A small, consistent return sounds unimpressive on its own. 1% a week doesn't feel like anything. But compounding is exactly what turns "unimpressive" into a genuinely large number over time — and understanding the actual math behind it is what separates realistic account planning from wishful thinking.
The compounding formula
Compounding just means each period's return is calculated on the new balance, not the original one. The formula is:
New balance = Old balance × (1 + return%) + any extra deposit
Run that same step over and over — daily, weekly, or monthly — and the growth curve stops being a straight line and starts curving upward, because you're earning returns on your previous returns, not just your starting capital.
A worked example
Start with $10,000 and a 2% return per week, no extra deposits, for 26 weeks (half a year):
- Week 1: $10,000 × 1.02 = $10,200
- Week 2: $10,200 × 1.02 = $10,404
- Week 10: $12,189.94
- Week 26: $16,734.18
That's a 67.3% total gain from a "small" 2% weekly return — because by week 26, you're no longer earning 2% of $10,000, you're earning 2% of whatever the account has grown to. This is the entire mechanism: constant percentage, growing base, accelerating absolute gains.
Adding regular contributions
If you add a fixed deposit every period on top of the trading return, growth comes from two sources at once: the compounding return on the existing balance, and the steady stack of new capital. Over a long enough horizon, consistent contributions can matter as much as the return rate itself — doubling your weekly deposit has a very predictable, linear effect, while doubling your return rate has an exponential one. Both matter, but they behave differently, which is worth separating out when you're planning rather than lumping "growth" into one number.
Where this model breaks down — on purpose
Every compounding projection assumes the return rate is fixed and repeats every single period. Real trading doesn't work that way. Some weeks you're up 5%, some weeks you're down 3%, and a string of losing weeks doesn't just pause the curve — it resets the base you're compounding from, which is a much bigger setback than a linear model suggests. A calculator projecting a smooth 2%-per-week line isn't a promise; it's a planning tool for "if I could sustain this average, here's the shape of the outcome."
This is also why prop firm evaluations and personal risk plans usually cap risk per trade as a fixed percentage rather than a fixed dollar amount — it's the same compounding logic working in reverse. A fixed percentage risk shrinks your position size as the account drops, which slows the descent, and grows it as the account climbs, which is exactly the mechanism above.
Model your own numbers
The math above is simple enough to sanity-check by hand for a few periods, but tracking it out further — especially with irregular contributions or comparing daily vs. weekly vs. monthly compounding — gets tedious fast. PipDesk's Compounding Calculator runs the full projection instantly and charts it, so you can see the curve for your actual numbers instead of estimating.