How are you projecting savings growth when you factor in both contributions AND compound interest together?

Been thinking about this a lot lately. Most calculators I've found either do compound interest OR show contribution growth but not both together in a way that's useful for planning.

What I actually want to see is: if I put £X away every month at Y% AER, what does my balance look like at 1 year, 5 years, 20 years — with the interest compounding on top of the contributions as I go, not just on the starting balance.

Built something that does this as part of a budgeting app I've been making. You set your goal, current balance, AER, interest frequency and regular contributions, then drag a slider from 1 month to 20 years. Shows the balance split into contributions vs interest earned. Updates in real time.

Curious how others here are doing this kind of projection — are you using a spreadsheet, a specific calculator, something else? Always felt like this was a gap in the tools available.