Long-term growth

Investment growth calculator

Investment growth should be read in two numbers: the future account balance and what that balance may buy after the inflation assumption.

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Live model

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Assumptions

template: investment_growth

initial_capital = 25000 in usd
monthly_investment = 800 in usd
return_rate = 7%
inflation_rate = 2%
compounds_per_year = 12
horizon_years = 20

Inputs

What the model needs

Initial capital: The invested balance at the start of the projection.
Monthly investment: Recurring contributions added throughout the horizon.
Return rate: The nominal annual growth assumption before inflation.
Inflation rate: The annual purchasing-power reduction.
Horizon: The number of years contributions and compounding continue.

Method

Formulas stay visible

future_value = compounded initial capital + future value of recurring contributionsreal_future_value = nominal_future_value / (1 + inflation_rate)^yearstotal_contributed = initial_capital + monthly_investment × 12 × years

The inputs and source use the same model. Open it in Continuum for a document you can keep and revisit.

Worked example

Twenty years of regular contributions

$25,000 starting capital
$800 monthly
7% nominal return
2% inflation
20 years

ResultWith monthly compounding, the projected balance is about $517,710, or $348,404 in today’s money. Total contributions are $217,000.

The nominal projection will be larger than its real value. Both matter: one describes the account statement, the other the modeled purchasing power.

Stress-test it

Compare a lower return with the same contribution schedule.
Change monthly contributions before chasing small rate improvements.
Extend and shorten the horizon to see the value of time.

Use it when

Comparing contribution plans
Separating nominal wealth from purchasing power
Testing how delay changes a long-term target

Know the boundary

Actual returns vary and do not arrive smoothly.
Fees, taxes, and allocation changes require additional assumptions.
The projection is educational and is not investment advice.

Questions

Why is real future value lower?

It discounts the projected balance by the inflation assumption, expressing the result in roughly today’s purchasing power.

Does the calculator assume returns every month?

The full Continuum template uses the stated compounding frequency. Real markets are uneven, so the smooth path is a planning simplification.

Should contributions rise with inflation?

This model keeps a fixed contribution unless you explicitly change it. A separate growing-contribution scenario can better represent rising income.

Keep the reasoning

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The full template opens as a local Continuum document. Edit every assumption, explore the result breakdown, and keep the source.

Open investment growth calculator

Investment growth calculator

What the model needs

Formulas stay visible

Stress-test it

Use it when

Know the boundary

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