Compound interest calculator
Set a monthly contribution, a return and a horizon, and watch the curve bend. Free, no signup, and it shows you the thing most calculators hide.
Compounding Without compounding
You put in
£73,000
Growth
£179,111
Final
£252,111
Drag the years slider. Notice the curve barely lifts for a decade, then goes near vertical. That is why starting early matters more than the rate.
The thing most people get wrong
Most of the final number is built in the last third of the curve. Drag the years from 30 down to 20 and watch how much more than a third you lose. That is why starting early beats being clever, and why interrupting it is so expensive.
How to use it properly
- 1Set your realistic monthly contribution, not your aspirational one.
- 2Use a sober return. 7 to 8% is a reasonable long-run equity assumption before inflation. 15% is a fantasy.
- 3Then drag the years and watch what the last decade does. That is the whole lesson.
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