Investment inputs
Contribution timing
Monthly investing runway
Monthly Investment Calculator
Estimate how a starting balance and recurring monthly investment may grow over time. This calculator shows future value, total contributions, compound growth, inflation-adjusted value, and the monthly investment needed to reach a target balance.
Future value
$422,318
Projected account value.
Contributed
$190,000
Your deposited dollars.
Growth
$232,318
Return after fee drag.
Target gap
$77,682
Remaining distance to target.
Contribution vs growth split
The bar separates your own deposits from estimated compound growth.
55.0% growth
Contributions 45.0%Growth 55.0%
| Year | Contributed | Growth | Balance |
|---|---|---|---|
| 1 | $19,000 | $1,040 | $20,040 |
| 2 | $28,000 | $2,785 | $30,785 |
| 3 | $37,000 | $5,283 | $42,283 |
| 4 | $46,000 | $8,588 | $54,588 |
| 5 | $55,000 | $12,756 | $67,756 |
| 6 | $64,000 | $17,849 | $81,849 |
| 7 | $73,000 | $23,930 | $96,930 |
| 8 | $82,000 | $31,069 | $113,069 |
| 9 | $91,000 | $39,340 | $130,340 |
| 10 | $100,000 | $48,823 | $148,823 |
| 11 | $109,000 | $59,603 | $168,603 |
| 12 | $118,000 | $71,771 | $189,771 |
What Is a Monthly Investment Calculator?
A monthly investment calculator estimates how recurring deposits can build wealth over time. Instead of asking only what a lump sum may become, it models the habit that many investors actually use: adding money every month through an automated transfer, retirement contribution, or brokerage deposit. The result shows both your own contributions and the estimated growth from compounding.
This page is designed for planning, not prediction. Markets do not deliver the same return every month, and a real portfolio can have taxes, trading costs, account limits, and periods of loss. The calculator keeps those limits visible while still giving you a useful planning baseline for comparing contribution levels and time horizons.
How to Calculate Monthly Investment Growth
The calculator converts your annual return assumption into a monthly rate, subtracts the monthly fee drag, and then projects the balance one month at a time. If contributions are set to the beginning of the month, each monthly deposit is added before growth. If they are set to the end of the month, growth is applied first and the deposit is added afterward.
Balance after each month = prior balance x (1 + net monthly rate) + monthly investment
The inflation-adjusted value discounts the future balance back by your inflation assumption. The target monthly contribution uses the same projection engine and solves for the monthly amount that reaches your selected target value.
Worked Examples
Example 1: Starting small and investing consistently
A person who starts with $1,000 and invests $250 per month for 15 years may still build a meaningful account because the habit repeats 180 times. In the early years, most of the balance comes from deposits. Later, growth can become a larger share because prior growth also has time to compound.
Example 2: Raising the monthly contribution
Increasing a monthly investment from $750 to $1,000 changes every future month, not just the next deposit. That is why a small recurring increase can have a much bigger long-term effect than a one-time contribution of the same size.
Frequently Asked Questions
How does a monthly investment calculator work?
A monthly investment calculator projects a starting balance plus recurring monthly contributions over a selected time period. It applies an assumed annual return, converts it to a monthly rate, and estimates future value, total contributions, and growth.
What formula is used for monthly investing?
This page uses a month-by-month compound projection. Each month adds the contribution either before or after growth, applies the net monthly return, and repeats until the end of the term. This also supports fees, inflation, and a target monthly contribution estimate.
Should monthly contributions be added at the beginning or end of each month?
Beginning-of-month contributions have slightly more time to compound, so they usually produce a higher final value. End-of-month contributions are a conservative assumption because each contribution starts compounding one month later.
Does this calculator include inflation?
Yes. The main future value is shown in future dollars, and the real value card discounts the result by your inflation assumption. That makes it easier to compare future purchasing power with today's dollars.
Does this calculator include taxes?
No. It does not calculate capital gains tax, dividend tax, retirement account rules, tax-loss harvesting, or contribution limits. Treat it as a planning estimate and review tax-sensitive investment decisions with a qualified professional.
About This Calculator
Use this monthly investment calculator to estimate future value, contributions, compound growth, real value, and monthly investing needed for a target.
Frequently Asked Questions
How does a monthly investment calculator work?
A monthly investment calculator projects a starting balance plus recurring monthly contributions over a selected time period. It applies an assumed annual return, converts it to a monthly rate, and estimates future value, total contributions, and growth.
What formula is used for monthly investing?
This page uses a month-by-month compound projection. Each month adds the contribution either before or after growth, applies the net monthly return, and repeats until the end of the term.
Should monthly contributions be added at the beginning or end of each month?
Beginning-of-month contributions have slightly more time to compound, so they usually produce a higher final value. End-of-month contributions are a conservative assumption.
Does this calculator include inflation?
Yes. The main future value is shown in future dollars, and the real value card discounts the result by your inflation assumption. That helps compare future purchasing power with today's dollars.
Does this calculator include taxes?
No. It does not calculate capital gains tax, dividend tax, retirement account rules, tax-loss harvesting, or contribution limits. Treat it as a planning estimate.
What return should I enter?
Use a return assumption that matches the portfolio risk you are modeling. Returns are uncertain and can vary widely from year to year, so testing conservative and optimistic scenarios is useful.
Why is the target monthly investment different from my current monthly amount?
The target monthly estimate solves for the contribution needed to reach your target value using the same starting balance, return, fee, inflation, time horizon, and contribution timing assumptions.
Is this the same as an investment return calculator?
No. An investment return calculator often measures performance from known beginning and ending values. This monthly investment calculator focuses on recurring contributions and target planning.
AC
Alex ChenSenior Financial Analyst
Alex specializes in personal finance modeling with experience in investment analysis and tax optimization. He ensures every financial calculator follows current IRS guidelines and industry-standard formulas.
- CFA Level II Candidate
- B.S. in Finance, University of Michigan
- 8 years in financial planning tools