How a principal — plus regular top-ups — actually grows.

What's the difference between this and simple interest?

Compound growth adds earned interest back into the principal each period, so future interest is calculated on a larger base — that's what "compounding frequency" controls: maturity = P × (1 + r/n)^(n×t). More frequent compounding produces a slightly higher return at the same stated rate.

What does the monthly contribution field add?

It lets you model a lump sum that also receives regular top-ups — a hybrid between a one-time deposit and a pure SIP. If you're only ever adding money monthly with no starting lump sum, the dedicated SIP Calculator is a more natural fit.

How much does compounding frequency actually matter?

The difference shrinks the more frequent compounding already is — daily vs. monthly matters far less than monthly vs. annual, at the same stated rate. On $100,000 at 8% over 10 years, annual compounding yields about $215,900, while daily compounding yields about $222,500 — a modest but real difference.

Are these numbers guaranteed?

No — this is a projection based on a constant assumed rate you enter. Real investments and bank rates fluctuate, and past performance doesn't guarantee future results.