Before building Simple Interest Calculator, we looked at what "simple interest" actually means and what questions people ask about it beyond the basic formula.
Solve for principal simple interest, not just the balance
The formula (I = P × r × t) is simple, but the question you're actually asking isn't always "what's my balance?" Sometimes it's "what principal do I need to reach a target balance?" or "what rate got me from $1,000 to $1,150 in 3 years?" This tool solves for whichever of the four variables — balance, principal, rate, or time — you don't already know.
Simple interest vs compound interest: not the same math
Simple interest only ever applies to the original principal — it never compounds on previously earned interest. That's a real, different formula from our Compound Interest Calculator, not just a simplified version of it, which is why these live as two separate tools rather than one with a toggle.
Simple interest schedule csv, for the numbers you'd want to keep
Every mode generates a yearly schedule you can expand and download as CSV — interest and running balance for each year.
