Using this daily compound calculator
This tool steps through each calendar day from your start date, applying interest on every day that qualifies and optionally skipping weekends along the way. It follows the same two-column layout as our compound and simple interest calculators: configure everything on the left, then hit Calculate to fill in totals and a breakdown on the right.
- Set principal and rate: enter the starting balance and a yearly or monthly nominal rate.
- Define the horizon: combine years, months, and days starting from your chosen date.
- Choose compounding rules: include all seven days or stick to business days only (a 252-day year), and decide how much of the daily interest gets reinvested.
- Add contributions (optional): schedule deposits or withdrawals monthly, quarterly, half-yearly, or yearly.
- Review results: future value, total interest, effective compounded rate, rate of return, doubling time, a table, and a chart.
What is daily compounding?
Daily compounding applies interest on every eligible day instead of waiting for a monthly or annual cycle. Since each day’s earnings can themselves earn interest the next day, the effective yield ends up a bit higher than the quoted nominal rate. Savings products, money-market funds, and trading accounts often run on a daily or business-day compounding schedule.
Where a standard compound-interest calculator assumes a fixed number of periods per year, this one actually walks the calendar, respecting your start date, duration, and weekend settings the whole way through.
Daily balance update
On each compounding day the balance grows by a fraction of the annual rate divided by the day count (365 calendar days or 252 trading days):
r = annual rate, D = 365 or 252 trading days, f = reinvest fraction
When reinvest is below 100%, only the fraction f of each day’s interest is added back to the balance; the remainder is treated as paid out and does not compound further.
Effective annual yield
With full reinvestment, daily compounding approaches:
When 100% of daily interest is reinvested
The results panel shows the realized compounded rate over your exact modeled period, which also reflects partial reinvestment, contributions, and skipped weekends.
Calendar vs trading-day compounding
| Setting | Days per year | Typical use |
|---|---|---|
| Include all days (Yes) | 365 | High-yield savings, advertised daily APY |
| Weekdays only (No) | 252 | Equity and forex-style business-day accrual |
Contributions and breakdown
Regular deposits bump up both the balance and total principal invested, while withdrawals pull the balance down on schedule. The yearly table breaks out interest per year, cumulative interest, and running balance, or switch to the monthly view or stacked chart when you need finer detail. Once you’ve calculated, export a CSV to keep the breakdown for later.
Looking for standard periodic compounding (monthly, quarterly, and so on) without the day-by-day calendar walk? The compound interest calculator handles that. Need fixed-rate certificates of deposit with tax modeling? Try the CD Calculator. For plain linear interest on principal only, the simple interest calculator is the right tool.
Examples and use cases
Worked example
Put $10,000 at 5% yearly, compounded daily over 365 days with full reinvestment, and run it for a year:
- The daily rate works out to roughly 5% ÷ 365, about 0.0137% per day
- Future value lands around $10,512.67
- Effective annual yield comes to roughly 5.13% APY
Real-world use cases
- High-yield savings: compare the advertised “daily compounding” APY on two online banks by modeling the same deposit over 12 months.
- Trading account accrual: a forex trader sets weekdays-only compounding to approximate business-day interest on a margin balance.
- Partial reinvestment: a retiree reinvests 80% of daily money-market interest and withdraws the rest, and the simulator shows exactly how that payout fraction drags down the effective yield.