Loading rates…
Ctrl Alt Decidectrlaltdecide.com
Pick when you started saving. This replays real savings rates, stock market returns and inflation from then to the latest month.
Loading rates…
Ctrl Alt Decidectrlaltdecide.com
The same money goes in on both paths, on the same days.
| Savings account | S&P 500 |
|---|
This savings vs investing calculator replays cash vs investing with real rates and returns. Pick the year you started saving, any January from 2000 to 2025, and it follows the same money to the latest month down two paths: kept in cash earning real savings rates, or invested in the S&P 500 with dividends reinvested. It answers "what if I had invested in the S&P 500" with month-by-month history, not an assumed average.
Both paths get the same money on the same days: a starting sum at the start of January, then a monthly amount added at the end of each month, up to the month before the latest. Neither path costs more, so only where the money sits changes. The amounts are examples (£10,000 plus £200 a month in the UK, $10,000 plus $300 a month in the US), and you can type your own over both. You can also have the cash earn nothing or invest only half in stocks, and the table counts what you put in in today's money.
In the UK, cash earns the Bank of England's average one-year fixed-rate bond rate, applied month by month; a typical easy-access savings account paid less. Stock returns are converted to pounds at each month's exchange rate. Both paths are tax-free, as in a cash ISA and a stocks and shares ISA. In the US, cash earns the 3-month Treasury bill yield, which money market funds and high-yield savings accounts track, and both paths are tax-free, as in a Roth IRA. No fund fees are taken, and pensions, 401(k)s and tax outside those wrappers aren't modelled.
These use the calculator's starting figures for one UK case and one US case, and are refreshed when the data updates.
Had you invested £10,000 and then £200 a month in the S&P 500 from January 2015 instead of keeping it in savings, by August 2026 you'd be £78,370 better off investing: £123,104 in the S&P 500, against £44,734 in savings.
Had you invested $10,000 and then $300 a month in the S&P 500 from January 2015 instead of keeping it in savings, by August 2026 you'd be $92,753 better off investing: $154,862 in the S&P 500, against $62,109 in savings.
Pick UK or US and the year you started saving above, and type in what you had and what you added each month. The chart follows both paths to the latest month, and "How it played out" says how long investing trailed cash and its worst fall from a high, measured on monthly averages. Returns include reinvested dividends, with no fees and no tax.
The UK version treats both paths as tax-free, so it works as a cash ISA against a stocks and shares ISA holding an S&P 500 tracker. The cash rate is the Bank of England's average one-year fixed-rate bond rate, not any one provider's ISA. It doesn't apply the yearly ISA allowance, so a large starting sum is treated as if it all went in at once.
Choose US above. Cash earns the 3-month Treasury bill yield, which money market funds and high-yield savings accounts track; a typical bank savings account paid far less. The answer depends heavily on the start year: from January 2000, the invested path spent much of the 2000s behind cash.
The calculator can't say what suits you or what comes next. It shows what happened: the table's "Put in, in today's money" row scales each deposit up by how much prices have risen since, and its "Gain after inflation" row shows whether each path kept its buying power. Inflation is the ONS consumer price index in the UK and the BLS consumer price index in the US.
This replays the past rather than forecasting. Try several start years above: the gap between the paths, and the months investing spent behind, vary a lot with timing. "Half stocks" shows a middle path, half in the S&P 500 and half in cash, rebalanced every month.