A savings goal calculator answers the question "how long will it take?" Enter your target amount, current balance, monthly contribution, and the rate of return you expect, the calculator returns the years (and months) to hit your number, plus how much of the final amount comes from your contributions vs. compounding interest.
Useful for retirement savings, down payments, college funds, or any long-term financial target. Treat the rate of return as your expected average, actual market returns vary wildly year-to-year, but for multi-decade horizons the average is what matters.
Key takeaway
Time and contribution amount are the two levers you control. Rate of return is mostly out of your hands. Of those two levers, time compounds non-linearly, adding 5 years to a 20-year horizon doesn't just add 25% to your final balance, it can add 50% or more depending on rate. Starting earlier dwarfs almost any other variable in long-term saving.
How it's calculated
The math solves the standard future-value-of-annuity equation for number of periods (n):
FV = P(1+r)^n + PMT × [(1+r)^n − 1]/r
Solving for n with FV = target, P = current balance, PMT = monthly contribution, and r = monthly rate:
n = ln((target × r + PMT) / (current × r + PMT)) / ln(1 + r)
The result is in months; divide by 12 for years.
Edge cases: if your monthly contribution is zero and current balance is zero, the math has no solution (you can't grow zero). If your target is less than your current balance, the formula returns zero or negative months, meaning you've already reached the goal.
Source: Future-value-of-annuity formula solved for periods (n)
Examples
$100K target, $10K current, $500/mo, 7% rate
- Savings target $100,000
- Current balance $10,000
- Monthly contribution $500
- Annual rate of return 7%
Reaching $100,000 from a $10,000 starting balance with $500/month contributions at 7% annual return takes about 9.5 years (114 months). Of the final balance, ~$57K comes from your contributions and ~$33K from compounding interest. The remaining $10K is your starting balance.
$1M retirement target, $50K current, $1,500/mo, 8% rate
- Savings target $1,000,000
- Current balance $50,000
- Monthly contribution $1,500
- Annual rate of return 8%
Hitting a $1M retirement target from a $50K balance with $1,500/month contributions at 8% takes ~18.7 years. Notable: more of the final million comes from interest ($613K) than from contributions ($337K), that's the compounding lever doing the heavy lifting on a long horizon.
Frequently asked questions
What rate of return should I assume?
For multi-decade equity investing, the historical US stock market average is around 10% nominal (7% after inflation). Bonds have averaged 4-5% nominal. A balanced 60/40 portfolio has averaged around 7-8% nominal. Most personal-finance calculators default to 7% as a reasonable real-return assumption, though there's no guarantee future returns will match the historical average, especially over shorter timeframes.
Should I count my employer's 401(k) match as part of my contribution?
Yes, count the total amount going into the account each month from all sources (your contribution + employer match). The calculator doesn't care where the money comes from; it just computes how the balance grows. If your contribution is $500/month and your employer adds another $250, enter $750 as the monthly contribution.
Does this account for inflation?
No, this gives a nominal result, meaning future dollars not adjusted for inflation. To plan in today's-dollars terms, subtract an estimated inflation rate (3% is a common assumption) from your rate of return. So if you expect 7% nominal returns and 3% inflation, enter 4% as the rate to see your goal expressed in today's purchasing power.
What if I can increase my monthly contribution over time?
This calculator assumes a constant monthly contribution. If you plan to ramp it up, say, with raises every year, your real timeline will be shorter than this estimate. As a workaround, run the calculator with your average expected monthly contribution across the timeframe, or break the timeline into segments and calculate each at the contribution level for that period.