Investing · Calculator

Wealth multiplier.
What $1 invested today becomes at 65.

Every year of delay reduces what each dollar becomes at retirement. Enter your age and assumed return to see your personal multiplier and the cost of waiting one more year.

The question it answersWhat does a dollar invested today become by retirement?

Privacy: runs in your browser. What you enter stays on your device unless you copy a share link, which puts your inputs in the link.

Worked example: At age 25, $1 invested today becomes approximately $45 by age 65 at 10% nominal return: a 45x multiplier. At age 35, the same $1 becomes $17. Waiting 10 years costs roughly 28 multiplier points on every dollar. The arithmetic is identical at any return assumption; the multipliers compress at lower rates.

YOUR INPUTS
10% is the long-run S&P 500 nominal average. 7-8% is more conservative. Subtract 2-3% for inflationinflationA general increase in prices over time, meaning each dollar buys less than it did before.Full definition to estimate real purchasing powerPurchasing powerWhat money can actually buy, not the number on the bill or in the account. Inflation shrinks it over time: by the BLS consumer price index, it takes more than $8 today to buy what $1 bought in 1971. Same dollar, much less buying ability.Full definition.
RESULTS
YOUR MULTIPLIER
0x
Every $1 invested today becomes $0 by age 65.
START NOW
$0
START IN 1 YEAR
$0
COST OF WAITING ONE YEAR
$0
MULTIPLIER BY STARTING AGE

Projection, not a promise. The result follows the assumptions you enter. Real results will differ, sometimes by a lot.

How this tool works
  • Multiplier formula: (1+r)^n where r is the annual rate and n is years from current age to retirement age.
  • Future value of monthly investment: PMT × ((1+i)^(12n) - 1) / i, the standard ordinary-annuity formula, where i = (1+r)^(1/12) - 1 is the monthly rate that compounds to exactly r a year.
  • The "cost of waiting one year" is the difference between starting today and starting one year later, holding the monthly amount constant. Both balances are rounded to whole dollars before subtracting, so the three dollar figures always add up.
  • The tool shows a message and no results when the age, retirement age or return field is blank, when the retirement age is not later than the current age, or when the return is at or below -100%. A blank or negative monthly amount blanks only the dollar figures. In the age table, starting ages past the retirement age read "past retirement".
  • Returns shown are nominal (before inflation). Subtract 2-3% from your return assumption to estimate real purchasing power.
  • Past returns are not a guarantee of future performance. The S&P 500 has averaged roughly 10% nominal since 1928, but individual decade returns range from negative to over 17%.

Not financial advice. Calculator illustrates compound interestcompound interestEarning interest on your interest. Your returns reinvested to earn even more returns over time.Full definition math; past returns do not guarantee future results.

HOW THIS IS CALCULATED

This tool runs entirely in your browser: no data is sent to any server.

Years (n) = retirement age - current age. Rate (r) = the annual return you enter, 8% by default. No blank field is filled in for you: a blank age, retirement age or return, a retirement age not later than the current age, or a return at or below -100% shows a message instead of results, and a blank or negative monthly amount shows n/a for the dollar figures.

  • Multiplier = (1 + r)^n, compounded once a year. Shown to one decimal, and to cents in the sentence below it.
  • Start now = monthly amount × ((1 + i)^(12 × n) - 1) ÷ i, where i = (1 + r)^(1 ÷ 12) - 1: a deposit at the end of every month, growing at the monthly rate that compounds to exactly r over a year.
  • Start in 1 year = the same formula over n - 1 years to the same retirement age. Both balances round to whole dollars first, and cost of waiting = rounded start now - rounded start in 1 year, so the tiles subtract exactly.
  • The age table repeats the multiplier for starting ages 20 to 55 in steps of 5; a starting age above the retirement age shows "past retirement".

Both formulas use the same effective annual return: at 8%, the monthly rate is about 0.643%, not 8% ÷ 12 = 0.667% (which would compound to about 8.3% a year). The input hint's 10% figure matches the S&P 500's long-run record: $100 invested with dividends at the start of 1928 grew to $1,157,599 by the end of 2025 in NYU Stern's historical returns table, about 10.0% a year compounded[1]. The tool uses only the rate you enter. All results are nominal; taxes, fees and inflation are not deducted.

Verify the methodology or inspect the source code in your browser's dev tools.

Where to go from here

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Compound Interest

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Sources

Bracketed numbers in the text link to these sources. Figures, rates and rules change: check each source’s date before acting on it.

  1. NYU Stern (Aswath Damodaran), Historical Returns on Stocks, Bonds and Bills. Checked 2026-09-26. ↩

Calculators are educational estimates, not financial advice. Disclosures · How pages are reviewed