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Test · Calculator 08

Which assumptions change your financial future most?

Put returns, fees, inflation, earnings and property growth on a common visual scale, then test each assumption independently.

1 Enter your figures2 Review assumptions3 Explore the result

Your figures

1. Choose the time horizon
2. Add starting reference values

The three starting amounts are projected separately; they are not added into a net-worth total.

3. Set the assumptions

Move one control and watch both the trajectory and the sensitivity view respond.

Your entries remain in this tab and are cleared when the tab closes.

Starting investment after 20 years · today’s money

£73,239£120,010 in future pounds after the return and fee assumptions.
Property · today’s money£317,391£520,082 future pounds
Annual income · today’s money£49,600£81,275 future pounds
£100,000 cash purchasing power£61,027No cash interest modelled

A common starting line

Every line begins at 100. Values above 100 have grown faster than inflation; values below 100 have lost purchasing power. This makes unlike amounts comparable without pretending that income, property and investments are the same thing.

YearsInvestment after feesPropertyIncomeCash without interest
Hover over or focus a point to see its exact value.

One-point test

Which assumptions carry the result?

Each row changes only that assumption by one percentage point. Annual fees stop at 0% on the lower side.

Investment returnReal investment value
-17.4%+20.9%
Annual feeReal investment value
+10.5%-18.3%
Property-price changeReal property value
-17.9%+21.5%
Earnings growthReal annual income
-17.7%+21.3%
InflationPurchasing power of cash
+21.7%-17.6%
Assumptions used
  • Every rate remains constant for the selected horizon.
  • Investment return and the annual percentage fee are combined multiplicatively once a year.
  • Property value and annual income are shown separately and do not include debt, tax or spending.
  • Today-money values divide future pounds by the cumulative inflation assumption.
  • The lines are deterministic illustrations, not ranges, forecasts or probabilities.

The lab is designed to expose sensitivity, not to tell you which assumptions are likely or which asset to choose. Test values that are deliberately less comfortable as well as those you expect.