Investment return with contributions

Why total gain is not the return

Turning $180,000 into $610,000 is a 239% total gain. But nobody earned 239% on anything. The money you contributed in year 29 was invested for one year, not thirty.

Each contribution has its own holding period, so a portfolio built from regular payments has a weighted average holding period far shorter than the plan's length. That is why comparing "total gain" against an annual return figure is meaningless once contributions are involved — they are not measuring the same thing.

Timing within the plan

Contributing at the start of each period rather than the end gives every payment one extra period of growth. Over 30 years that is worth roughly 7% more at the same rate — a meaningful gain from a scheduling choice.

Front-loading matters more. Contributing heavily in the first ten years and then stopping usually beats starting ten years later and contributing for twenty, because the early money compounds for the whole horizon.

Three things that quietly reduce it

Fees compound in reverse. A 1% annual fee does not cost 1% — it removes a slice of the balance every year, and that slice would have compounded. On this example it is worth well over $100,000 across thirty years.

Tax reduces realized gains depending on the account. The same contributions in a tax-advantaged account versus a taxable one can diverge substantially, which is usually a larger decision than the choice of investment.

Inflation does not change the balance, but it changes what the balance buys. $610,000 in thirty years is not $610,000 of today's spending power.

It is a scenario, not a forecast

These projections assume a steady return. Real markets do not deliver 7% annually; they deliver something far more erratic that may average near it. The order of returns matters too — a poor decade at the end hurts far more than the same decade at the start, because it lands on a much larger balance.

Test several rates rather than trusting one. If the plan only works at 9%, it is not a plan.

Model your own

The investment return calculator handles contributions, timing, fees, tax and inflation with year-by-year balances. For a simpler growth view use the compound interest calculator, and for a target-based plan the retirement calculator.

Related reading: compound interest explained and inflation and real returns.

How contributions and returns trade off

A projection with regular contributions has two engines. Early on the contributions dominate; later the returns do. Knowing which phase you are in tells you which lever to pull.

Growth overtakes contributions somewhere around year eighteen at this rate. Before that point, raising the contribution matters more than the return. After it, time in the market does the work.

Common questions

Related reading

The rest of this series, and the calculators that let you run the idea on your own numbers.

More investing and retirement guides

• Compound interest explained — $10,000 at 7% becomes $76,000 over 30 years. Simple interest would give $31,000. The $45,000 difference is compounding, and it is almost all in the final decade.
• Retirement savings target — Wanting $60,000 a year implies $1.5m at a 4% withdrawal rate — but $3.1m if you retire in 25 years and inflation runs at 3%.
• Inflation and real returns — $100,000 at 7% for 30 years becomes $761,000, or about $313,000 in purchasing power. Both numbers are correct, and only one is useful.

Try it with your figures

• Compound Interest Calculator
• Investment Return Calculator
• Retirement Calculator

See also all guides, every calculator, and the calculation methodology behind these estimates.