how much your monthly payment would rise if the prime rate increased by 0.25%.

Variable-rate loans linked to the prime rate expose borrowers to interest rate risk: when the Federal Reserve tightens monetary policy, loan costs rise. Effective financial planning requires understanding this risk and taking steps to manage it.

Modeling multiple scenarios is the first step. Use this calculator to compute your monthly payment at the current prime rate, then re-run it at prime + 1%, prime + 2%, and prime + 3% to see how your costs evolve under a sustained rate-rising cycle. If your cash flow can't support the higher-rate scenarios, consider reducing your balance or locking in a fixed rate while rates are relatively low.

Converting to a fixed rate is an option many borrowers exercise when they expect rates to rise. Refinancing a variable-rate HELOC into a fixed-rate home equity loan, or converting a revolving business line of credit into a term loan, eliminates future rate risk at the cost of giving up potential savings if rates fall.

Accelerating paydown on prime-based debt during high-rate environments is another effective strategy. Because the interest-only payment rises with each rate hike, paying extra principal reduces the balance on which interest accrues, lowering your effective cost even as the rate remains elevated.

Monitoring the FOMC calendar helps you anticipate changes. The Federal Open Market Committee meets eight times per year and releases its rate decisions publicly. Tracking the Fed's "dot plot" projections gives you advance insight into where rates are likely to head, allowing you to plan refinancings or paydowns before rate moves take effect.