Investment Goal Calculator
Find how much to invest each month or year to reach a savings goal by a target date, given an assumed return and any amount you have already saved.
To reach an investment goal by a certain date, you work backward: your current savings grow on their own, and your regular contributions have to cover the rest. This calculator solves for the contribution you need each month or year to hit a target amount, given how long you have, the return you assume, and what you have already saved. It is the inverse of a growth projection, so the answer is the exact contribution that reaches the goal.
Assumptions
- The return is constant for the whole period and the number of years is treated as a whole number. Contributions are made at the end of each period; the per-period rate is the exact effective rate from the annual return, so a monthly or annual plan reconciles to the rate you enter.
- The amount already saved grows on its own at the same return. The required contribution solves for exactly the future value still needed after that growth, using the inverse of the standard annuity future-value formula, so contributing this amount reaches the goal precisely under the stated assumptions.
- If your current savings already grow to the goal or beyond, the required contribution is zero. Total growth is the goal minus your starting amount and total contributions; it can differ from a forward projection by rounding.
- All figures are nominal (not adjusted for inflation) and before taxes and fees. A real goal in today's dollars would need a larger nominal target, and taxes or fees would require contributing more.
- Not modeled: variable or negative returns and sequence-of-returns risk (one steady rate is used), fees, taxes, and any change to your contribution over time. Every result is rounded to the nearest cent.
- This is an estimate for educational purposes only, not financial advice. Real returns vary year to year, so treat the required contribution as a planning baseline, not a guarantee.
How it works
This solves a growth projection backward. Instead of asking what a contribution grows to, it asks what contribution is needed to reach a target.
First, any amount you have already saved grows on its own at the assumed return:
startingGrowsTo = starting times (1 + return)^years. Whatever that does not cover is the future value
your contributions must supply: remaining = target − startingGrowsTo, never less than zero.
The required contribution is the inverse of the annuity future-value formula. The future value of n
level contributions at a per-period rate r is contribution times ((1 + r)^n − 1) / r. Solving that
for the contribution gives:
contribution = remaining times r / ((1 + r)^n − 1)
where r is the effective rate per contribution period, (1 + return)^(1/k) − 1, and n is the number of
contributions. Because this is the exact inverse of the forward formula, contributing this amount
reaches the target precisely under the assumptions.
Worked example
Goal: $100,000 in 10 years at a 7 percent return, with $20,000 already saved, contributing monthly.
- The $20,000 grows to $20,000 times 1.07^10 = about $39,343.
- Remaining to fund with contributions: $100,000 − $39,343 = about $60,657.
- The annuity factor over 120 months at the effective monthly rate is about 173.085.
- Required monthly contribution: $60,657 divided by 173.085 = about $354.61.
With nothing saved, the same goal needs about $584.62 a month, so the head start cuts the required contribution by nearly 40 percent, because the early money has the longest to compound.
Scope and limitations
The return is assumed constant and the goal is in future, nominal dollars. Because assumed returns are uncertain, plan with a conservative return and treat a higher one as upside. For an inflation-adjusted target, estimate the future cost with the inflation calculator first. To project a fixed contribution forward instead, use the portfolio growth calculator. This is an estimate for education, not financial advice.
Sources
- U.S. SEC, Investor.gov: saving toward a goal and compound growth
- U.S. SEC, Investor.gov: investing basics
- Standard annuity future-value formula and its inverse (payment to reach a target future value).
Frequently asked questions
- How do I figure out how much to invest to reach a goal?
- You work backward from the goal. Any money you have already saved grows on its own, and your regular contributions must supply the rest. The math solves for the contribution that, compounded at your assumed return over the time you have, exactly reaches the target. This calculator does that and shows the monthly or annual amount.
- What if I have already saved some money?
- Enter it as the amount already saved. The calculator grows it at the same return and subtracts what it becomes from your goal, so you only need to contribute enough to cover the remaining gap. The more you have saved, and the longer it has to grow, the smaller your required contribution.
- Why does the required amount change so much with the return I assume?
- Because returns compound over time, so a higher assumed return does more of the work and lowers your required contribution, while a lower return raises it. Assumed returns are uncertain, so it is wise to plan with a conservative return and treat a higher one as upside, not something to count on.
- Is the goal in today's dollars or future dollars?
- Future, nominal dollars. The calculator does not adjust for inflation, so if your goal is a certain amount of buying power, the future target should be larger than today's figure. You can estimate the inflated target with the inflation calculator, then enter that here.
Related calculators
Learn how this works
New to this topic? Our companion guide explains it in plain language: How Much Should I Invest Each Month to Reach My Goal?
Last reviewed June 2026.