Imagine that instead of compounding the interest every day, you wanted to calculate it every nanosecond. And then, every billionth of a nanosecond. If you keep dividing that until it’s an infinite number of infinitely small compounding, you get a super simple equation:
interest = e^(years*rate)
10% interest for 5 years?
e^(5*.1) = 1.649
3% for 8 years?
e^(8*.03) = 1.271
You can plug any numbers into that and get the end result in 1 step.
Sibling’s explanation is a great starting point! If you understand annual, weekly, and daily compounding, continuous compounding is the limit of what happens when the time you compound over becomes ever shorter. It’s not obvious without calculus, but it’s a well-defined function.
Feedback: the compound interest calculator doesn’t support continual compounding? That’s surprising, and also the easiest to compute.