Regular Investment Calculator

What $500 a month for 20 years is worth at 5%, 7% and 9%

Suppose you invest $500 a month for 20 years at an expected 7% annual return, starting from $0, contributing at the end of each month, with 3% inflation. Over 240 months you contribute $120,000, and the projected future value comes to about $260,000 — roughly $140,000 of growth. After 3% inflation, that headline figure is worth only about $144,000 in today's money, which is the number to judge a goal against, not the nominal $260,000. The return assumption matters more than almost anything else over 20 years: keeping everything else the same, a 5% return projects to about $206,000, while a 9% return projects to about $334,000 — a spread from one assumption alone, which is why comparing a conservative, base, and optimistic case beats trusting a single number.

Every projection splits the same two ways: what you actually contributed, and what growth added on top. Over long horizons growth can become the larger share, because the earliest contributions compound the longest — which is why starting sooner usually matters more than investing a bit more later. Check the inflation-adjusted (real) value alongside the nominal figure, since a large future balance buys less than it looks like once you account for rising prices over a multi-decade horizon. The scenario comparison and contribution-sensitivity chart let you see how much the outcome swings with a different return assumption or a different monthly amount, which matters more than the single headline number since returns are never actually constant.

So what the tool hands you is an estimate of how a fixed amount invested at regular intervals — usually monthly — could grow at an assumed rate of return: the projected future value, your total contributions, the estimated growth, and an inflation-adjusted value. It is an educational projection based on the figures you enter, not a forecast and not a guarantee. Investment returns are not guaranteed and can be negative. The smooth growth shown here assumes a constant return, which real markets do not deliver — actual results vary with market performance, fees, taxes, inflation, and timing. Read the figures as an illustration of how regular investing works, not as a promise of any outcome.

Where the closed-form formula stops and the yearly schedule takes over

The projection is built from the standard future-value-of-contributions formulas below. When inflation, fees, taxes, changing contributions, or contribution pauses are enabled, the calculator applies the projection step-by-step across the yearly schedule rather than relying on a single closed-form equation.

Three assumptions travel with that arithmetic. Contributions compound at a constant assumed rate, and the switch to the step-by-step schedule happens the moment inflation, fees, taxes, changing contributions, or pauses are enabled. Beginning-of-period contributions earn one extra period of growth compared with end-of-period contributions — the calculator applies the correct form based on your setting. And the inflation-adjusted (real) value divides the nominal projection by (1 + inflation)ⁿ to restate it in today’s purchasing power.

The year your returns start out-earning your own contributions

$500 a month at 7%, carried out to thirty years. The contribution never changes, so every extra year of growth is bought purely with time already served.

Growth first exceeds contributions in year 19 — $123,125 of growth against $114,000 paid in. Everything before that year is mostly you saving; everything after is mostly the plan working. The last five years alone add $204,950 to the balance for $30,000 of new money, which is the practical case for not interrupting a plan near the end of it.

The same $6,000 a year, paid monthly, quarterly, or once

Identical total contributed, identical 7% return, identical twenty years. The only variable is when in the year the money lands, and whether each payment goes in at the start or the end of its period.

Between the worst cell — once a year, in arrears — and the best, once a year in advance, there is $18,232 on the same $120,000 contributed: small against the balance, but free. The annual payer gains the most from moving early because each payment then waits a full year rather than being paid in arrears; a monthly payer has almost nothing to gain from the switch. The projection steps month by month, so a weekly plan is modelled as its monthly equivalent and lands on the monthly row.

The monthly contribution it takes to hold real value as inflation rises

The nominal projection is fixed at $260,463. Inflation does not change that figure; it changes what it buys. The last column solves the more useful question — the monthly contribution that would put the real value back at $260,463.

At 3% inflation the plan keeps 55% of its headline purchasing power, and matching the nominal target in real terms would take $903 a month rather than $500. That is the honest size of the inflation problem, and it is also why a step-up — raising the contribution each year — is usually a better answer than a single larger figure you cannot afford today. With inflation adjustment switched on, the calculator carries this real figure next to the nominal projection, so you can see roughly what the future balance is worth in today’s purchasing power — usually the better measure when planning against a future cost.

The 1% fee that takes $29,443 out of the same twenty-year plan

Every figure above assumes no charges at all. Attach a 1% annual platform or fund fee to the identical plan — $500 a month at 7% for twenty years — and the projected value falls from $260,463 to $231,020. That $29,443 gap is 21% of all the growth the plan produced, because a fee is not a flat deduction: it lowers the growth rate, so it compounds against you for as long as your contributions compound for you. Judge a fee against the growth it removes, never against the balance it is quoted on.

Fees and taxes are optional inputs in advanced mode. An annual platform or fund fee reduces the effective growth rate, and a simplified tax on growth can be applied each year or once at the end. Both are deliberately simplified estimates — real tax rules and investment costs vary by country, by account type, and over time, so confirm specifics with an official source or a qualified professional.

Those simplifications are the honest limitations of the tool. It estimates the compounding math of regular investing. It does not model:

• Country-specific tax rules on investment gains, dividends, or withdrawals
• Employer match calculations, contribution limits, and account-specific rules (401(k), IRA, pension, ISA)
• Highly volatile investments, where year-to-year swings dominate the outcome
• Active trading strategies and market timing
• Expense ratios and taxes that change over time

It also cannot run the schedule backwards: this page models regular deposits, not withdrawals. For regular withdrawals from an invested balance — the SWP (Systematic Withdrawal Plan) structure, or a retirement drawdown — use the Retirement Withdrawal Calculator, which handles scheduled withdrawals alongside ongoing investment returns.

SIP, dollar-cost averaging and a monthly 401(k) contribution are one calculation

SIP (Systematic Investment Plan) is the term used in India for investing a fixed amount on a schedule, and the underlying compounding math is identical to the monthly-investment or dollar-cost-averaging calculators used elsewhere — and to a regular ISA or 401(k) contribution. So this page works as a SIP calculator and as a global regular-investment calculator: SIP, dollar-cost averaging, and regular contributions are treated as the same compounding math, and no country-specific tax or account rule is applied unless you enter it yourself.

Currency is only a label on that arithmetic. Switch to GBP, INR, EUR, CAD, or AUD and every figure — including the schedule and the Excel export — displays in that currency, while the compounding underneath does not change.

What you are investing in works the same way. To model regular S&P 500 or stock investing, enter your own assumed annual return — a long-run S&P 500 average, for example — rather than relying on live prices, and the calculator projects growth from that assumption exactly as it would for any regular monthly investment.

Sources and methodology

This calculator applies a compounding model to the assumptions you enter; it does not fetch live prices or fund returns, so what is sourced below is the model itself and the published series you can check your assumptions against. Contributions do not guarantee a positive return. Links open in a new tab.

• Compound Interest Calculator - the compounding model published by the US securities regulator, including the option to add a regular monthly contribution, which is the future-value arithmetic this page appliesU.S. Securities and Exchange Commission (Investor.gov) · verified 2026-09-01
• Dollar cost averaging - the definition of the fixed-amount, fixed-interval investing pattern this calculator models (the same structure as an SIP)U.S. Securities and Exchange Commission (Investor.gov) · verified 2026-09-01
• Investor Bulletin: How Fees and Expenses Affect Your Investment Portfolio - the basis for treating fees as a compounding drag on the projection rather than a flat deductionU.S. Securities and Exchange Commission (SEC) · verified 2026-09-01
• Consumer Price Index - the measured inflation series to sanity-check the inflation rate behind the inflation-adjusted (real) valueU.S. Bureau of Labor Statistics (BLS) · verified 2026-09-01
• Save and invest - the regulator guidance on building a contribution habit and on why an assumed rate of return is not a promised oneU.S. Securities and Exchange Commission (Investor.gov) · verified 2026-09-01

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Read the guides

For how compounding works with regular deposits, worked through step by step, see How Compound Interest Works With Regular Contributions.

To weigh investing this amount as regular contributions against putting it in as a single lump sum, see SIP vs Lump Sum Investment Calculation: What the Numbers Actually Show.