Cash vs Invest Calculator
Long-term cost of holding cash vs investing.
Compare long-term value of holding cash vs investing the same amount at expected market returns. Enter cash rate and investment return to see opportunity cost.
What this tool does
This calculator models the numerical difference between holding a lump sum in cash versus investing it over a set timeframe. It compounds your starting amount at both a cash interest rate and an expected investment return rate, then shows the gap between the two final values. The result illustrates what the difference in growth looks like in your currency at the end of your chosen horizon. The gap widens or narrows based primarily on the spread between your cash rate and investment return, combined with how long you hold the money. For example, someone comparing a savings account to a stock portfolio over ten years would see how different growth paths diverge. The calculator assumes consistent rates throughout the period and does not account for taxes, fees, inflation, or actual market volatility — it is a simplified illustration for educational purposes only.
Enter Values
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Formula Used
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Disclaimer
Results are estimates for educational purposes only. They do not constitute financial advice. Consult a qualified professional before making financial decisions.
50,000 held as cash at 3% vs invested at 7% over 20 years: cash grows to 90,306; investment to 193,484. Opportunity cost of cash: 103,178. Some cash buffer is necessary; too much costs real long-term wealth.
Quick example
With amount of 50,000 and cash rate of 3% (plus investment return of 7% and horizon of 20), the result is 103,178.66. Change any figure and watch the output shift — it's often more useful to see the pattern than to memorise the formula.
Which inputs matter most
You enter Amount, Cash Rate, Investment Return, and Horizon. The rate and the time horizon usually dominate — compounding means a small change in either reshapes the final figure more than a similar shift in contribution size. Test this by doubling one input at a time.
What's happening under the hood
Compound growth at each rate, subtract. The formula is listed in full below. If the number looks off, you can retrace the calculation by hand — that's the point of showing the working.
Why the number matters
Saving without a target is like driving without a destination — you'll make progress, but you won't know when you've arrived. This tool gives you a concrete figure to work toward, which is the first step in turning a vague intention into an actual plan.
What this doesn't capture
The calculation assumes a steady savings rate and a stable interest rate. Real saving journeys include emergencies, windfalls, and rate changes — especially in easy-access products. The figure is a direction of travel, not a guarantee.
Where to go next
This calculation rarely sits alone in a planning exercise. If you're running these numbers, you'll probably also want the compound interest calculator, the emergency fund calculator, and the short vs long term savings calculator — each one answers a different question in the same territory. Treating them as a set rather than in isolation usually produces a more honest picture.
Investing £50,000 at 7 return over 20 years grows to 103,178.66, compared to holding cash at 3.
Inputs
This example uses typical values for illustration. Adjust the inputs above to match a specific situation and see how the result changes.
Sources & Methodology
Methodology
The calculator computes the difference in growth between two parallel investments over your chosen time horizon. It applies compound interest to your initial amount using two separate annual rates: one for cash savings and one for investment returns. The formula calculates the future value under each scenario independently, then subtracts the cash outcome from the investment outcome to derive the gap. The model assumes constant annual rates of return, annual compounding, and makes no adjustments for fees, taxes, or inflation. It treats both scenarios as if the full amount remains invested or held for the entire period without withdrawals. The result models the nominal difference only and does not account for market volatility, sequence-of-returns risk, or how actual investment performance may vary year to year.
References
Frequently Asked Questions
How much cash is too much?
Does inflation change things?
What about tax-free accounts?
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