Compound Interest Calculator

Compound interest is interest that earns interest. In year one the growth comes only from your original balance; from then on, last year's interest joins the pile and starts generating returns of its own. The result is not a straight line but a curve that bends upward, and the bend gets steeper the longer you leave it alone.

Two levers matter far more than most people expect. The first is time. Because the curve compounds, money invested early does vastly more work than money invested later. Ten years of head start can outweigh a much larger monthly deposit started late. The second is the rate, but the rate is fragile — nobody can promise a return, and a difference of two percentage points compounds into a startling gap over decades.

Regular deposits smooth the ride. Adding a fixed amount each month means you buy more when prices are low and less when they are high, and it keeps the machine running even in months when markets wobble. A common mistake is to wait for the "right moment"; because the growth is exponential, the cost of waiting is measured in years of compounding you never get back.

This calculator assumes a constant rate and deposits at the end of each month. Real returns fluctuate, fees skim a slice, and inflation quietly erodes what the balance can buy. Use the estimate as a planning tool, not a promise: it shows the shape of the curve and the power of habit, which is the part you actually control. It is not financial advice, and you should confirm figures with a qualified adviser before acting.

This calculator returns estimates for general information only. It is not financial, investment, tax or legal advice, and it cannot replace guidance from a qualified professional who knows your circumstances. Figures such as loan payments, investment growth and retirement projections are simplified models based on the inputs and assumptions you provide, not guarantees of future results.