Retirement & Investment Calculators

The projection runs in two phases: it accumulates current savings and monthly contributions to the retirement age at the before-retirement return, then draws a monthly income — escalated each year by the inflation input — at the during-retirement return, and reports how long the balance lasts. The full walkthrough, the drawdown mechanics, and the FAQ are on the dedicated Retirement Calculator page. The balance that feeds the savings field usually sits in more than one account; how a traditional 401(k), a Roth, and a taxable brokerage account differ, and how to project them together, is the subject of the guide 401(k), Roth IRA, and Taxable Accounts: How They Fit Together.

The accumulation half of the retirement projection on its own: a lump sum plus regular monthly contributions grow at an assumed return, with the result split between what was contributed and what growth added. The timing option decides whether each contribution earns growth in the month it arrives. For the full guide, see the dedicated Investment Calculator page.

What every calculator here computes

Nearly every tool on this site reduces to one expression, the future value of a series. A starting balance P grows by a monthly rate r — the annual return divided by twelve — over n months, and each level contribution PMT grows for the months remaining after it is made:

FV = P·(1+r)ⁿ + PMT·[((1+r)ⁿ − 1) / r]

The first term is the lump sum compounding on its own. The second is the annuity formula for a stream of equal deposits: the earliest contribution compounds for nearly the whole horizon, the last one for no months at all — it arrives at the end of the final month — and the bracket sums all of those partial growths at once. The Investment Calculator above evaluates exactly this expression. In the first worked example — $25,000 to start plus $400 a month at an assumed 6% return for 20 years, computed at build time by the same engine as the form — the balance reaches about $267,571. Of that, $121,000 is money that was deposited (the starting amount plus 240 monthly contributions) and $146,571 is growth.

Two details of the formula are visible in the calculator's options. At a 0% return the bracket would divide by zero, so the engine handles that case directly and the result is simple addition: the same deposits at 0% total exactly $121,000, the contributions and nothing else. Choosing start-of-month contributions multiplies the annuity term by (1 + r), because every deposit earns one extra month of growth; on the example inputs that lifts the balance to $268,496, a difference of about $924 — small next to what the horizon and the rate do.

The horizon does the most work of any input, and the shape of the curve explains why. Stopping the same example at 10 years gives about $111,037, with $38,037 of growth; the second decade then adds about $156,535, more than the first decade's entire balance, because by then growth is compounding on growth as well as on deposits. The Compound Interest Calculator isolates the lump-sum term and lets the compounding frequency vary from daily to annual using the general form FV = P·(1 + rate/m)^(m·t).

The conventions behind every number

Four conventions apply to every projection on the site, and they shape how any result reads. Monthly compounding: growth is applied twelve times a year at the annual rate divided by twelve, except on the Compound Interest and CD calculators, where the frequency is a choice, and on the Inflation Calculator and the savings-runway formula, which step annually. End-of-month contributions: a deposit is treated as arriving at the end of its month unless a start-of-month option is offered and selected. Nominal dollars: balances are future dollars, not today's purchasing power; entering a real (after-inflation) return instead of a nominal one is how the tools show a result in today's dollars. A single constant return: every projection applies one steady rate for the whole horizon. Real markets vary from year to year, and the models make no attempt to simulate that variation, which is the largest single reason to read any output as the shape of an outcome rather than a forecast. The methodology page documents each convention alongside the tests that lock the engine to reference figures.

The same equation, solved for the contribution

The Savings Goal Calculator runs the future-value expression backward. Given a target, a starting balance, an assumed return, and a deadline, it first grows the starting balance alone to see how much of the target compounding covers, then solves the annuity term for the level monthly deposit whose compounded value fills the remaining gap. In the second worked example — a $100,000 goal, $15,000 already saved, an assumed 5% return, 12 years — the starting balance grows to about $27,298 on its own, and closing the rest of the gap requires about $369.49 a month. If the starting balance alone would already pass the target, the tool reports a required contribution of zero rather than a negative number. This is the entry point of the chain: a target becomes a monthly figure, and that monthly figure is the contribution input every accumulation tool downstream expects.

Accumulate, then draw down

The Retirement Calculator at the top of this page joins the accumulation formula to a second model that has no closed form and is simulated month by month. In the drawdown phase, each month the balance is multiplied by (1 + r) at the during-retirement rate and the month's withdrawal is subtracted; every twelve months the withdrawal is multiplied by (1 + inflation), so the modeled spending keeps pace with the inflation input rather than staying flat in dollars. The loop stops when the balance reaches zero or after 80 years of retirement, whichever comes first; a depleted balance is reported as elapsed months, as years, and as an age. A balance still positive at the 80-year mark is reported as never exhausted rather than forced to a finite number.

The third worked example: age 40 retiring at 67, $60,000 saved, $800 a month contributed at an assumed 6% before retirement, then $3,500 a month withdrawn at an assumed 4% during retirement, with the withdrawal escalated by an assumed 2.5% a year. The 27-year accumulation builds a nest egg of about $947,202, of which $319,200 was deposited. The drawdown then lasts about 28.2 years, reaching zero around age 95.2.

Changing one input at a time shows what each part of the model does. With the inflation input left blank, the withdrawal stays at $3,500 in every year and the runway stretches from about 28.2 years to about 58.3, because a withdrawal that grows every year compounds against the balance just as growth does. Lowering spending to $3,000 a month with inflation off flips the result to never exhausted: the during-retirement growth on that nest egg covers the withdrawals, so the loop reaches its 80-year limit without finding a month in which the balance falls to zero. Turn the assumed 2.5% escalation back on at that lower spending and the result is finite again, about 34.3 years, because at this spending level the rising withdrawal overtakes the growth on the balance within the window. That is a property of these particular inputs, not of escalation itself: a withdrawal small enough relative to the growth on the balance can rise every year and still leave the balance positive at the end of the window. Cut the spending to $1,500 a month with the same 2.5% escalation and the engine reports this nest egg as never exhausted.

From a balance to an income figure

The Retirement Withdrawal Calculator answers the drawdown question from two other directions. The first is the initial-withdrawal-rate convention known as the 4% rule: the first-year withdrawal is a fixed percentage of the starting portfolio, and in later years the dollar amount, not the percentage, is adjusted for inflation. Applied to the nest egg from the retirement example, 4% is about $37,888 in the first year, or $3,157.34 a month. The rule is a heuristic from William Bengen's 1994 study, reinforced by the 1998 Trinity study, under which a first-year withdrawal of 4% of the starting portfolio, adjusted for inflation annually, historically survived every rolling 30-year U.S. period in the data studied. It is research on one stock/bond mix and one horizon, not a guarantee; the guide The 4% Rule: Where It Comes From and What It Assumes lays out where it strains.

The second direction is the savings runway, a closed-form annuity-depletion formula in real terms: spending W a year in today's dollars from a portfolio P earning a real return r lasts n = ln(W / (W − P·r)) / ln(1 + r) years when W exceeds P·r. The retirement example's $42,000 a year is 4.4% of its nest egg, above the 4% convention. A 4% nominal return under the example's assumed 2.5% inflation is a real return of about 1.5%, and at that rate the formula gives about 27.6 years — close to the 28.2 years the month-by-month simulation produced for the same inputs. The two models ask the same question in different units and escalate spending differently — the simulation holds the first year's withdrawal flat and steps it up every twelve months, while the runway formula treats spending as level in today's dollars from the first year — so the two figures agree only approximately, and neither is wrong.

The floor at RMD age

Past a statutory age, withdrawals from a traditional account stop being entirely a matter of strategy. Required minimum distributions from traditional accounts currently begin at 73 under the SECURE 2.0 Act, scheduled to rise to 75 starting in 2033, and the RMD Calculator computes the amount with one division: the prior December 31 balance divided by the Uniform Lifetime Table divisor for the age reached that year. The engine holds the table in one place, so the fifth worked example comes straight from it: a $650,000 balance at age 74 uses a divisor of 25.5, for a required distribution of about $25,490 — 3.9% of the balance. The same balance at age 85 uses a divisor of 16 and requires about $40,625, or 6.3%. Because the divisor shrinks each year of the table, the required percentage rises with age regardless of what the balance does. The distribution is a floor, not a plan; the mechanics, the shortfall penalty, and the Roth exemptions are in the guide RMD Rules, Explained: Age 73, the Formula, and the Penalty.

How the tools chain together

The directory in the sidebar is one sequence of models rather than a set of unrelated forms, and the output of each stage is the input the next one expects.

1. The atom. The Compound Interest Calculator is the lump-sum term by itself, at any compounding frequency. The CD Calculator is the same expression with a term, a rate, and the effective APY reported.
2. Add contributions. The Investment Calculator adds the annuity term. The Savings Goal Calculator runs it in reverse, turning a target into the monthly deposit.
3. Give the account a name. The Roth IRA Calculator is the accumulation formula with Roth framing. The 401(k) Calculator is simulated month by month instead, so salary growth and the employer-match cap can be applied as pay rises. The Retirement Planner runs a traditional, a Roth, and a taxable balance through the same arithmetic side by side and reports the pre-tax combined total.
4. Retire. The Retirement Calculator takes the accumulated balance and joins it to the month-by-month drawdown with inflation escalation.
5. Turn the balance into income. The Retirement Withdrawal Calculator reads a first-year figure off the balance under the 4% convention and computes the closed-form runway.
6. Meet the floor. The RMD Calculator applies the Uniform Lifetime Table once the statutory age arrives.

Three tools sit beside the chain rather than on it. The Inflation Calculator is the deflator: it converts an amount across years at a steady rate in both directions, which is the arithmetic behind reading any nominal balance in today's dollars. The Net Worth Calculator is the starting snapshot — assets minus liabilities, reported as it is even when negative. The Life Insurance Calculator uses the DIME method (Debts, Income replacement, Mortgage, Education) and shows the 10× income figure alongside it, labelled as the heuristic it is.

What the models leave out, and how to read the output

These are planning tools, not tax or investment engines. None of them model taxes, Social Security, pensions, investment fees, contribution or income limits, or the sequence-of-returns risk that comes from variable real-world returns. The retirement model has no lifespan input either: the age it reports is the month the arithmetic reaches zero, not an expectation about how long anyone lives. Where a tool has a specific omission of its own — the employer-match formula on the planner, the taxes a brokerage account pays along the way — its page states it.

Four misreadings account for most of the surprise a result can cause. Reading a nominal balance as purchasing power. A balance 27 years from now is stated in the dollars of that year; a real return, or the Inflation Calculator, puts it in today's terms. Reading "never exhausted" as a promise. It means the balance was still positive when the simulation reached its 80-year limit — usually because growth at the entered return covers the withdrawals, though a large balance drawn down slowly can also outlast the window. It is a statement about the inputs and the window, not about the market, and one that a different return or a small change in spending reverses. Reading the assumed return as a prediction. The rate is the input the projection was run at; the placeholder values in the forms are examples of the format, not recommendations, and every worked example on this page labels its rate as an assumption. Reading one run as the answer. Because the models are deterministic, the informative output is the difference between two runs — inflation on and off, a higher and a lower return — rather than either run on its own.

Guides

Four longer explainers cover the rules and research the calculators reference but do not model. 401(k), Roth IRA, and Taxable Accounts: How They Fit Together explains where in the timeline each account type is taxed and walks through projecting all three with the tools here. Retirement Age Milestones: 59½ to 73 lays out the statutory ages that structure retirement math and what each one changes. The 4% Rule: Where It Comes From and What It Assumes treats the rule as the research it is — Bengen's 1994 study and the 1998 Trinity study — and marks the boundaries of what the back-tests showed. RMD Rules, Explained: Age 73, the Formula, and the Penalty covers the start age, the divisor formula, the shortfall penalty, and the Roth exemptions. All of them are collected at Guides, and the ones that quote statutory figures state the date those figures were current.

Frequently asked questions

Not financial advice: these calculators provide general educational estimates that assume a constant rate of return and exclude taxes, fees, and market volatility. Actual results will differ — confirm consequential figures with a licensed financial professional. Everything is processed locally in your browser and never transmitted. How each calculator is built, tested, and verified is documented on the methodology page.