Daily compound interest calculator
Enter an initial deposit, an optional regular contribution and a rate, with compounding fixed to daily (365 times a year) -- the way most high-yield savings accounts, money market accounts, and many CDs actually credit interest. Get the final balance, total interest, effective annual yield, a year-by-year table and a growth chart.
Start = deposited before that day's interest; end = after.
Final balance
$51,022.02
Total contributions
$24,000.00
+ $10,000 initial
Total interest
$17,022.02
Effective annual yield (APY)
6.18%
vs. 6% nominal
Balance over time
How daily compounding is calculated
Daily compounding is the standard compound interest formula with the compounding count fixed at 365 (or 366 in a leap year, though this tool uses 365 for simplicity):
A = P × (1 + r/365)365×t
where A is the final balance, P the principal, r the nominal annual rate as a decimal, and t the number of years. Every day, the balance is multiplied by (1 + r/365); over a full year that compounds up to the account's Annual Percentage Yield, APY = (1 + r/365)365 − 1, which at a 6% nominal rate works out to 6.1831% -- see the APY calculator to check any rate. Regular contributions are added into the balance the same way as the site's main calculator: at the start of each period they earn that period's interest too, at the end they don't until the following one.
Worked example
$10,000 initial deposit, $200 contributed at the end of every month, a 6% nominal annual rate compounding daily, over 10 years:
| Growth of the $10,000 initial deposit alone | $18,220.29 |
| Growth of the $200/month contributions | $32,801.73 |
| Final balance | $51,022.02 |
| Total contributed over 10 years | $34,000.00 |
| Total interest earned | $17,022.02 |
Plug the same four numbers into the calculator above and it lands on the same $51,022.02 to the penny -- checked against this exact worked example in the site's own test suite, not just written here.
Frequently Asked Questions
How exactly is interest calculated when it compounds daily?
The bank divides the nominal annual rate by 365 to get a daily periodic rate, then multiplies the current balance by that rate every day and adds the result back in -- so tomorrow's interest is calculated on today's balance plus today's interest. At 6% nominal, that's a periodic rate of 0.01644% applied 3,650 times over 10 years. Run it forward on a $10,000 deposit with no contributions and it reaches $18,220.29, versus $18,193.97 for monthly compounding at the identical nominal rate.
Does my bank really compound daily, or just say it does?
Many do compound daily internally but only post (credit) the accumulated interest to your visible balance monthly or quarterly -- your account statement shows one number, but the bank's own ledger accrues daily behind it. The end result to you is the same either way, since the interest for each day it's owed still gets added into the base the next day's interest is calculated on; it's just displayed in a batch. Check your account's disclosure or Truth in Savings statement for the exact wording if it matters for your own reconciliation.
How much more do I earn with daily compounding versus monthly or annual?
Less than most people assume, and it shrinks as the comparison point gets more frequent. On $10,000 at 6% for 10 years with no contributions: annual compounding reaches $17,908, monthly reaches $18,194, and daily reaches $18,220. Daily beats annual by $312 here, but daily beats monthly by only $26 -- under half a percent of the balance. The rate and the number of years you stay invested matter far more than whether crediting happens daily or monthly.
Need a different compounding frequency to match your own account, or want to compare several side by side? The full compound interest calculator lets you pick any of them, and the savings interest calculator is a simpler version built around the savings-account case specifically. Figures on this page are estimates for general education, not investment or tax advice.