Investment Calculator
Project the future value of a lump sum plus regular contributions.
- Author
- CentCompass
- Last Updated
- Reading Time
- 4 min read
Future value
$284,669.80
Total invested
$130,000.00
Total return
$154,669.80
| Year | Value | Invested | Return |
|---|---|---|---|
| 1 | $16,700.00 | $16,000.00 | $700.00 |
| 2 | $23,869.00 | $22,000.00 | $1,869.00 |
| 3 | $31,539.83 | $28,000.00 | $3,539.83 |
| 4 | $39,747.62 | $34,000.00 | $5,747.62 |
| 5 | $48,529.95 | $40,000.00 | $8,529.95 |
| 6 | $57,927.05 | $46,000.00 | $11,927.05 |
| 7 | $67,981.94 | $52,000.00 | $15,981.94 |
| 8 | $78,740.68 | $58,000.00 | $20,740.68 |
| 9 | $90,252.52 | $64,000.00 | $26,252.52 |
| 10 | $102,570.20 | $70,000.00 | $32,570.20 |
| 11 | $115,750.12 | $76,000.00 | $39,750.12 |
| 12 | $129,852.62 | $82,000.00 | $47,852.62 |
| 13 | $144,942.31 | $88,000.00 | $56,942.31 |
| 14 | $161,088.27 | $94,000.00 | $67,088.27 |
| 15 | $178,364.45 | $100,000.00 | $78,364.45 |
| 16 | $196,849.96 | $106,000.00 | $90,849.96 |
| 17 | $216,629.46 | $112,000.00 | $104,629.46 |
| 18 | $237,793.52 | $118,000.00 | $119,793.52 |
| 19 | $260,439.06 | $124,000.00 | $136,439.06 |
| 20 | $284,669.80 | $130,000.00 | $154,669.80 |
What is the Investment Calculator?
An investment calculator projects the future value of an initial lump sum combined with ongoing contributions, growing at an expected annual rate of return. It is the same compounding mathematics used for savings, applied to an assumed investment return rather than a contractual interest rate — which makes the output a scenario to reason about rather than a promise.
How the calculation works
The starting amount grows at the assumed annual return for the full period. Each contribution is added and then compounds for however many years remain, so early contributions do far more work than late ones. The calculator reports the ending balance alongside the total you contributed, and the difference between them is the portion generated by growth — usually the more revealing of the two numbers.
The formula
Future value combines two components. The lump sum grows as FV = P(1 + r)^t, where P is the initial amount, r the annual return as a decimal, and t the number of years. Recurring contributions follow the future value of an annuity: PMT · [((1 + r)^t − 1) / r]. Adding them gives the projected balance. Total contributed is P + (PMT × t), and growth is simply the projected balance minus that figure.
Worked example
Investing $10,000 up front plus $6,000 a year at 7% for 20 years projects to roughly $300,000. Contributions account for about $130,000 of that — the initial $10,000 plus twenty annual deposits — leaving roughly $170,000 from growth. Growth overtakes contributions somewhere around year fourteen, and the final five years add more to the balance than the first ten did, which is the clearest illustration of why an early start outperforms a larger late contribution.
Tips
- Reinvesting dividends and distributions is what drives the long-run curve.
- Diversify broadly rather than reaching for return in a single holding.
- Revisit your assumed return periodically — a long-run average is not a yearly guarantee.
- Watch expense ratios; a percentage point of fees compounds against you for decades.
- Automate contributions so the plan survives your attention and market moods.
Common mistakes
- Treating a projection as a forecast, when real returns arrive unevenly and can be negative for years.
- Assuming an optimistic return and building a plan with no margin for a worse outcome.
- Reading nominal results as real spending power and ignoring inflation.
- Forgetting fees and taxes, which quietly reduce the compounding rate.
- Stopping contributions during downturns, which removes the cheapest units you will ever buy.
Limitations
The model applies a single constant return every year, which no real portfolio delivers — the order and volatility of returns matter, especially if you withdraw money. Results are pre-tax, pre-fee, and nominal, so they overstate both the balance and its purchasing power. This is not investment advice and says nothing about whether a given return assumption suits your risk tolerance or time horizon.
Frequently asked questions
What return should I assume?
Many long-term plans model something in the range of 6–8% nominal for a diversified stock portfolio, based on multi-decade historical averages. Actual returns vary enormously year to year, and past averages are context rather than a guarantee.
Lump sum vs regular contributions?
Investing a lump sum earlier gives it more time to compound, which historically tends to win. Regular contributions spread the entry point over time, which reduces the risk of committing everything just before a downturn and is easier to sustain from income.
Is this after taxes?
No. Results are pre-tax and pre-fee. Whether you owe tax on growth depends on the account: taxable brokerage accounts are taxed on dividends and realised gains, while retirement accounts defer or eliminate that tax.
Why does growth accelerate later?
Because each year's return is calculated on a larger balance. A 7% return on a small early balance is a small number in dollars; the same percentage on a mature balance is many times bigger, so most of the total growth appears in the final years.
How is this different from a compound interest calculator?
The mathematics is identical. The difference is interpretation: interest is contractual and predictable, while an investment return is an assumption about uncertain markets. Treat this output as a scenario rather than a schedule.
How do fees affect the outcome?
Fees reduce your effective return every single year, so they compound against you. A fund charging one percentage point more than an alternative can consume a meaningful share of the final balance over a multi-decade horizon.
How do I calculate return on investment?
ROI is (final value − initial cost) ÷ initial cost, expressed as a percentage. It ignores time, so for multi-year comparisons an annualised figure is more useful than raw ROI.
How do I reduce risk while still earning a return?
Diversification across asset classes, geographies, and holdings reduces the impact of any single failure, and matching your asset mix to your time horizon reduces the chance of needing money during a downturn. Risk cannot be eliminated, only managed.
What is the difference between nominal and real return?
Nominal return is the raw percentage gain; real return subtracts inflation and describes actual purchasing power. A 7% nominal return during 3% inflation is roughly a 4% real return, which is the figure that matters for long-range planning.
Which account type should I invest through?
Tax-advantaged accounts such as a 401(k) or IRA generally come first because deferring tax raises the effective compounding rate, with taxable brokerage accounts used beyond those limits. The right mix depends on your income, employer plan, and time horizon.
Related calculators
Related guides
Sources
- SEC — Ten Things to Consider Before You Make Investing Decisions
- FINRA — Investing
- Investor.gov (SEC) — Save and Invest
How this page is produced
Editorial process. CentCompass is maintained independently, and this page is written and checked against the official publications listed above before it goes live. There is no separate editorial reviewer. This page was last checked on . See our editorial policy.
How the calculations work. Every result comes from a small, unit-tested calculation engine rather than a spreadsheet or a hardcoded table. Loans use the standard amortization formula, growth uses compound-interest math, income tax applies the federal progressive brackets, and payroll applies Social Security and Medicare rules. Our methodology sets out each one.
Where the figures come from. Tax brackets, standard deductions, FICA parameters, and contribution limits are stored once in a dated registry and read directly by the calculators — the same values appear in the text above, so the two can never drift apart. Each figure records its source, effective tax year, and review status on our data sources page.
Update policy. Regulatory figures are checked against their primary source when the IRS, SSA, or another authority publishes new values — typically each autumn for the following tax year — and again at the scheduled review date recorded for each dataset. Figures that have not been checked yet are marked as draft on the data sources page until that check is complete.
Educational purposes only — not financial, tax, or investment advice (disclaimer).