Retirement Calculator

Use this retirement calculator to project your savings from today to retirement, estimate retirement spending with inflation, and see whether your money lasts to your chosen life expectancy. It also shows the monthly contribution needed to close a shortfall and a simple low/base/high sensitivity check.

How to use our Retirement Calculator

1. Enter your current age, planned retirement age, and life expectancy age.
2. Enter your current retirement savings (the total you have today across all retirement accounts).
3. Open Advanced options and pick a Contribution style: "Monthly amount" or "Percent of income".
4. If you choose "Monthly amount", enter your monthly contribution. If you choose "Percent of income", enter your current annual income and savings rate.
5. Pick a Retirement spending target style: percent of current income or a yearly dollar amount in today dollars.
6. Set your inflation rate and your expected investment return before and during retirement. These inputs are required.
7. If you expect Social Security or a pension, enter the monthly amount in today dollars and the age it starts.
8. Choose contribution timing and retirement spending timing (these change results slightly).
9. Click Calculate to see your projected balance at retirement (future dollars and today dollars), whether money lasts, and the required monthly contribution to meet the goal.
10. If Sensitivity check outputs is On, compare the low/base/high scenarios to see how much small changes in assumptions affect your plan.

Definitions

Today dollars (real dollars): Money measured in today’s purchasing power. A $60,000 per year goal in today dollars means you want the same buying power later, even though the number of dollars will be higher.

Future dollars (nominal dollars): Money in the dollars of that future year, not adjusted for inflation.

Inflation: The rate that prices rise over time, so the same basket of goods costs more later.

Investment return: How fast your savings grow (or shrink). The calculator uses an average percent per year and converts it to a monthly rate.

Other retirement income: Income that is not from your portfolio, like Social Security or a pension. Social Security timing depends on claiming age. [2]

Net portfolio withdrawal: The part of your retirement spending that must come from your savings after subtracting other income. It is never below 0 in this tool.

Withdrawal rate (first year): Net amount needed from savings in the first retirement year divided by savings at retirement. It is a risk signal, not a promise.

Life expectancy age: The age you want your plan to cover. Some plans also face required minimum distributions (RMDs), which can force withdrawals from certain accounts after a certain age. [3]

Methodology

Money units policy (today dollars vs future dollars)

This calculator treats your spending goal and other retirement income inputs as today dollars (today purchasing power). It converts them to future dollars for each future month using your inflation rate, then runs the projection in future dollars. It also converts key outputs back to today dollars so you can compare apples to apples.

future_value = today_value * (1 + inflation_rate)^(years)

balance_today_dollars = balance_nominal / (1 + inflation_rate)^(years_from_today)

Rates and compounding (annual to monthly)

Inputs like inflation and return are entered as percent per year. The calculator converts each annual rate to an equivalent monthly rate so the month-by-month simulation stays consistent.

rate_decimal = rate_percent / 100

monthly_rate = (1 + annual_rate)^(1/12) - 1

Pre-retirement savings projection (monthly steps)

The calculator simulates from your current age to your retirement age in months. Each month, your balance grows by the pre-retirement return and then adds your contribution (or adds it first if you select beginning-of-month timing).

balance[m+1] = balance[m] * (1 + r_m) + contribution[m]

If you choose "Percent of income", monthly contributions are based on your annual income for that year divided by 12, and income can grow each year if you provide an income growth rate.

income[year+1] = income[year] * (1 + income_growth_rate)

Retirement spending and other income (inflation-adjusted)

In retirement, the calculator builds a monthly spending amount for the first retirement month, then increases it with inflation each month. Other income is handled similarly, starting at the month that matches its start age. Social Security estimates and claiming-age choices can change the monthly amount and start timing. [2]

spend_nominal[month] = spend_nominal[first_ret_month] * (1 + inflation_monthly)^(month_index)

other_income_nominal[month] = other_income_nominal[start_month] * (1 + inflation_monthly)^(months_since_start)

Net portfolio withdrawal each month is spending minus other income, floored at 0 (no negative withdrawals and no reinvesting surplus in this version).

withdrawal[m] = max(0, spending[m] - other_income[m])

Retirement drawdown (monthly steps) and run-out age

During retirement months, the balance grows by the post-retirement return and then pays the net withdrawal (or pays first if you choose beginning-of-month spending timing). If a required withdrawal exceeds the available balance, the tool records the first unmet payment and reports its age. An exactly depleted balance is allowed if later spending is covered by other income.

balance[m+1] = (balance[m] * (1 + r_m)) - withdrawal[m]

Key outputs

Projected savings at retirement (future dollars) is the simulated balance at your retirement age. Projected savings at retirement (today dollars) discounts that balance by inflation back to today’s purchasing power.

First-year retirement spending and other income are summed over the first 12 retirement months and shown as annual amounts (and spending is also shown per month).

First-year net withdrawal rate is calculated only if savings at retirement is greater than 0.

withdrawal_rate = net_withdrawal_first_year / savings_at_retirement

Required monthly contribution (goal seek)

To estimate the required monthly contribution, the calculator uses a binary search: it tries different monthly contributions, re-runs the full projection, and finds the smallest contribution that covers every required retirement withdrawal through life expectancy. If the goal is not reachable within a high but finite cap, the required contribution is shown as N/A and you should consider retiring later, lowering spending, or adjusting assumptions carefully.

find contrib such that all retirement withdrawals are covered (binary search over contrib)

Sensitivity check (low, base, high)

If enabled, the calculator runs two extra scenarios to show how sensitive the plan is to small assumption changes. Low uses returns 1 percentage point lower and inflation 1 point higher. High uses returns 1 point higher and inflation 1 point lower. For the scenario definition only, inflation is capped at -2% to avoid extreme deflation assumptions. [1]

low: returns-1%, inflation+1%; high: returns+1%, inflation-1% (cap inflation at -2% for scenario only)

Sources