Compound Interest Calculators

CompoundLab guides

Plain-language answers to compound interest calculators questions, written from the same sourced data behind CompoundLab. Every guide lists its sources and the date it was last updated.

• Updated June 10, 2026

  How accurate is the Rule of 72?

  How accurate is the Rule of 72 at different rates? Exact doubling times at 2%, 4%, 6%, 8%, and 12%, compared against the Rule.

• Updated June 10, 2026

  How much difference does compounding frequency actually make?

  How much does it matter if interest compounds annually, monthly, or daily? Computed example: $10,000 at 5% for 10 years.