Savings and Compound Interest

Features

• Compound growth using (1 + r/n)^(n·t) with the chosen frequency, continuous included
• Monthly contributions grown at the equivalent monthly rate, with contributions kept distinct from compounding
• Goal mode: the monthly contribution still needed
• Inflation adjustment: the future nominal amount in today’s purchasing power
• A year table with one row every five years plus the last, not every year
• ⚠️ A zero return takes an additive branch, so it never divides by zero or yields NaN
• ⚠️ The result states this is arithmetic, not investment advice, and excludes tax
• Runs entirely in your browser

How to use

1. Choose a mode (compound, contributions, goal, inflation, deposit)
2. Enter the starting or target amount
3. Set the annual return, years and compounding frequency; add the monthly contribution in contribution mode
4. The result gives the future value, total contributed, earnings, year table and inflation adjustment

FAQ

How much does the compounding frequency matter?

Quite a bit. At 5% a year, annual compounding over ten years gives 1.05^10 ≈ 1.629, while monthly gives (1 + 0.05/12)^120 ≈ 1.647 — about 1.8% more over the decade. The longer the horizon and the higher the rate, the wider the gap. That is why the frequency is really substituted into the formula here.

Are monthly contributions the same as monthly compounding?

No. A contribution is money paid in each month (a cash flow); the frequency is how interest rolls up (a rate convention). They combine freely. Each contribution here grows at the equivalent monthly rate implied by the chosen frequency, paid at the end of each period, and the result says so.

What happens at a 0% return?

Nothing breaks. The term ((1+i)^n − 1) / i has a zero denominator when i is zero, so that branch adds instead: principal plus contribution times the number of periods. A 0% deposit is listed as it is, not as NaN.

Is this investment advice?

No. The rate is an assumption you enter, and the tool only does arithmetic. Real returns fluctuate, are taxed and are eroded by inflation; no tax is included here and the future is not predicted. Treat it as a “what if the assumptions change” calculator.