Savings time calculator
Estimate how long a contribution plan may take.
- Formula and assumptions shown
- Table and CSV export
- Runs in your browser
How it works
The calculator grows the starting balance and recurring deposits month by month until the target is reached. It reports the first modeled month at or above the target rather than hiding the rounding in a closed-form answer.
Each month: interest = prior balance × (annual rate ÷ 12); ending balance = prior balance + interest + month-end contribution; stop when balance ≥ target.
If contributions cannot reach the target under the selected assumptions, the result explains why. A changing rate, missed deposit, or withdrawal will alter the actual timeline.
Assumptions
- Contributions are equal and added at month end after interest is calculated.
- The nominal annual rate is divided by 12 and stays constant.
- If the target is at or below starting balance, the required time is zero months.
- The model has a bounded 600-month horizon and excludes fees, taxes, and withdrawals.
Worked example
$1,000 target at $100 monthly
With $0 starting balance and 0% interest, ten end-of-month contributions reach $1,000.
Step by step
- Find the monthly rate. At 0% the monthly rate is 0% ÷ 12 = 0, so each month adds interest of $0.00 and the balance grows only by deposits.
- Model the first month. Starting balance $0 + $0 interest + $100 month-end deposit = $100 after month 1.
- Repeat until the target is reached. After month 9 the balance is 9 × $100 = $900, still below the $1,000 target, so the model continues.
- Report the first month at or above the target. Month 10 brings the balance to $1,000, so the result is 10 months, with $1,000 of total contributions and $0 of interest.
- Try the same plan with interest. At 4%, the balance after month 9 is $912.09 and after month 10 is $1,015.13, including $15.13 of interest. Interest is too small here to save a month, so the answer is still 10 months.
How to read your result
Time to target is the first whole month in which the modeled balance reaches the target. Ending balance is the balance in that month, which usually overshoots the target slightly because deposits come in whole amounts. Total contributions and Interest earned split that ending balance, together with the starting balance.
The chart plots the balance month by month, and the table lists each month’s balance, interest, and deposit, starting from month 0. If the target is not reached within 600 months, the result says so and shows the projected balance at month 600 instead.
Deposits are modeled at the end of each month, after that month’s interest, at one constant rate. Missed deposits, withdrawals, rate changes, taxes, and fees all lengthen the real timeline, so running a lower rate or a smaller deposit shows how sensitive the date is.
What changes the result most
- Monthly contribution
- For a $50,000 target with $5,000 saved at 4%, $500 a month takes 77 months (6 years 5 months). Raising the deposit to $750 cuts that to 54 months (4 years 6 months).
- Rate
- For the same $50,000 goal at $500 a month, 0% takes 90 months, 4% takes 77 months, and 5% takes 74 months. The longer the timeline, the more the rate matters.
- Starting balance
- In the $1,000 example, starting with $300 instead of $0 cuts the time from 10 months to 7 months.
Questions
Why does the answer use a whole number of months?
Deposits are modeled monthly, so the first month that reaches the target is the useful planning result.
What if the target is below my current balance?
The goal is already reached under the entered starting balance, so the required time is zero months.
Can I include interest?
Yes. Enter an annual rate. The calculator applies its stated monthly convention and shows that the timeline depends on the assumed rate.
How long does it take to save $10,000?
It depends mostly on the monthly amount. From a zero balance at $500 a month, it takes 20 months at 0%. At 4% it is still 20 months, ending at $10,323.09 with $323.09 of interest, because over a short period interest adds little.
How long does it take to save a million dollars?
At $1,000 a month from zero, 0% never gets there within the 600-month limit ($600,000 after 50 years). At a constant 4% it takes 441 months (36 years 9 months), at 6% 360 months (30 years), and at 7% 331 months (27 years 7 months). Investment returns are not constant, so actual timelines vary.
More in Savings & investing
Sources
These references explain the concepts behind the calculation. They do not endorse this site. Estimates leave out any cost or condition you did not enter.