Savings growth predictor
Project regular monthly savings with compound interest, year-by-year balances, inflation-adjusted “real” wealth, and a side-by-side scenario if you bump contributions by 10%. No accounts, no servers—math only in your browser.
What this means
The table shows how fixed monthly deposits grow when interest compounds every month. The “real” column subtracts expected inflation so you can think in terms of what those dollars might buy compared to today—a rough guide, not a forecast from a central bank. Small changes in rate or time dominate long horizons: starting earlier and avoiding long gaps in contributions usually beats chasing an extra fraction of return.
The +10% scenario isolates one lever: earning a bit more, cutting a subscription, or automating a raise into savings. It compounds on top of the base plan—use it to sanity-check whether a modest lifestyle adjustment moves the needle you care about.
What you should do next
- Stress-test: rerun with rate ±2% to see sensitivity—long-term plans should survive boring markets.
- Match inflation to your country’s long-run CPI if you have a figure you trust more than the default.
- Pair with our loan and retirement tools so savings targets align with debt payoff order.
What-if scenarios
- Markets dip early — nominal balance paths wiggle; this model assumes a constant rate for planning, not trading.
- You skip three months — reduce total contributions manually in your head or rerun with a lower effective monthly average.
- Employer match — add match to monthly savings if it vests like cash; rules vary by plan.
Common mistakes
- Confusing nominal return with real wealth—especially over 20+ years.
- Using a savings account rate for stock-like expectations—or the reverse.
- Ignoring taxes on interest in taxable accounts (this tool does not model tax).
- Assuming “average” return each year; real paths are volatile even when long-run averages look smooth.
FAQ
What formula does this use?
Future value of an ordinary annuity with monthly compounding: FV = PMT × [((1 + r/12)^(12t) − 1) / (r/12)].
What is “real” balance?
Nominal balance divided by (1 + inflation) raised to the number of years—approximate purchasing power.
Why 0% rate still shows growth?
With 0% interest, growth is only from contributions: monthly × 12 × years.
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Disclaimer: Educational projection—not investment advice. Past performance does not guarantee future results.