What will your savings be worth in 20 years?
The headline balance is stated to the dollar and depends entirely on a rate nobody knows. Treat the rate as a range and you get the spread, plus what inflation quietly removes.
Personal Finance Intermediate Monte Carlo Pro engine
After you install, this is the model to open.
What Will the Savings Grow To, as a Range?
- In your spreadsheet, click the Sortia icon in the strip of icons down the right-hand edge. No strip? Click the arrow at the bottom-right to open it. You can also use Extensions, then Sortia, then Open Sortia.
- Click Start from a template and put that name in the search box.
- Pick the card with that name and click Load this template. It arrives on a new tab with real numbers already in it.
This one runs on a Pro engine, and every free install includes five full-quality runs on your own numbers, shared across all five Pro engines rather than five for each. After that, Pro is $199/year.
The answer
Across 20,000 futures:
- Nominal balance
- $616K mean
- Nominal P5 to P95
- $397K - $898K
- In today's money
- $357K mean
A fixed-rate calculator answers $621,895 to the dollar, which is the most misleading thing it does. The honest answer spans $397K to $898K, and in today's money it averages $357K, because twenty years of inflation removes roughly 40 percent of the headline. Note too that $240,000 of the balance is money you put in, not growth.
The model
$25,000 today, $1,000 a month, 20 years. Return runs 2 to 11 percent, inflation 1 to 5 percent.
| Starting amount | $25,000 |
| Monthly contribution | $1,000 |
| Horizon | 20 years |
| Return / inflation | ranges, not guesses |
Once it is in your sheet
- The model arrives with real numbers in it and runs as it stands, so you can press the button first and understand it second.
- Change the numbers to yours. The sheet marks which cells are inputs and which hold formulas, and most labels carry a note explaining the row.
- Press the run button at the bottom of the panel. It is labeled for the tool you are in, and the result lands on its own tab, with a written reading of it beside the figures.
Never used Google Sheets? Start here goes the whole way, in seven steps, and assumes nothing.
Next question
- Does buying ever win at big-city prices?Rent or Buy in an Expensive City
- Not whether a savings goal is hit: what one income-loss episode actually costs. This household can reach $11,000, which carries 65 in 100 episodes, and the 90 in 100 they asked for takes about $38,400.How Big Should the Emergency Fund Be?
- Pay a little extra each month. How much sooner is it gone?How Much Sooner Does an Extra Payment End the Loan?
- Will you actually hit your savings goal?Will You Hit Your Savings Goal?
- Will your retirement money last to 95?Retirement: Will the Money Last?
- Should you buy the house or keep renting?Rent vs Buy a House
Every model like this one, and the method behind them: Monte Carlo simulation.