📈 Compound Interest Calculator
See what consistent saving actually becomes.
Assumes monthly compounding and a constant return. Real returns vary — this is an illustration, not a prediction.
Common questions
How is compound interest calculated?
Compound interest is calculated on your original principal plus all the interest already earned. The standard formula is A = P(1 + r/n)^(nt), where P is the starting amount, r the annual rate, n the number of compounding periods per year, and t the number of years. The practical consequence is that growth accelerates: the same rate produces far more in year 20 than in year 2.
What is the rule of 72?
Divide 72 by your annual return to estimate how many years your money takes to double. At 6% a year, money doubles in roughly 12 years; at 9%, in about 8. It is an approximation, not a formula, but it is accurate enough between about 4% and 12% to be genuinely useful for quick mental checks.
Does compounding frequency actually matter?
Less than most people expect. On RM10,000 at 5% over 10 years, annual compounding gives about RM16,289 and monthly compounding about RM16,470 — a difference of roughly 1%. The rate, the amount you contribute, and the number of years all matter far more than whether interest is credited monthly or yearly.
Is this calculator free to use?
Yes. Every CashDir calculator is free, requires no account, and runs entirely in your browser — the numbers you type are never sent to our servers or stored.