$10,000 growing 1% a day for 365 days becomes $377,834.34, or $132,909.85 if it only grows on weekdays
The daily compound growth calculator starts with a balance, adds a gain every day, and lets each day's gain earn its own gain the next day. Put $10,000 at 1% a day for 365 days and you end with $377,834.34, which is 37.78 times the start. The balance doubles on day 70, passes five times the start on day 162 and passes ten times on day 232. If the same 1% only applies on weekdays, the year that starts on October 16, 2026 has 260 compounding days and the result is $132,909.85, only 13.29 times the start.
The calculator counts real calendar days. You can enter a daily return or a yearly rate, restrict growth to weekdays, reinvest only part of each day's gain, add money every day, week or month, and set a goal to find the day you reach it. The calendar under the result gives each day its own square, so you can see when the balance starts to pick up speed.
When you need a daily calculation
Daily compounding turns up in a few everyday places. The first is a savings account. Banks quote a yearly rate, and an account that accrues interest daily is effectively applying the yearly rate divided by 365 each day. How and when interest is added to the balance is set in the account's terms, so check the disclosure of the account you are comparing. The yearly-rate setting in this calculator models daily accrual that is added to the balance every day.
The second is a daily return target. Traders and hobby investors sometimes aim for "0.3% a day". The calculator shows what that target is worth if it were met on every day of the year, what it is worth if it only applies on trading days, and what changes if you pull half of each day's gain out. The third is a small daily habit. Add $5 every day to $100 at a tiny daily rate and the page shows how much of the final balance is your own money and how much is growth.
How the calculation works
- Enter the starting amount.
- Enter the rate and choose its basis. "Per day" applies the rate you type every day. "Per year" divides it by 365 and applies that daily rate every day.
- Enter the period in days, months or years. Months and years are counted on the real calendar from the start date: one year from October 16, 2026 is 365 days, and one year from October 16, 2027 is 366 days. The limits are 3,650 days, 120 months or 10 years.
- Open the extra options to set the start date, whether growth applies every day or on weekdays only, the share reinvested, a goal amount, and extra money added with its frequency.
- The result shows the balance, a bar splitting it into the starting amount, deposits, growth and money set aside, and the days you reach 2×, 5× and 10×. The calendar and chart show the balance by day, and the table lists it every 7, 30 or 90 days, every year or every day.
With no deposits, the formula is balance = starting amount × (1 + daily rate)number of compounding days. For a yearly rate, the daily rate is the yearly rate ÷ 365. If you reinvest less than 100%, only that share of each day's gain is added to the balance and the rest piles up separately as money set aside. The Consumer Financial Protection Bureau describes compounding as earning interest on the money you saved and on the interest you have already earned, and this calculator repeats that step once per day. With deposits, each day's gain is credited first and the deposit is added afterward, so a deposit starts growing the next day. Amounts are rounded to the cent, and milestones such as 2× or your goal are judged on the amount shown on screen.
One year of daily growth at different rates
A small daily rate looks harmless, but it is multiplied 365 times. The table starts with $10,000 on October 16, 2026 and runs one year (365 days). "Weekdays only" means growth on the 260 weekdays in that year.
| Daily return | Every day (365 days) | Weekdays only (260 days) | Doubles on (every day) | Doubles on (weekdays only) |
|---|---|---|---|---|
| 0.05% | $12,001.59 | $11,387.91 | day 1,387 | day 1,943 |
| 0.1% | $14,402.51 | $12,967.62 | day 694 | day 972 |
| 0.3% | $29,842.87 | $21,789.27 | day 232 | day 326 |
| 0.5% | $61,746.53 | $36,574.30 | day 139 | day 195 |
| 1% | $377,834.34 | $132,909.85 | day 70 | day 98 |
0.1% a day works out to 44.03% over a year, and 1% a day works out to 3,678.34%. A return like 1% a day for a whole year is not something real investments deliver, so read that row as a picture of how compounding grows, not as a forecast. Limiting growth to weekdays makes the doubling day about 1.4 times later at the same daily rate.
A yearly rate compounded daily
If an account earns interest every day and adds it to the balance, the amount you really earn in a year is (1 + yearly rate ÷ 365)365 − 1. U.S. deposit rules express this as the annual percentage yield (APY). Appendix A to 12 CFR Part 1030 (Regulation DD) gives the formula as APY = 100 × [(1 + interest ÷ principal)365 ÷ days in term − 1], states it as an annualized rate based on a 365-day year, and has banks assume that principal and interest stay in the account for the whole term. The table starts with $10,000 and runs one year.
| Yearly rate | After 1 year, compounded daily | After 1 year, simple interest | Difference | Effective yield (APY) |
|---|---|---|---|---|
| 1% | $10,100.50 | $10,100.00 | $0.50 | 1.005% |
| 2% | $10,202.01 | $10,200.00 | $2.01 | 2.0201% |
| 3% | $10,304.53 | $10,300.00 | $4.53 | 3.0453% |
| 4% | $10,408.08 | $10,400.00 | $8.08 | 4.0808% |
| 5% | $10,512.67 | $10,500.00 | $12.67 | 5.1267% |
At low rates the gap between daily compounding and simple interest is small: at 2% it is $2.01 a year on $10,000. If the same 2% were added to the balance once a month instead of every day, the balance after a year would be $10,201.84, which is $0.17 less than daily crediting ($10,202.01). The idea behind APY is that it lets you compare accounts that add interest at different intervals on one yearly footing. Interest you earn is taxable income. The IRS says most interest is taxable in the year it is paid or credited to an account you can withdraw from without penalty, and you should receive Form 1099-INT if you were paid $10 or more. What you owe depends on your tax bracket, so for a rough after-tax figure, multiply the yearly rate by one minus your own tax rate before you type it in.
Weekdays only and trading days
If gains only happen when a market is open, fewer days compound. 2026 has 261 weekdays. The New York Stock Exchange lists 10 holiday closures in 2026, and all of them fall on weekdays: New Year's Day (January 1), Martin Luther King Jr. Day (January 19), Washington's Birthday (February 16), Good Friday (April 3), Memorial Day (May 25), Juneteenth (June 19), Independence Day observed (July 3), Labor Day (September 7), Thanksgiving (November 26) and Christmas (December 25). That leaves 251 trading days. The NYSE also closes early on November 27 and December 24, but those days still trade. The table starts with $10,000 and applies the same daily return that many times.
| Compounding days in the year | 0.3% a day | 1% a day |
|---|---|---|
| Every day, 365 days | $29,842.87 | $377,834.34 |
| Weekdays, 261 days (2026) | $21,854.63 | $134,238.95 |
| NYSE trading days, 251 days (2026) | $21,209.68 | $121,524.77 |
The weekdays-only option skips Saturdays and Sundays only and does not skip holidays. With no deposits, the result depends only on how many days compound. To remove holidays too, set growth to every day and enter 251 as the period. The balance is then the same as the trading-day row, but the dates in the calendar and table no longer match the real calendar.
Reinvestment: how much of the gain goes back in
The share reinvested is the part of each day's gain that is added back to the balance. At 100% all of it is added. At 50% half is added and the other half is counted as money set aside. At 0% the balance never grows, and everything you earn is set aside, which matches simple interest. The table uses $10,000 at 1% a day for 365 days.
| Share reinvested | Balance | Money set aside | Total |
|---|---|---|---|
| 100% | $377,834.34 | $0.00 | $377,834.34 |
| 75% | $152,913.21 | $47,637.74 | $200,550.95 |
| 50% | $61,746.53 | $51,746.53 | $113,493.06 |
| 25% | $24,877.07 | $44,631.20 | $69,508.27 |
| 0% (simple interest) | $10,000.00 | $36,500.00 | $46,500.00 |
Taking out half of each day's gain leaves a total of only 30% of the fully reinvested result. At 50% the balance grows like a 0.5% daily return, and the money set aside also comes from that balance, so it grows faster later in the year. The "Without reinvesting" row and the dashed chart line show the total you would have if the share reinvested were 0% under your current inputs.
Adding money every day, week or month
Extra money is added after that day's gain is credited, so it starts growing the next day. Daily deposits are made on every compounding day (every weekday if weekdays only is on). Weekly deposits are made on the same weekday as the start date, and monthly deposits on the same date each month (the last day of the month when that date does not exist). The table starts with $100 at 0.1% a day for 365 days and compares three ways of putting in a similar amount.
| How you add | Total put in | Balance after 1 year | Growth |
|---|---|---|---|
| $5 every day | $1,925.00 | $2,345.28 | $420.28 |
| $35 every week | $1,920.00 | $2,333.70 | $413.70 |
| $150 every month | $1,900.00 | $2,283.40 | $383.40 |
The totals put in are close, but earlier and more frequent deposits have more time to grow, so daily deposits earn the most. The monthly row also puts in less ($1,900.00 against $1,925.00) because 12 deposits of $150 are made in the year. For monthly saving with a yearly return, the compound interest calculator with contributions fits better.
Common mistakes
- Typing a bank rate as a daily rate: entering 2% as "per day" compounds 2% 365 times and gives about 1,377 times the start. A bank rate belongs under "Per year".
- Multiplying a daily return by 365: 0.1% a day is not 36.5% a year. Compounded it is 44.03%. In the other direction, an investment that rises 10% in a year gains 0.0261% a day, not 0.0274% (10 ÷ 365). A bank's yearly rate is different: it is divided by 365 to get the daily rate, so enter a bank rate as a yearly rate.
- Treating a month as 30 days: six months is not 180 days. It is 181 days from January 1, 2026 and 184 days from July 1, 2026. The calculator counts months and years on the real calendar.
- Forgetting market holidays: a daily return target can only be earned on days the market is open. With weekends and NYSE holidays removed, a year has 251 compounding days in 2026, not 365.
- Assuming daily calculation means daily compounding: an account can calculate interest every day and still add it to the balance only monthly. Check when interest is credited in your account's terms.
Limits
- It assumes the same rate every day. Real returns vary from day to day and can be negative, and a volatile path ends lower than a steady one with the same average.
- Taxes, fees and inflation are not calculated, and neither is the way a bank rounds interest to the cent each day.
- Weekdays only skips Saturdays and Sundays, not holidays or market closures.
- On a losing day the whole loss comes out of the balance, whatever share you reinvest.
- The period goes up to 3,650 days, 120 months or 10 years (10 years is 3,652 or 3,653 days, depending on the start date). Milestones and goals are searched only within 10 years of the start date, and when you reinvest less than 100% they are judged on the balance plus the money set aside. Results above $1,000,000,000,000,000 are not calculated.
As of The NYSE 2026 holiday list, the 12 CFR 1030 Appendix A formula and the IRS interest page were opened and checked on 2026-10-16. The numbers in the tables come from this calculator, and rates such as 0.3% a day or 2% a year are examples, not forecasts.
Sources
- 01NYSE - Holidays and trading hours2026 market holidays (10 weekday closures) and early closes on November 27 and December 24
- 0212 CFR Part 1030 (Regulation DD) Appendix A - Annual Percentage Yield Calculation (Cornell LII)APY formula, 365-day year, assumption that principal and interest stay on deposit
- 03CFPB - How does compound interest work?Compounding means earning interest on your savings and on the interest you have already earned
- 04IRS - Topic No. 403, Interest receivedInterest is taxable in the year it becomes available to you; Form 1099-INT at $10 or more
Frequently asked questions
What is $10,000 at 1% a day after 365 days?
$377,834.34. 1.01 to the power of 365 is about 37.78, so the balance is 37.78 times the start. It doubles on day 70, passes five times the start on day 162 and passes ten times on day 232. If growth only applies on weekdays (the 260 weekdays from October 16, 2026), the result is $132,909.85.
What is the effective yield of a yearly rate compounded daily?
It is (1 + yearly rate ÷ 365) to the power of 365, minus 1. A 2% rate gives 2.0201% and a 3% rate gives 3.0453%. $10,000 at 2% for a year becomes $10,202.01, which is $2.01 more than simple interest. Choose "Per year" as the rate basis to calculate it this way.
Is savings account interest compounded daily?
Interest can be calculated daily, but it only earns interest of its own once it is added to the balance. When that happens is set in the account's terms. If 2% is added every day, $10,000 grows to $10,202.01 in a year, and if it is added once a month the result is $10,201.84, which is $0.17 less.
Can I calculate weekdays only?
Yes. Open the extra options and set the days that earn interest to weekdays only, and Saturdays and Sundays add nothing. Holidays are not skipped. To remove market holidays too, leave it on every day and enter the number of trading days as the period. The NYSE lists 10 weekday closures in 2026, which leaves 251 trading days out of 261 weekdays.
What does the share reinvested mean?
It is the part of each day's gain that goes back into the balance, and the rest is counted as money set aside. For $10,000 at 1% a day for 365 days, 100% gives $377,834.34, 50% gives a balance of $61,746.53 plus $51,746.53 set aside ($113,493.06 in total), and 0% matches simple interest with a total of $46,500.00.
How do I convert between daily and yearly returns?
A yearly return is (1 + daily return) to the power of 365, minus 1. A daily return is (1 + yearly return) to the power of 1/365, minus 1. 0.1% a day is 44.03% a year, and an investment that gains 10% in a year gains about 0.0261% a day. Multiplying a daily return by 365 gives a simple-interest figure that is lower than the compounded result.
What happens if I add $5 every day?
Start with $100, add $5 every day and earn 0.1% a day for 365 days, and the balance is $2,345.28. You put in $1,925.00 and the growth is $420.28. Adding $35 a week instead gives $2,333.70, and adding $150 a month gives $2,283.40.
Are taxes and fees included?
No. Interest you earn on a savings account is taxable income: the IRS says most interest is taxable in the year it is paid or credited to an account you can withdraw from, and you should receive Form 1099-INT if you were paid $10 or more. Your tax rate depends on your bracket, so to estimate after tax, multiply the yearly rate by one minus your own tax rate before you enter it. Trading fees and taxes on investment gains also reduce the real result.