Investing & Compound Growth
See what consistent contributions actually turn into over decades.
Investing outcomes are driven by three things you control — how much you contribute, how long you stay invested, and how much you pay in fees — and one you don't, which is the return the market delivers.
These tools separate those levers so you can see which one matters for your situation. For most people under 40, contribution rate dominates. For most people over 55, sequence of returns and withdrawal rate dominate.
Tools
Investing calculators
AI Investment Advisor
Educational allocation frameworks based on your horizon and risk tolerance — plus what fees would cost you.
Compound Interest Calculator
See the balance, the split between contributions and growth, and what it actually buys.
Investment Return Calculator
Your headline return is not your return. See what survives fees, taxes and inflation.
Inflation Calculator
Translate future dollars into today's purchasing power — the adjustment most plans skip.
Most used here
Guides
Understand the decisions behind the investing numbers.
- beginner11 min read
Investing for Beginners
A beginner's guide to investing in the US: account order, index funds, fees, asset allocation and the behavioral mistakes that cost the most.
Updated January 15, 2026
- beginner6 min read
Understanding Inflation
How inflation erodes purchasing power, what protects against it, and why every long-range financial projection needs an inflation adjustment.
Updated January 15, 2026
Related goals
See how investing fits into the bigger picture.
Invest Better
Contribution rate, time and fees — in that order.
Plan Retirement
Find the number, then find the date it becomes reachable.
Save More Money
Build the cushion, automate the habit, and raise the yield.
Not sure where to start?
Describe your investing situation and the AI coach will point you to the right tool and walk through the trade-offs.
Investing questions
What return should I assume when planning?
The US stock market has returned roughly 10% annually before inflation over the long run, or about 7% after it. Planning with the inflation-adjusted figure is safer because it expresses future balances in today's purchasing power. Many planners use 6–7% real for equity-heavy portfolios and lower for balanced ones. Assume less rather than more — an over-optimistic assumption produces a plan that quietly under-saves for decades.
How much difference do investment fees really make?
Far more than most people expect, because fees compound against you. On a $500,000 portfolio over 30 years at 7%, moving from a 1% expense ratio to 0.05% leaves roughly a third more money at the end. Fees are also the only variable in the entire equation you can change with certainty.
Should I invest a lump sum or spread it out?
Historically, investing a lump sum immediately beats spreading it out about two-thirds of the time, simply because markets rise more often than they fall. Spreading it out is a behavioral hedge, not a mathematical one — it reduces regret if the market drops right after you invest. If the anxiety of a lump sum would cause you to abandon the plan, spreading it out is the better choice despite the lower expected value.
What is the difference between nominal and real returns?
Nominal return is the raw percentage gain. Real return subtracts inflation and reflects what your money can actually buy. A 7% nominal return during 3% inflation is a 4% real return. Long-range projections shown in nominal dollars look impressive and mislead — a $2 million balance in 30 years buys roughly what $825,000 buys today at 3% inflation.