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This savings calculator shows how money grows over time with compound interest. Enter a starting deposit, an optional monthly contribution, the annual interest rate and the number of years, then choose how often interest is added. The final balance, your total contributions and the interest earned update as you type.
Compound interest is interest earned on both your original money and on the interest already added. Each period the balance grows a little, and the next period's interest is calculated on that larger balance — so savings grow faster the longer you leave them. This 'interest on interest' effect is what makes long-term saving so powerful.
Adding a fixed amount every month has an outsized effect because each contribution has its own time to compound. A modest monthly deposit, kept up for years, often ends up adding more to the final balance than the starting amount — the earlier and longer you save, the more each unit of money earns.
Interest can be added monthly, quarterly or yearly. The more often it compounds, the sooner earlier interest starts earning its own interest, so monthly compounding gives a slightly higher balance than yearly at the same rate. The gap is small over one year but adds up over decades.
It runs a month-by-month simulation: each month your contribution is added and one month of interest is applied, using the monthly equivalent of the compounding rate you choose. Figures are an estimate and assume a fixed rate; real accounts may vary with rate changes, fees and tax on the interest.
Start with $1,000, add $100 a month at 5% compounded monthly for 10 years. You contribute $13,000 in total, but the balance grows to about $17,240 — roughly $4,240 of it interest earned along the way.
For a fast estimate of how long money takes to double, divide 72 by the annual rate. At 6% a year, money doubles in roughly 72 ÷ 6 = 12 years; at 8%, in about 9. It is an approximation, but it shows why a couple of extra percentage points matter so much over a long time.
Interest earned on your original deposit and on the interest already added. Because each period's interest is calculated on a bigger balance, savings grow faster the longer you leave them.
Yes. Each month your contribution is added and then earns interest, from the first month through the last one in the term.
Match your account. Many savings accounts compound monthly; some bonds and deposits compound quarterly or yearly. More frequent compounding gives a slightly higher balance at the same rate.
It's before tax. Interest may be taxable depending on your country and account type, so your real take-home return can be a little lower.
No — it's an estimate that assumes a fixed rate for the whole term. Real rates can change, and fees reduce the balance, so treat it as a projection.