How it works
What this calculation includes
The balance after k years is S(1 + r)^k plus C((1 + r)^k - 1) / r. Setting that equal to the target T and solving for k gives the formula above.
With a target of $1,500,000, a current balance of $285,000, $42,000 added each year and a 6% real return, the result is 13.79 years.
At a zero return the balance grows only by contributions, so the time is the shortfall divided by the yearly contribution. If the current balance is already at or above the target, the time is zero.
Years to a savings target
In words Solve for the time when today’s balance, grown at a real return with a yearly contribution, reaches the target.
- Years to the target
- Target balance
- Current savings
- Contribution added at the end of each year
- Real (after-inflation) annual return
If r = 0, n = (T − S) ÷ C.
Example
- Target T: $1,500,000.00
- Saved S: $285,000.00
- Yearly contribution C: $42,000.00
- Real return r: 6%
- n = ln((T·r + C) ÷ (S·r + C)) ÷ ln(1 + r)
- Computed years = 13.79
Years to target: 13.79 years
Worked example
Using the default inputs on this page.
- Target balance
- $1,500,000.00
- Withdrawal rate
- 4.00%
- Current balance
- $285,000.00
- Contribution per year
- $42,000.00
- Real annual return
- 6.00%
Estimated time to target
13.79 years
About 13 years, 9 months to reach $1,500,000
Questions
What does a real return mean?
A return after inflation. Using a real return keeps the target and contributions in today's dollars.
When are contributions added?
At the end of each year, after that year's growth.
Why is the answer not a whole number?
The formula solves for the time at which the balance equals the target, which can fall part way through a year. The table shows whole years.
What does the withdrawal rate do?
It only sizes the yearly income a balance equals, as the balance times the rate. It does not change the years to target.
Sources
- Compound interest calculator U.S. Securities and Exchange Commission, Investor.gov. Retrieved 2026-10-11.