How compounding makes money grow
Simple interest is paid only on your original deposit. Compound interest is different: each period’s interest is added back to the balance, so the next period earns interest on a slightly larger amount. Over time this snowballing effect — interest earning interest — is what makes long-term saving so powerful.
How often the interest is added matters. Compounding annually credits interest once a year; monthly or daily compounding credits it more frequently, so the balance grows a little faster. This calculator applies your chosen frequency across the full term and reports both the interest earned and the final balance.
Reading the charts
The growth line traces your balance year by year, so you can see how the curve steepens over time as compounding takes hold — growth that is gentle at first and accelerates later.
The donut chart splits the ending balance into your original principal and the interest it earned, making it easy to see how much of the final figure came from your deposit versus from growth.
Getting the most from compounding
A few principles amplify the effect:
- Time is the strongest lever — starting earlier matters more than contributing more later.
- A higher rate compounds on itself, so even a modest rate difference widens the gap over many years.
- More frequent compounding helps, but with diminishing returns; the jump from annual to monthly is larger than monthly to daily.
A note on assumptions
This model assumes a single deposit, a fixed rate and no withdrawals, additional contributions, taxes or fees. Real accounts may have variable rates and tax on earnings. Treat the result as an illustration of how compounding works rather than a guaranteed outcome.
Formula
ending = P·(1 + rate/100/m)^(m·years); interest = ending − PFrequently asked questions
- Does more frequent compounding earn much more?
- It helps, but with diminishing returns. Moving from annual to monthly compounding adds noticeably more than moving from monthly to daily.