Lump sum or steady stream?
DCA means investing the same amount on a regular schedule. The calculator simulates yearly market swings around your chosen average return, so you can see how the two approaches compare in a wobbly world.
Volatility is how much returns swing year to year. The S&P 500 has historically averaged around 15–20% standard deviation. Educational simulation only.
Lump sum tends to win when markets rise consistently. DCA tends to shine in choppy or falling markets, and almost always wins psychologically — because most people don't have a lump sum, they have a paycheck.
A few notes
The simulation is deterministic — same inputs produce the same numbers — so you can compare scenarios without chasing randomness. In reality, sequence matters: a bad first decade with DCA can produce better long-run results than a great first decade with a lump sum.
The honest framing: most people don't have a lump sum. They have a paycheck. DCA is what happens automatically when you contribute to a 401(k) every two weeks. That's its real power — discipline, not math.
Read the lesson: Dollar-cost averaging — the lazy way that often works.