Math
Interest Calculator
See what your money grows into with simple or compound interest. Add a monthly contribution to model a real savings habit.
FAQ
Simple vs compound? +
Simple = interest only on the original principal. Compound = interest on interest. The longer the time horizon, the bigger the gap.
What's a realistic rate? +
High-yield savings: 4–5%. S&P 500 historical: ~10% nominal, ~7% after inflation. Treasury bonds: ~4%.