Daily Compound Interest Calculator
Calculate daily compound interest on savings accounts, money market funds, and high-yield accounts. See how daily compounding accelerates growth.
Total Interest (Daily Compounding)
$2,842
Future Value
$12,842
APY
5.127%
Days
1,826
What is Daily Compound Interest?
Daily compound interest is interest calculated and added to your balance every single day โ 365 times per year. Each day, you earn interest not just on your original principal, but on all the interest previously earned. Over time, this compounding effect creates exponential growth that far exceeds simple interest or even monthly compounding.
The Daily Compound Interest Formula
A = Final amount | P = Principal | r = Annual interest rate (decimal) | t = Time in years
Example: $10,000 at 5% annual rate, compounded daily, for 10 years:
A = $10,000 ร (1 + 0.05/365)^3,650 = $10,000 ร 1.6487 = $16,487
Interest earned: $6,487 (vs $5,000 with simple interest โ 30% more)
Daily vs Monthly vs Annual Compounding
| Compounding Frequency | $10,000 at 5% after 10 years | Effective APY |
|---|---|---|
| Annual | $16,288.95 | 5.000% |
| Quarterly | $16,436.19 | 5.095% |
| Monthly | $16,470.09 | 5.116% |
| Daily | $16,487.21 | 5.127% |
| Continuous | $16,487.21 | 5.127% |
The difference between daily and monthly compounding is small for savings accounts, but on large balances or long time horizons, even basis-point differences become meaningful.
Where Daily Compounding Matters Most
- Credit cards: Most US credit cards compound daily. A 20% APR card has an effective APY of 22.13% โ costing you significantly more than the headline rate suggests
- High-yield savings accounts and CDs: Most premium savings accounts and online banks use daily compounding, giving you a slight edge over traditional monthly-compounding accounts
- Money market accounts: Typically compound daily, making it important to compare APY (which accounts for compounding) rather than APR
- Margin and brokerage loans: Typically compound daily โ can erode returns significantly if positions are held long-term
The Rule of 72 โ Quick Doubling Time Estimate
Divide 72 by your interest rate to estimate how many years it takes to double your money:
- 5% rate โ 72/5 = ~14.4 years to double
- 7% rate โ 72/7 = ~10.3 years
- 10% rate โ 72/10 = ~7.2 years
- 12% rate โ 72/12 = ~6 years
References
- Federal Reserve โ Truth in Lending Act: compounding disclosure requirements
- Federal Truth in Savings Act โ APY calculation mandate (12 CFR Part 1030)