Trying to time the market — waiting for the "right moment" to invest — feels intuitive, but it consistently underperforms a much simpler strategy: investing a fixed amount on a regular schedule, regardless of what the market is doing, and letting time do the heavy lifting.
An investment projection combines two growing pieces: any initial lump sum you start with, and every future monthly contribution, each compounding for however much time remains until your target date. Because contributions made early in your timeline have decades to compound while contributions made later have only a few years, the total projection is disproportionately shaped by how early — not how much — you started.
How the Growth Is Calculated
Each month, your existing balance earns that period's return, and then your new contribution is added on top, becoming part of the balance that earns returns in every subsequent month. Run that process forward across your full timeline, and the ending balance separates cleanly into two figures: your total contributions (the money you actually put in) and your total growth (everything the market added on top).
A Worked Example
Investing $5,000 to start, then $250/month, at an assumed 8% average annual return: after 15 years, the balance reaches roughly $92,000, of which $50,000 is your own contributions and about $42,000 is investment growth — growth is already close to half the total. Extend the same monthly contribution to 30 years instead, and the balance grows to around $412,000, with contributions of just $95,000 and growth of roughly $317,000 — growth now makes up more than three-quarters of the total, illustrating how dramatically the growth share increases with time.
Common Mistakes to Avoid
- Trying to time entries and exits: consistent contributions ("dollar-cost averaging") smooth out volatility and remove the need to guess market direction, which even professional investors struggle to do consistently.
- Stopping contributions during downturns: market drops are exactly when your fixed contribution buys more shares at a lower price — pausing during a downturn undermines the strategy.
- Using an overly optimistic return assumption: 10-12% reflects raw historical stock market averages before inflation; 6-8% is a more conservative, planning-appropriate range.
- Underestimating fees: a 1% annual management fee compounds negatively over decades the same way returns compound positively — it's a meaningfully larger cost than it first appears.
Bottom Line
Consistency compounds. Use an Investment Calculator to project your own lump sum and monthly contributions across different timelines, and see how much of your future balance comes from what you put in versus what the market adds on top.