The effective annual return on savings or investments accounting for compound interest.
Annual Percentage Yield (APY) represents the total return you earn on a savings account, money market account, or CD over one year, including the effect of compound interest. APY is always equal to or higher than the stated interest rate because it factors in how often interest compounds. For example, a savings account earning 4% annual interest compounded daily will have a slightly higher APY than 4% due to the compounding effect. Banks and financial institutions must disclose APY to help consumers compare savings products. APY is the standard way to compare the true earning power of different savings vehicles.
APY is defined and disclosed under federal Regulation DD, which implements the Truth in Savings Act of 1991. The standard formula is APY = (1 + r/n)^n − 1, where r is the nominal annual interest rate and n is the number of compounding periods per year. Examples: 4.00% nominal rate compounded monthly → APY = (1 + 0.04/12)^12 − 1 ≈ 4.074%; compounded daily → APY = (1 + 0.04/365)^365 − 1 ≈ 4.081%. Continuous compounding gives the upper bound: APY = e^r − 1 ≈ 4.081% for r = 4%. Regulation DD requires depository institutions to advertise APY rather than the nominal rate so consumers can directly compare offerings that have different compounding frequencies. The FDIC publishes monthly National Rates and Rate Caps that summarize the national average APY across savings accounts, money market deposit accounts, and CDs by term. Common mistakes: (1) comparing APY to APR — APY measures savings returns including compounding, APR measures borrowing cost typically excluding compounding effects, (2) ignoring tax — APY is the PRE-tax yield; the after-tax yield is APY × (1 − marginal_tax_rate) for taxable accounts, (3) confusing promotional APYs with permanent APYs — many high-yield offerings include teaser rates that drop after an introductory period, (4) overlooking minimum-balance requirements — many advertised APYs require maintaining a threshold balance, (5) chasing tiny APY differences without considering FDIC insurance limits ($250,000 per depositor per insured bank per ownership category). For high-yield savings comparisons, the FDIC and FRED data give a free, public baseline.
The standard formula is APY = (1 + r/n)^n − 1, where r is the nominal annual interest rate (expressed as a decimal, e.g., 0.04 for 4%) and n is the number of compounding periods per year. For a 4% nominal rate compounded daily (n=365), APY = (1 + 0.04/365)^365 − 1 ≈ 4.081%. The formula is mandated under Regulation DD (the Truth in Savings Act) for U.S. depository institutions so that all advertised yields are directly comparable regardless of compounding frequency.
"Good" is relative to the current rate environment. The FDIC publishes a monthly National Rate for savings accounts that reflects the national average across all FDIC-insured institutions. High-yield online savings accounts typically pay multiple percentage points above the FDIC national average. The federal funds rate (set by the FOMC) anchors the upper bound — when fed funds is at, say, 5.25-5.50%, top high-yield savings APYs cluster in the 4.0-5.0% range. When fed funds is near zero, top savings APYs compress toward zero. Always compare against the current FDIC National Rate as the baseline.
No. The interest rate (also called the nominal rate or stated rate) is the periodic rate applied to your balance before considering compounding. APY incorporates how often that interest compounds during the year. For an account paying interest annually with no compounding, APY equals the nominal rate. For any account with intra-year compounding (monthly, daily, or continuous), APY is strictly higher than the nominal rate. Regulation DD requires APY disclosure so consumers can compare apples to apples.
Yes — interest earned in a taxable savings account is reported on IRS Form 1099-INT and taxed as ordinary income at your marginal federal tax bracket plus state income tax where applicable. The disclosed APY is a PRE-tax figure. Your after-tax yield is APY × (1 − marginal_tax_rate). Interest earned within a tax-advantaged account (Traditional IRA, Roth IRA, 401(k), HSA) is not subject to current-year tax. CalcFi does not provide tax advice — see IRS Publication 550 (Investment Income and Expenses) for authoritative guidance.
Online-only banks have lower operating costs — no physical branches, smaller staff, less overhead — and pass some of those savings to depositors as higher APYs. Traditional brick-and-mortar banks rely on branch convenience as a competitive moat and pay correspondingly lower yields. Both are typically FDIC-insured up to $250,000 per depositor per insured bank per ownership category, so the difference is purely yield and channel preference. The FDIC website lets you verify any bank's insured status.
APY applies to deposit accounts and CDs — it reflects the effective annual return assuming you keep the money in the account through one compounding cycle. Yield-to-Maturity (YTM) applies to bonds: it is the total return an investor would earn if the bond is held to maturity, accounting for coupon payments, the difference between purchase price and face value, and reinvestment of coupons. APY is a depository-account concept; YTM is a fixed-income-investing concept. They are not directly comparable across products.
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