Investment Pot Growth Calculator
Investment pot projection.
Project investment pot growth from monthly contributions and an annual return rate to estimate future savings value over any time horizon.
What this tool does
This calculator projects the future value of a savings pot built through regular monthly contributions over a set time horizon, assuming a constant annual return rate. It models growth as the combined effect of your contributions plus earnings on the accumulated balance. The result shows what your pot might reach at the end of your chosen timeframe, expressed in your currency. Monthly contribution amount and time horizon are the primary drivers of final value, with expected return rate also shaping the outcome significantly. A typical scenario involves someone saving monthly for retirement, education funding, or another long-term goal. The calculation assumes contributions remain constant, returns are consistent, and no withdrawals occur during the period. Results are illustrative and based on the inputs you provide—actual outcomes may differ based on real market conditions and changes to contribution amounts.
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.
600/month for 30 years at 6.5%: final pot around 664,000. Of that, 216,000 is contributions; 464,000 is compound growth. Compound growth dominates contributions over long horizons — time in the market is the bigger lever than monthly amount past a point.
Quick example
With monthly contribution of 600 and horizon of 30 (plus expected return of 6.5%), the result is 663,706.85. 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 Monthly Contribution, Horizon, and Expected Return. 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
Future value of monthly annuity at monthly rate. 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 retirement pot size calculator, the lump sum investment calculator, and the pension 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.
Your investment pot of 663,706.85 assumes £600 monthly contributions over 30 years at 6.5 expected return.
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 future value of a series of monthly contributions using the standard annuity formula. It converts the annual expected return into a monthly rate, then applies that rate across the total number of months in your investment horizon. Each contribution is assumed to grow at the same constant monthly rate from the point it is deposited until the end of the period. The formula sums the compounded value of all contributions made throughout the timeline. The model assumes a constant return rate with no variation in performance across months or years, contributions made at regular monthly intervals, and no fees, taxes, or withdrawals during the investment period. It does not account for market volatility, changing return rates, or the sequence in which returns occur. Results should be treated as a projection based on the stated assumptions rather than a forecast of actual outcomes.
References
Frequently Asked Questions
Typical target pot?
Does 6.5% include inflation?
Pension vs taxable?
What if I can't afford this much?
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