Compound Interest Calculator
See what your savings become: starting amount, optional monthly deposits, rate and years — future value and total interest earned, in any currency.
Project your savings
Why compounding feels slow, then sudden
Compound interest pays you on your original money and on the interest you've already earned. The formula for a lump sum is FV = P × (1 + r/n)n×t — but the intuition is simpler: growth accelerates because the base keeps growing. 100,000 at 10% earns 10,000 in year one but over 25,900 in year ten. The famous rule of 72 estimates doubling time: 72 ÷ rate. At 8%, money doubles roughly every 9 years.
Monthly deposits are the quiet hero: each deposit starts compounding the day it lands, so over long periods regular saving usually beats a bigger starting amount. Run the calculator once with deposits and once without — the gap is the strongest argument for starting now, even small.
Frequently asked questions
What is compound interest?
Interest on your money plus interest on previous interest — growth that accelerates over time.
What is the rule of 72?
72 ÷ annual rate ≈ years to double. At 8%, about 9 years; at 12%, about 6.
How much difference do monthly deposits make?
Over long periods, usually more than the starting amount itself — every deposit compounds from day one.