Investment Minimum Calculator
Minimum lump sum needed today to hit a target by a given year at a given return.
Calculate the minimum lump sum investment needed today to reach a future financial target by a set year at a given annual return rate.
What this tool does
This calculator determines the single upfront investment needed today to reach a specific financial target at a future date, based on an assumed annual return rate. It works backward from your goal—starting with the target amount, time horizon, and expected annual return—to show what lump sum must be invested now. The result represents present value, calculated using annual compounding with no additional contributions assumed after the initial investment. Time horizon and return rate are the primary drivers of the result; longer periods or higher returns reduce the lump sum required. This approach suits those planning a one-time investment rather than regular monthly contributions. The calculation is illustrative and assumes consistent returns; actual investment performance varies and past returns don't guarantee future results. For scenarios combining an initial lump sum with ongoing monthly savings, a different calculation method applies.
Enter Values
People also use
Investing
Present Value Calculator
Calculate the present value of a future cash flow at any discount rate and time horizon — what a future amount is worth in present terms.
Savings
Catch-Up Savings Calculator
The monthly contribution needed to reach a savings goal given what you already have, years remaining, and an expected return rate.
Investing
Return Needed Calculator
Work out the annual return you'd need to grow a lump sum to a target over a set number of years. Pure compound-rate math.
Formula Used
Spotted something off?
Calculations or display — let us know.
Disclaimer
Results are estimates for educational purposes only. They do not constitute financial advice. Consult a qualified professional before making financial decisions.
To reach 100,000 in 15 years at a 7% return, the minimum lump sum today is roughly 36,245. At 5% the minimum rises to about 48,102; at 9% it drops to 27,454. Small rate differences have large cash impact over 10+ year horizons.
What the result means
Primary is minimum lump sum. Secondary shows the compound growth that gets it to target, the multiple on the starting amount, and the growth rate applied. Compare to what you actually have today — the difference tells you how far off the mark you are.
When this matters
Windfalls (inheritance, bonus, property sale) force the question: invest now and forget, or spread it out? This tool calculates the lower bound — the minimum needed from that windfall to reach a specific goal. Anything above that provides a margin of safety.
Run it with sensible defaults
Using target amount of 100,000, years of 15 years, annual return of 7%, the calculation works out to 36,244.60. The defaults serve as a starting point.
The levers in this calculation
The inputs — Target Amount, Years, and Annual Return — do not pull with equal force. The rate and the time horizon typically 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.
How the math works
Present value of the target at the chosen return rate, annually compounded. Assumes no further contributions after the initial lump sum. For combined lump-sum-plus-monthly scenarios, use the Catch-Up Savings or Monthly Investment Goal tool.
Using this well
What this doesn't capture
Steady-rate math ignores real-world volatility. Actual returns are lumpy; sequence-of-returns risk matters most in drawdown; fees and taxes drag on compound growth; and behaviour changes in drawdowns can reduce outcomes below the projection. The number represents one scenario rather than a forecast.
To reach £100,000 in 15 years at 7 annual return, you need an initial investment of 36,244.60.
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 determines the initial lump sum needed today by computing the present value of your target amount. It divides the target by the compound growth factor over your chosen time period, using the annual return rate compounded annually. The model assumes a constant annual return throughout the holding period and that no additional contributions occur after the initial investment. It does not account for fees, taxes, inflation, or volatility in actual returns. For scenarios combining an initial lump sum with regular monthly contributions, refer to alternative tools designed for that purpose.
References
Frequently Asked Questions
What return rate is realistic?
What if I don't have the minimum?
Does this handle tax?
Is annually compounded realistic?
Related Calculators
Present Value Calculator
Calculate the present value of a future cash flow at any discount rate and time horizon — what a future amount is worth in present terms.
Catch-Up Savings Calculator
The monthly contribution needed to reach a savings goal given what you already have, years remaining, and an expected return rate.
Return Needed Calculator
Work out the annual return you'd need to grow a lump sum to a target over a set number of years. Pure compound-rate math.
More Investing Calculators
Investing
100 Minus Age Asset Allocation Calculator
Calculate stock-vs-bond allocation using the 100-minus-age rule of thumb — see the suggested percentage split for any age you put in.
Investing
Active vs Passive Investing Calculator
Compare active and passive investment strategies accounting for fees across long horizons — the wealth gap from a percentage point of fee drag.
Investing
Annuity Present Value Calculator
Calculate the present value of an ordinary annuity from regular payments, periodic rate, and the number of periods until the stream ends.
Investing
APR to APY Calculator
Convert APR to APY for any compounding frequency to see the true effective annual yield — what you actually earn (or pay) on a given quoted rate.
Investing
Art Investment Calculator
Calculate art investment net returns including insurance and carrying costs, given purchase price, current value, and length of holding period.
Investing
Asset Allocation Calculator
Calculate suggested portfolio asset allocation by age and risk tolerance (stocks/bonds/cash). Enter risk tolerance 1-10 to see suggested stock and bond.
Explore Other Financial Tools
Financial Health
Wealth Building Calculator
Project wealth building from current savings and ongoing contributions, given net worth, monthly contribution, and investment return.
Startup & VC
Exit Proceeds Calculator
Calculate net exit proceeds from ownership percentage, valuation, liquidation preferences ahead of you, and applicable tax.
SaaS & Subscription
Customer Lifetime Value Calculator
Calculate customer lifetime value using purchase value, frequency, lifespan, and gross margin to estimate total profit per customer over time.