Subscription to Investment Calculator
Future value of redirecting a monthly subscription into investments instead.
Calculate how much a cancelled subscription could grow by redirecting the monthly cost into investments over time at a chosen return rate.
What this tool does
This calculator models the future value that accumulates when a recurring monthly subscription amount is redirected into an investment account over a set period. It takes three inputs—your monthly subscription amount, an assumed annual return rate, and the number of years—and estimates what that redirected money could grow to through compound growth. The calculation assumes monthly contributions made at the end of each month, compounding at the specified annual return rate. The result shows a projection based on consistent investing of the same monthly figure across your chosen timeframe. This illustration does not account for taxes, fees, inflation, or variations in actual returns, which typically differ from flat-rate assumptions. The output is educational and demonstrates the potential magnitude of opportunity cost associated with ongoing subscription spending.
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.
15 a month cancelled and invested at 7% for 30 years grows to roughly 18,300. That single 15 decision compounded across a career is meaningful money. Most households have two or three unused subscriptions — the combined FV tends to be surprising once calculated.
How to use it
Enter the monthly subscription cost, an expected annual return, and your horizon. The tool projects the future value assuming the monthly amount is invested each month instead.
Use it for auditing
Run the tool for each questionable subscription. Anything over 10/month that you don't actively use compounds into a surprising figure. The decision isn't about the 10 — it's about the FV that 10 quietly represents.
A worked example
With the defaults: monthly subscription of 15, annual return of 7%, years of 30 years. The tool returns 18,299.56. You can adjust any input and the result updates as you type — no submit button, no reload. That's the real power here: seeing how sensitive the output is to one or two assumptions.
What moves the number most
The result responds to Monthly Subscription, Annual Return, and Years. 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.
The formula behind this
Ordinary annuity future value with monthly compounding. Assumes the monthly amount is invested at the end of each month — standard approximation for regular investing. Everything the calculator does is shown in the formula box below, so you can check the math against your own spreadsheet if you want.
Why the behavioural angle matters
Most personal finance mistakes are behavioural, not mathematical. You know the math; the hard part is acting on it consistently. Calculators like this one are useful because they externalise a private feeling into a public number — and public numbers are easier to argue with than vague feelings.
What this doesn't capture
Behaviour-adjacent math is always an approximation. Human habits are lumpy and context-dependent; the figure here assumes steady behaviour which is a simplification. The output is a prompt for thinking rather than a precise prediction.
Redirecting £15 monthly over 30 years at 7 annual return grows to $18,299.56.
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 regular monthly investments using the ordinary annuity formula with monthly compounding. It converts the annual return percentage into a monthly rate, then applies the compound growth formula across the total number of months. Each monthly payment is assumed to be invested at the end of that month and grows at a constant monthly rate for the remaining period. The model treats all returns as reinvested and assumes a steady, uninterrupted contribution schedule. It does not account for fees, taxes, inflation, variable market returns, or changes to the subscription amount or return rate over time. Results represent a theoretical endpoint based on consistent conditions throughout the investment period.
Frequently Asked Questions
Is this realistic?
What return rate?
Multiple subscriptions?
Does this account for subscription price rises?
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