About the APR Calculator
An APR calculator computes the Annual Percentage Rate of a loan — the all-in cost of borrowing including interest plus most fees, expressed as a yearly rate. APR exists specifically to make loan offers comparable. A 6.5% rate with $5,000 in points and fees is more expensive than a 6.875% rate with $1,500 in fees; APR captures that gap in a single number.
Rate vs. APR vs. APY
The interest rate is the cost of borrowing the principal. APR adds origination fees, discount points, certain closing costs, and (on some loans) mortgage insurance into a single annualized cost figure. APY is a different concept entirely — it's the effective annual yield on a savings account, accounting for compounding. APR is for borrowing; APY is for saving.
For mortgages, the APR is calculated by computing what rate, applied to the loan amount, would produce the same monthly payment if all upfront fees were rolled in. This means APR depends on the assumed loan length: a 30-year APR overstates the true cost if you sell or refinance within 7–10 years (because the upfront fees haven't fully amortized).
When APR is the right comparison
APR is the right comparison when you'll keep the loan for the full term — at that horizon, the upfront costs distribute over enough years that APR captures the true cost of borrowing. For mortgages, that means APR is most useful for buyers planning to stay in the home 10+ years.
For shorter horizons, APR can be misleading. A higher APR with low fees can be cheaper than a lower APR with high fees if you only keep the loan 3–5 years. The right calculation in that case is total cost (interest + fees) over the actual expected time in the loan, not APR.
APR on credit cards: a different beast
Credit-card APR is the simple periodic rate × 365 (for daily compounding). Because the interest compounds daily and is charged on revolving balances, the effective annual rate on a credit card is slightly higher than the disclosed APR. Most credit-card APRs are also variable, indexed to the Prime Rate plus a margin.
Different APRs apply to different parts of the same card balance: purchases (the headline rate), balance transfers (often a different promotional rate), and cash advances (typically a higher rate, with no grace period). Always check the breakdown in the card's terms; the headline rate is only the starting point.
Why dealer financing APR ≠ headline rate
Auto-loan APR includes dealer-arranged financing markups. The bank approves you at a base rate (the "buy rate"), and the dealer marks it up before quoting you (the "sell rate"). The difference is dealer reserve — a major dealer profit center. A pre-approval from a credit union or bank gives you the actual buy-rate-equivalent and a benchmark to negotiate against.
On promotional manufacturer financing, the APR is genuine — the manufacturer subsidizes the rate as an incentive. These offers are often the cheapest financing available, but require strong credit and frequently force you to choose between the low rate and a cash rebate.
Formula
- loan amount = Stated principal
- net fees = Origination fees, points, and other prepaid finance charges (subtract from principal in the calculation)
- monthly payment = Computed using the contract rate
- r = Monthly APR (annual APR / 12) — solved iteratively
- n = Number of monthly payments
Worked examples
Rate vs. APR on a $300,000 mortgage
Option A: 6.5% rate, $5,000 in points and fees. Option B: 6.875% rate, $1,500 in fees. Monthly P&I: A ≈ $1,896, B ≈ $1,971 — A saves $75/month. APR on A ≈ 6.69%; on B ≈ 6.93%. APR captures both the interest and the points/fees in a single comparable number.
Break-even on points
Same loan: paying $5,000 in points to drop from 6.875% to 6.5% saves $75/month. Break-even = $5,000 / $75 ≈ 67 months (5.6 years). If you'll keep the loan longer than that, A wins. If you might refinance or sell sooner, B wins despite the higher APR.
Credit card APR vs. effective annual rate
Credit card with 22% APR on revolving balance: daily periodic rate = 22% / 365 = 0.0603%. Effective annual rate (compounded daily) = (1 + 0.000603)^365 − 1 ≈ 24.6%. The disclosed APR understates the true annual cost by ~2.6 points when balance is carried full-year.
Frequently asked questions
What's the difference between interest rate and APR?
The interest rate is the cost of borrowing the principal. APR includes the rate plus fees and certain costs, expressed as an annualized rate. APR is always equal to or higher than the rate; comparing across loan offers should be done APR-to-APR for the cleanest comparison.
Is a lower APR always better?
Usually yes — but only if you'll keep the loan to a horizon where the upfront fees fully amortize. For short-horizon loans (likely refinance or sale within 3–5 years), the loan with lower upfront fees and slightly higher rate can be cheaper than the lower-APR option.
What costs are included in mortgage APR?
Federally required: lender origination fees, discount points, mortgage insurance, and certain other prepaid finance charges. Not included: most third-party costs (title insurance, recording fees, appraisal, etc.), property tax escrows, and homeowners insurance. Lenders can vary slightly on what they include — comparing across lenders sometimes requires line-by-line cost comparison, not just APR.
How do I calculate APR on a loan?
Iteratively. Given the contract rate, term, and total prepaid finance charges, you solve for the rate that — applied to (loan amount − fees) — produces the same monthly payment as the contract rate applied to the full loan amount. Calculators and amortization tools do this automatically; doing it by hand requires Newton's method or trial-and-error.
Why is the APR on my mortgage different from my interest rate?
Because the APR rolls in upfront fees and points. If your loan estimate shows a 6.5% rate but a 6.69% APR, that 0.19% gap reflects the prepaid fees converted to a rate. A loan with no fees would have APR = rate (or very close to it).
Can APR be lower than the interest rate?
Almost never on standard loans — APR includes additional costs, so it's mathematically constrained to be at or above the rate. The exception: certain promotional loans where lender credits offset fees, in which case the disclosed APR can technically be slightly lower than the rate. This is rare in mainstream lending.