Retirement and savings goal planner

Monthly saving for a goal, future value after inflation, and how long savings last.

Compounded monthly. Use a rate you can actually expect after fees.

Deposit each month
499.19
Total deposited
69,902.80
Balance
100,000.90

Assumes a constant return and inflation every year, monthly compounding, no taxes or fees beyond what the rates include. Real returns vary from year to year, and the order of good and bad years matters in retirement. A projection, not advice.

What this tool does

Three questions about saving, each on its own tab:

  • Savings goal: how much you need to put aside each month to reach an amount by a date, or how long it takes at the amount you can afford.
  • Future value: what a starting sum plus monthly deposits grows to, year by year, with the result also shown in today's money after inflation, a chart and a table.
  • Retirement: a projection from your age now to retirement and beyond: savings at retirement, the first monthly withdrawal, and the age at which the money runs out at a given withdrawal rate or spending level.

The arithmetic is exact: amounts are kept in whole cents with no rounding between months, the same engine as our compound interest calculator. Everything is computed on this page.

How the numbers are worked out

  • The yearly return is split into 12 monthly periods (6% a year is 0.5% a month) and compounded monthly.
  • Deposits are monthly, at the end of each month unless you choose the start; a deposit at the start earns one more month of growth.
  • Monthly deposit for a goal solves the standard annuity formula exactly: deposit = (goal − savings × g) ÷ ((g − 1) ÷ i), where i is the monthly rate and g = (1 + i)^months. The answer is rounded up to the cent, so paying it always reaches the goal; the tests check that one cent less does not. Example: 100,000 in 10 years from 10,000 already saved, at 6%, needs 499.19 a month.
  • Time to a goal steps month by month until the balance reaches the goal: 500 a month at 5% passes 50,000 after 7 years (84 months), with 42,000 deposited and 8,164.33 of growth.
  • Today's money divides a future amount by (1 + inflation)^years. At 3% inflation, money in 35 years buys about 36% of what it buys today.

The retirement projection

From your current age to the retirement age, savings grow with your monthly saving at the return you expect before retiring. From retirement, money is withdrawn at the start of each month and the rest grows at the (usually lower) return you expect after retiring. Two ways to set the withdrawal:

  • A percentage of the savings: the first year takes that share of the balance at retirement, then the amount rises with inflation every year, whatever the markets do. This is how the often-quoted "4% rule" is defined, from US studies of historical returns; it is a rule of thumb, not a guarantee, and other countries' histories give lower safe rates.
  • A monthly amount in today's money: the amount you want to live on, raised by inflation until you retire and every year after.

Example with the default figures: age 30 to 65, 20,000 saved, 500 a month, 6% before and 4% after retiring, 3% inflation and a 4% withdrawal. Savings reach 874,826.18 at 65 (310,898.70 in today's money); the first withdrawal is 2,916.09 a month; the money lasts 29 years 4 months, to about age 94.

Assumptions, stated plainly

This is a projection, not advice. It assumes the same return and inflation every year; real markets move up and down, and in retirement the order of good and bad years matters: losses early in retirement, while you are withdrawing, do more damage than the same losses later. It ignores taxes, fees beyond what your rate includes, pensions and social insurance payments, and changes in spending. Try a pessimistic return and a higher inflation as well as your expected figures, and treat the range between them as the honest answer. The article on compound growth and inflation explains why.

Frequently asked questions

How much should I save each month to reach my goal?

Enter the goal, what you have saved, the expected return and the number of years. The tool solves the annuity formula exactly and rounds up, so that amount always gets there. 100,000 in 10 years from 10,000 at 6% needs 499.19 a month.

What is the 4% rule?

A rule of thumb from US research: withdraw 4% of your savings in the first year of retirement and raise the amount by inflation each year. In the US historical data it came from, that lasted at least 30 years with a mix of stocks and bonds. It is not a guarantee, and it depends on the investment mix and the country.

Why show results in today's money?

Because prices rise. At 3% inflation a million in 35 years buys what about 355,000 buys today. Planning with future numbers alone makes a goal look closer than it is.

Does it include taxes, fees or a state pension?

No. Use a return after fees, and subtract any pension income from the spending you need. The result is arithmetic on your assumptions, not financial advice.

Is the calculation exact?

Yes, within its assumptions: amounts are whole cents in exact integer arithmetic with no rounding between months, and the goal deposit is solved with exact fractions. The figures were checked against an independent Python script.

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Updated October 14, 2026 · More in Numbers