Intergrowth 21 Calculator
Use this calculator to estimate how your money could grow over time with compound returns and recurring contributions. It is designed around a 21-year horizon, but you can adjust the timeline.
What is the Intergrowth 21 calculator?
The Intergrowth 21 calculator is a long-term compounding tool focused on one simple question: what happens if I stay consistent for 21 years? It combines your starting balance, monthly investing habit, expected annual return, and contribution increases to project a future portfolio value.
Why 21 years? It is long enough to allow compounding to become meaningful, but still short enough to feel practical for real-life planning around career growth, family goals, and retirement preparation.
How this calculator works
Inputs you control
- Starting amount: Your current invested balance.
- Monthly contribution: The amount you add each month.
- Expected annual return: A planning estimate for average yearly growth.
- Years to grow: Default is 21 years, but adjustable.
- Annual contribution increase: Optional step-up to model raises or business growth.
- Inflation rate: Used to estimate purchasing-power adjusted value.
Outputs you get
- Projected portfolio balance at the end of the period
- Total amount you contributed over time
- Total growth from compounding
- Inflation-adjusted future value
- A yearly projection table for progress tracking
The math behind Intergrowth 21
This calculator uses monthly compounding. Every month, your balance grows by one month of expected return, then your new contribution is added. If you choose contribution growth, your monthly amount increases once per year.
In plain language: growth on top of growth + consistent deposits + time creates acceleration.
That is why small monthly habits can become large values over two decades, especially when contributions increase as income rises.
How to use this page effectively
1) Start with a realistic return assumption
Use conservative planning values. If you are unsure, run multiple scenarios (for example 5%, 7%, and 9%) and compare the range.
2) Model real contribution growth
If you can increase savings by just 1% to 3% per year, the long-term difference is often dramatic. This is one of the most underrated levers in wealth building.
3) Track progress annually
The yearly table helps you check if your actual savings behavior matches your target. Even if market returns vary, consistency in contributions can keep your plan on track.
Practical strategies to improve your 21-year outcome
- Automate monthly investing right after payday.
- Increase contributions whenever you get a raise.
- Avoid stopping contributions during volatile markets.
- Revisit assumptions once or twice per year.
- Focus on behavior first, forecasts second.
Frequently asked questions
Is this financial advice?
No. This is an educational projection tool. Actual returns are uncertain and can vary significantly year to year.
Can returns be negative?
Yes. You can enter a negative annual return (greater than -100%) to model stressed scenarios.
Why include inflation?
Nominal balances can look large in the future, but inflation reduces purchasing power. The inflation-adjusted value gives a more realistic sense of what your money may buy.
Should I always use 21 years?
Use 21 years as your baseline scenario, then test shorter and longer windows. Comparing timelines helps you understand the true value of starting earlier and staying consistent.