Tools
13 working calculators and simulators
Every tool reads from one shared profile, so changing your income in one place updates all of them. Each shows the reasoning behind its output and links to the research it rests on.
Foundations
The steps that come before investing, in the order the arithmetic puts them.
Emergency fund sizer
calculatorHow much cash should I actually hold?
Sizes a buffer from your income stability and dependents rather than a generic three-to-six month rule, and shows what each factor added.
2 min2 evidence notesuses your profileDebt payoff planner
calculatorHow long until I am debt free, and what does the order cost me?
Simulates avalanche and snowball month by month, and prices the interest difference so you can decide what motivation is worth.
4 min1 evidence noteuses your profileDebt vs invest
calculatorShould this money clear a debt or buy an index fund?
Compares a guaranteed return against an expected one on a risk-adjusted basis, accounting for tax on both sides.
3 min2 evidence notesuses your profile
Building wealth
Contributions, costs and what to own.
Contribution projector
calculatorWhat does saving this much a month actually become?
Projects a contribution plan in both nominal and inflation-adjusted terms, because the second number is the one that buys things.
3 min2 evidence notesuses your profileFee drag calculator
calculatorWhat is a 1% fee really costing me?
Compares identical plans across fee levels and expresses the gap in years of contributions — the number that tends to land.
2 min3 evidence notesuses your profileAllocation and risk capacity
calculatorHow much risk can I take, and how much can I stand?
Separates risk capacity from risk tolerance, takes the lower of the two, and shows the drawdown the result implies.
4 min3 evidence notesuses your profile
Retirement and drawdown
Targets, ranges, and the risk of a bad decade.
401(k) optimizer
calculatorAm I leaving employer money on the table?
Runs your plan year pay period by pay period against the current IRS limits, prices the match you are declining, and settles traditional versus Roth in one comparison of two tax rates.
4 min3 evidence notesuses your profileRetirement number
calculatorHow much do I need, and am I on track?
Builds a target from your desired spending and a withdrawal rate you choose, with the assumptions behind each rate spelled out.
5 min3 evidence notesuses your profileMonte Carlo projection
simulatorWhat is the range of outcomes, not just the average?
Runs thousands of correlated stock and bond paths and reports the distribution in real terms, including how often the plan fails.
5 min3 evidence notesuses your profileSequence risk explorer
simulatorWhat if I retire into a bad decade?
Runs your withdrawal plan from every historical starting year since 1928, so you see the spread rather than one average.
5 min2 evidence notesuses your profile
Decisions under uncertainty
The gap between what portfolios return and what investors earn.
Lump sum vs averaging in
simulatorI have a windfall. All at once, or spread out?
Tests both strategies against every historical start year and prices what averaging in costs — and what it buys.
3 min2 evidence notesThe cost of being out
simulatorWhat does missing the best years cost?
Shows the concentration of returns — and, unusually, the symmetric case of dodging the worst years, so you can judge the argument honestly.
3 min2 evidence notesThe decision simulator
simulatorHow would I actually behave in a crash?
Twenty years of real market history with the dates hidden. You allocate each year, then find out what your decisions cost against simply holding.
10 min3 evidence notes
Every tool cites its sources
The claims these tools make are not house opinion. They trace to specific findings in the evidence library, each with its citations, its effect size, and the conditions under which it stops being true.
- A cash buffer is what makes every other decision survivable
- The order of returns decides retirements that averages cannot explain
- Clearing debt is a guaranteed return; investing is not
- Unclaimed employer matches are the clearest mistake in personal finance
- Defaults beat intentions, so remove the decision
- Fees are the most reliable predictor of returns you control
- Most active funds underperform, and past winners rarely repeat
- Tax drag is a fee you can often remove entirely
- Most individual stocks lose money; a few pay for everything
- Losses hurt about twice as much as equivalent gains feel good
- Building a plan on US returns is a bet, not a neutral assumption
- The 4% rule is a historical result with three heavy assumptions
- Investing a windfall at once usually wins, but averaging in buys something real
- Market timing requires being right twice, and the good days cluster in the bad times
- Investors underperform the funds they own