Time to Reach a Savings Goal Calculator
If you already know how much you can set aside each month, this calculator answers the other half of the question: how long will it take to reach your goal with that contribution? Like the monthly investment for a goal calculator, this uses the real return (adjusted for inflation) so the goal and the result are always in today's purchasing power.
How is it calculated?
Starting from the future value formula with periodic contributions, the number of months is solved for: months = ln[(goal + contribution/r) / (initial capital + contribution/r)] ÷ ln(1+r), where r is the real monthly rate (return adjusted for inflation). If your initial capital already reaches the goal, the result is immediate (0 months). If the contribution and return would never reach the goal, the calculator tells you so instead of giving a meaningless number.
Examples
5,000 initial, 200/month, goal of 50,000, 6% return, 2.5% inflation
It will take 166 months (13.83 years) to reach the goal.
No initial capital, 300/month, goal of 20,000, 5% return, 2% inflation
It will take 62 months (5.17 years) to reach the goal.