Smart Money Calculator

Wealth planning

Wealth Growth Calculator

Model how a starting balance, monthly investing, extra contributions, annual return, and time horizon can affect long-term wealth.

Use this calculator to compare a base monthly investing plan with an extra monthly contribution. It estimates how the balance could compound over time using your chosen annual return assumption.

Inputs

Adjust the starting amount, monthly investing rate, return, and time horizon.

Results

Compare projected wealth with and without the extra monthly contribution.

Enter your assumptions and calculate to see the projected growth curve.

Assumptions

What this calculator assumes

These assumptions make the projection transparent and keep the limits of the model visible.

Growth model

Monthly compounding

The calculator converts the annual return assumption into a monthly rate and compounds balances once per month.

Contributions

End-of-month additions

Monthly and extra monthly contributions are added after each monthly growth step in the projection.

Return range

0% to 50% annual return

The return input is a modelling assumption, not a prediction. Real returns can be volatile and negative.

Time horizon

1 to 100 years

Long horizons make compounding easier to see, but very long projections become increasingly assumption-sensitive.

Tax and fees

Not included

The projection does not deduct platform fees, fund charges, taxes, inflation, or wrapper-specific limits.

Not advice

Scenario modelling only

Use this as a planning estimate and check product, tax, and regulated advice before making investment decisions.
Examples

Common wealth growth scenarios

Use these examples as starting points for thinking about contribution levels, time horizon, and return assumptions.

Building an investing habit

A saver starts with a modest balance and invests monthly.

  • Monthly contributions usually matter more than small return differences in the early years.
  • The chart helps show when compounding starts to become a larger part of the balance.
  • Testing a lower return assumption can make the plan more conservative.

Increasing contributions

A saver compares their current monthly investment with an extra contribution.

  • The extra contribution line shows the long-term effect of increasing the monthly amount.
  • This can be useful after a pay rise, debt payoff, bonus, or spending review.
  • The difference card keeps the incremental value visible without hiding the base plan.

Connecting to FIRE planning

A user tests whether their savings rate could support financial independence.

  • This page models portfolio growth, while a FIRE number calculator should model the target portfolio size.
  • Higher monthly contributions can matter more than chasing aggressive return assumptions.
  • Pension and ISA decisions should be considered alongside the raw growth projection.
FAQ

Wealth growth calculator questions

Important limitations

This calculator is for scenario modelling only. It does not account for inflation, volatility, taxes, investment fees, platform charges, wrapper limits, or personal financial circumstances. Check product documents, tax rules, and regulated advice before making investment decisions.