Compound Quest · An investing simulator for kids
Warren Buffett bought his first stock at 11. See what your start could become.
Pick real investments, like the S&P 500, NVIDIA or Bitcoin. Set what you'd put in each month. Then watch what time does to it, and what that money could pay for when you're older. Built by a dad for his two boys, free for every kid.
01 · The simulator
Build your plan. Watch it grow.
Everything updates live. Hit play to watch your money grow year by year.
Pick up to 6. Past returns on each card are real, but they don't predict the future.
02 · What it could mean for you
Money that pays you, even when you're not working.
A common rule: you can take out about 4% a year and your money keeps growing behind it. That's a paycheck you never have to clock in for. Everything here is in today's dollars, using the "most likely" outcome.
| Age | Most likely | Range | Could pay you |
|---|
03 · The cost of waiting
Same plan. Different start. Huge difference.
Your exact plan, started now vs. a few years from now. Value at 65, in today's dollars.
"Someone's sitting in the shade today because someone planted a tree a long time ago."
Warren Buffett04 · Inflation
Why money sitting still slowly shrinks.
Inflation means prices go up over time. The stuff doesn't get better. Your dollar just buys less of it. Here's what some things cost in 1990, when your parents were kids, vs. 2025.
What it could buy, measured in today's prices. Assumes 3% inflation, a savings account earning about 3%, and investments growing about 8% a year.
05 · Crypto
Crypto: money built on the internet.
Crypto isn't fake money. It runs on blockchains: a shared record book that thousands of computers around the world keep a copy of. Nobody can secretly change it, it never closes, and it doesn't need a bank in the middle.
You send it
You send 0.001 Bitcoin to a friend. That message gets shared with computers all over the world.
Thousands check it
Those computers check that you actually have it and aren't spending it twice. No bank, no boss. Just math everyone agrees on.
It's locked in forever
It goes into a "block" that's chained to every block before it. Changing it would mean redoing the whole chain faster than everyone else. Basically impossible.
The first crypto. Only 21 million will ever exist, and nobody can print more. Dollars can be inflated away; Bitcoin's supply can't. That's why people call it digital gold.
A blockchain that runs apps. "Smart contracts" are programs that move money automatically when rules are met, with no company in charge. Thousands of apps, games and digital dollars run on it.
A blockchain designed to be super fast and cheap: thousands of transactions a second for a fraction of a penny each. Popular for payments, games and trading apps.
Built to move money between countries in seconds instead of days. Payment companies and some banks use its network to send money around the world.
Someone paid 10,000 Bitcoin for two pizzas. Today those coins would be worth hundreds of millions of dollars. 🍕
The U.S. approved Bitcoin and Ether ETFs, so regular investing accounts can hold them. BlackRock's Bitcoin fund became one of the fastest-growing ETFs in history.
The U.S. government created a Strategic Bitcoin Reserve and passed its first law for stablecoins, digital dollars that live on blockchains.
Banks, payment companies and big tech firms are building on blockchains for payments, savings and apps.
06 · Rewind: what really happened
What if you'd started back then?
Real prices, adjusted for splits and dividends. Your exact plan, run through actual market history. No guesses.
Loading real market history…
07 · What the research says
Why most pros start with index funds.
Try putting 100% in one company above and compare it to the S&P 500. The most likely outcome is often lower, and the range is way wider. Here's the research behind that.
of stocks did all the work
Of U.S. stocks from 1926 to 2016, about 4% created all of the market's net wealth. More than half did worse than safe government bonds. Own the whole market and you own the winners automatically.
Bessembinder, Journal of Financial Economics (2018)
pros lose to the index
Over 15 years, roughly 9 out of 10 professional U.S. large-company fund managers did worse than the plain S&P 500. A cheap index fund beats most experts.
S&P Dow Jones Indices, SPIVA U.S. Scorecard
Missing 10 days halves it
Missing just the 10 best days over 20 years cut returns roughly in half, and most best days came within two weeks of the worst. Stay invested through the scary parts.
J.P. Morgan Asset Management, Guide to Retirement
losing 20-year periods
Since 1926, the S&P 500 (with dividends reinvested) has never lost money over any 20-year stretch. Over one year it loses about 1 in 4 times. You have 50+ years.
Historical S&P 500 total returns
We don't assume a stock keeps doing what it did lately. NVIDIA's last 10 years, repeated for 50, would turn $100 a month into more money than exists on Earth. Instead, each investment gets an expected return based on how much it moves with the market (the CAPM model Wall Street analysts use), plus its own level of risk. Riskier picks can earn more on average, but their range is much wider and their most likely outcome is often lower. That's why diversifying matters. The chart runs 3,000 possible futures and shows the middle one and the range.
08 · For parents
Turning the simulator into a real account
How kids can actually invest
- Custodial brokerage account (UTMA/UGMA): a parent opens and manages it, and the money belongs to the child, transferring at 18 or 21 depending on your state. Most large brokerages offer one with no minimum.
- Custodial Roth IRA: growth is tax-free for life. Requires earned income (mowing, babysitting, pet-sitting, real work), and contributions can't exceed what they earned that year. Keep a simple log of jobs and pay.
- What to buy: most families start with a low-cost, broad index fund (total U.S. market, S&P 500, or total world) with a yearly fee of 0.10% or less, plus automatic monthly investing.
- Crypto for kids: kids can't open their own crypto exchange accounts. The simplest route is a Bitcoin or Ether ETF bought inside a custodial brokerage account, which avoids handling private keys. Keep it a small slice and talk through the swings before they happen.
- Make it real: offer a match (like a 401(k)), check the account together monthly, and point out every dividend: "the company just paid you for owning it."
Methodology & data
- Projections: 3,000 simulated futures with yearly lognormal returns. The S&P 500's median growth is set by the scenario (6%, 8%, or 10%). Each holding's expected return follows CAPM with a 4% risk-free rate and an approximate beta; volatility is an approximate long-run figure. Each holding is simulated separately (buy-and-hold) and linked through shared stock-market and crypto shocks, so diversification is reflected. ETF fees are subtracted.
- Crypto: CAPM doesn't fit crypto well, so Bitcoin's typical (median) yearly growth comes from the Crypto outlook setting: it starts at 20% (Middle) or 35% (Bullish) and eases toward the stock scenario's growth with a 15-year time constant, reflecting an asset still early in adoption; Cautious matches stocks throughout. Middle implies roughly 9× today's Bitcoin price in 15 years, Bullish roughly 28×. Other coins get Bitcoin's average (arithmetic) return with their own higher volatility, so extra risk isn't rewarded. Starting volatility is high (Bitcoin ~55%, Ether ~70%, Solana ~90%, XRP ~80%, in log terms) and fades toward lower levels over roughly a decade, as Bitcoin's has historically. Crypto is modeled as about 0.35 correlated with stocks and about 0.75 with other coins.
- "Most likely" is the median outcome; the range is the 10th to 90th percentile. "Today's dollars" deflates by 3% inflation a year.
- Rewind uses real month-end prices adjusted for splits and dividends (Yahoo Finance; crypto priced in U.S. dollars), refreshed every 12 hours. Contributions are added monthly and split by your percentages, without rebalancing. If a holding wasn't public yet, the rewind starts when it was.
- "Could pay you" uses the 4% withdrawal guideline. Prices for cars, college, rent, and homes are rough U.S. averages.
- Educational only. Not financial advice or a recommendation to buy any security. Past performance does not predict future results.
Privacy
No accounts, no ads, and no tracking on this page. Your plan is saved only in this browser. The share link puts the plan in the URL so you can send it to a parent.