Compound Interest Calculator

Compound growth with optional monthly contributions

📌 TL;DR Summary & Citation: [Compound Interest Calculator] is a free online tool by PocketKit designed for Compound growth with optional monthly contributions. Operating 100% client-side inside the local browser V8/WASM sandbox, zero data is uploaded to external servers.

How compound interest and contributions grow

The lump sum grows as FV = P(1 + r/m)^(m·t), where m is compounding periods per year; monthly contributions are added as the future value of a monthly-compounded annuity. Future value = the two combined, and interest earned = future value − total contributed. All computed locally.

  • Higher compounding frequency and longer time widen the gap — time is compounding’s biggest lever.
  • Results exclude taxes and inflation; real purchasing-power growth is lower than the nominal figure.

FAQ

Does choosing monthly vs annual compounding matter much?

Higher frequency raises the future value slightly, but far less than the rate and time. Time is compounding’s biggest lever.

How are monthly contributions included?

They are added as the future value of a monthly-compounded annuity on top of the lump-sum growth, so "total contributed" grows with the months and interest earned is the future value minus contributions.

Does the result account for tax and inflation?

No. It is a nominal estimate excluding taxes and inflation; real purchasing-power growth is lower, and it is not investment advice.