Most growth projections show you one big number and stop. That hides the most useful fact in the whole calculation: how much of the final balance is money you deposited, and how much is compounding doing the work.
Our new compound interest calculator puts all three numbers next to each other — future value, total contributed, and interest earned — and recalculates instantly as you drag your assumptions around.
A taste of why the split matters: $10,000 up front plus $200 a month at 7% for 20 years projects to about $144,573. You only deposited $58,000 of that; the other $86,573 is compounding. Add five more years and the balance jumps past $219,268 — for just $12,000 of extra deposits.
Everything runs in your browser, your inputs live in the URL so a result can be shared as a link, and the compounding assumptions (monthly, contributions at month-end) are stated plainly on the page.
Writing about saving or investing? The calculator is embeddable on your own site with a single iframe.