Using this daily compound calculator
This tool steps through each calendar day from your start date, applying interest on every compounding day and optionally skipping weekends. It shares the same two-column layout as our compound and simple interest calculators: configure inputs on the left, then click Calculate to populate totals and a breakdown on the right.
- Set principal and rate — enter the starting balance and yearly or monthly nominal rate.
- Define the horizon — combine years, months, and days from your start date.
- Choose compounding rules — include all seven days or business days only (252-day year), and pick how much daily interest is 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, table, and chart.
What is daily compounding?
Daily compounding applies interest every eligible day rather than monthly or annually. Each day’s earnings can themselves earn interest the next day, producing a higher effective yield than the quoted nominal rate. Savings products, money-market funds, and trading accounts often compound on a daily or business-day schedule.
Unlike a standard compound-interest calculator that uses a fixed number of periods per year, this simulator walks the actual calendar — respecting your start date, duration, and weekend settings.
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 increase both balance and total principal invested; withdrawals reduce the balance on schedule. The yearly table lists interest per year, cumulative interest, and running balance. Switch to monthly view or the stacked chart for finer detail. Export CSV after calculating to save the breakdown.
For standard periodic compounding (monthly, quarterly, etc.) without a day-by-day calendar walk, use the compound interest calculator. For linear interest on principal only, use the simple interest calculator.
Examples and use cases
Worked example
$10,000 at 5% yearly compounded daily (365 days, 100% reinvest) for 1 year:
- Daily rate ≈ 5% ÷ 365 ≈ 0.0137% per day
- Future value ≈ $10,512.67
- Effective annual yield ≈ 5.13% APY
Real-world use cases
- High-yield savings: Compare 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 20% — the simulator shows how payout fraction lowers effective yield.