Is it better to invest a lump sum all at once or spread it out monthly?

If you have a lump sum and the question is purely about expected returns, investing it all at once has come out ahead roughly two-thirds of the time in historical studies. The reason is simple: the market rises more often than it falls, so money sitting in cash waiting to be invested usually misses gains rather than avoiding losses.

The case for spreading it out, dollar-cost averaging, is about regret. If you invest $50,000 on a Monday and the market drops 12 percent by Friday, it is hard to stay the course. Spreading the same amount over six or twelve months means you are never all-in at a peak, and the worst case is much gentler. That psychological safety has real value if it stops you from panicking.

A common compromise is to invest half now and the rest over the following several months. It captures most of the expected benefit of going in immediately while cushioning the worst outcomes.

What matters more than either method is that the money actually goes in. The lump sum sitting in a savings account "until things settle down" is the outcome that costs the most, and it is the most common one.