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Where P = principal, r = annual rate, n = compounding periods/year, t = years, PMT = monthly contribution × 12/n.
After-tax interest = gross interest × (1 − tax rate).
How Money Market Account Interest Works
Money market accounts earn interest through compound interest — where each period's interest is added to the principal balance, and future interest is calculated on the larger combined amount. Most money market accounts compound daily and credit interest monthly, maximizing your earnings compared to less frequent compounding.
A = 25,000 × (1 + 0.0475/365)^(365×3) = $28,843
Total interest = $3,843 | Monthly avg = $107/month
Money Market Account Rates by Institution Type (2026)
| Institution Type | Typical APY Range | Note |
|---|---|---|
| High-yield online banks | 4.50%–5.25% | Best rates, no branches |
| Credit unions | 3.50%–5.00% | Member-owned, competitive |
| Regional banks | 1.00%–3.50% | Varies widely |
| National banks (big 4) | 0.01%–0.60% | Far below average |
| National average (FDIC) | ~0.60% | Dragged down by big banks |
Daily vs Monthly Compounding Impact
| APR | Monthly Compounding APY | Daily Compounding APY | Difference ($25K) |
|---|---|---|---|
| 4.00% | 4.074% | 4.081% | +$1.75/yr |
| 4.50% | 4.594% | 4.603% | +$2.25/yr |
| 5.00% | 5.116% | 5.127% | +$2.75/yr |
A money market account is an FDIC-insured savings account that typically pays higher interest rates. They often require higher minimum balances and may limit certain withdrawals per month.
APY (Annual Percentage Yield) is the effective annual return including compounding. Always compare APY — not APR — when comparing money market accounts.
A = P(1 + r/n)^(nt) where P is principal, r is annual rate, n is compounding frequency, and t is years. Most MMAs compound daily.
Competitive online banks offer 4.0%–5.25% APY in 2026. The FDIC national average is around 0.60%, dragged down by big banks paying near zero. Online banks consistently offer the best rates.
Yes. Money market interest is taxed as ordinary income. You receive a 1099-INT if you earn $10 or more in a year. Interest is taxed in the year it is credited.
A money market account is FDIC-insured (safe). A money market fund is a mutual fund investing in short-term debt — not FDIC-insured. Bank MMAs are safer; funds may offer slightly higher yields.
Most MMAs compound daily and credit interest monthly. Daily compounding maximizes returns, though the difference vs monthly compounding is small at typical balances.
FDIC covers up to $250,000 per depositor per insured bank per ownership category. Spread larger balances across multiple banks or account types for full coverage.
Yes, MMAs are liquid. Federal Regulation D previously limited certain withdrawals to 6/month (suspended in 2020), but some banks still enforce limits. Check your account terms.
Daily compounding at 4.5% APR gives 4.603% APY. On $50,000 the difference vs monthly compounding is about $12/year — small but grows with larger balances and longer timeframes.