Annuity, Perpetuity, and Time-Value Rules

Annuity and time-value rule pages cover compact formulas and shortcuts used to reason about repeated cash flows and long horizons.

These pages connect the core time-value idea to common valuation and planning calculations.

In this section

• Perpetuity: A Stream of Equal Cash Flows That Never Ends
  Learn what a perpetuity is, how the core perpetuity formula works, and why perpetuities matter in valuation even though real-world cash flows rarely last forever.
• Rule of 72
  An explanation of the Rule of 72, a quick way to estimate the time required for an investment to double at a fixed annual rate of interest.
• Time Value of Money: Why a Dollar Today Is Worth More Than a Dollar Tomorrow
  Learn the time value of money, the core finance principle behind present value, future value, discounting, compounding, and capital budgeting.