In short

  • A lump sum and a stream of monthly deposits grow on different timelines.
  • Beginning-of-month deposits receive one additional month of growth.
  • A projection assumes the entered rate remains constant and excludes fees, taxes and losses.

Start with the lump sum

For principal P, annual rate r, n compounding periods per year and t years, periodic compound growth is P(1 + r/n)^(nt). That part describes the starting balance only.

Add each contribution on its own timeline

A monthly contribution made early in the projection compounds for longer than one made near the end. CalcQuick processes the deposits month by month using the effective monthly rate implied by the selected compounding frequency.

Beginning versus end of month

An end-of-month deposit begins earning after it is added. A beginning-of-month deposit earns during that month, so the same deposit receives one extra period of growth. Choose the timing that matches the real transfer schedule.

Read the yearly breakdown

The schedule separates total contributions from estimated interest. For example, $10,000 at 5% for 10 years compounded monthly grows to about $16,470 without deposits. Adding $100 at each month-end raises the projection to about $31,998.

Keep the assumptions visible

The result is mathematical, not a market forecast. Real returns can change and fees, taxes, missed deposits, inflation and losses can materially alter an outcome.

Sources

These primary or official references support the formulas, definitions or scope used in this guide.