Tools
Four small calculators for the first steps of investing: emergency cash, compounding, monthly investing, and inflation. The math runs locally in your browser and turns assumptions into rough numbers, not advice.
Before you invest
The arithmetic that comes before any purchase. Pairs with the Foundations course.
Core course
The three sums this site keeps coming back to: compounding, monthly investing, and inflation. Click a preset first, then move the sliders.
- Compound interestWhat a lump sum becomes at a given yearly return over time, with the rule of 72 built in.Pairs with Foundations
- Monthly investingA fixed monthly amount, compounded monthly: final value versus what you paid in.Pairs with Investing 101
- Inflation and buying powerWhat a sum of money will still buy after years of inflation.Pairs with Foundations
Money & life
The everyday money decisions: the true cost of a car, a cash runway between jobs, splitting a household budget, the real rate on an instalment plan. Amounts are currency-neutral — read them in your own currency.
- True cost of owning a carSpread depreciation, insurance, fuel, parking and maintenance across the years you keep it.
- Student monthly allowance splitterTake out the fixed costs and your savings goal first, then see what is truly free to spend each week.
- First paycheck splitterSplit your take-home pay into essentials, forced savings and free spending, and see how long it takes to build one month of buffer.
- Household account merge simulatorCompare a 50/50 split against an income-proportional split for the shared account, and see what each partner has left.
- Family finances stress testSee the monthly gap if the higher earner loses their job, and how many months your emergency fund covers it.
- Credit card: three ways to repayCompare paying in full against instalments, and turn the flat instalment fee into a true annualized rate.
- Debt triage & payoff orderCheck whether you can cover the minimum payments; if you can, pay highest-rate debt first — if you cannot, stop the bleeding.
- Mortgage: prepay vs. keep the cashWeigh the interest a lump-sum prepayment saves against the months of liquidity it costs you.
- Family life-cover gapAdd up what your family would still owe and need, subtract what you already have, and size the life-insurance gap.
- Job-loss cash runwayDivide your available cash by unavoidable monthly costs to see how many months you can hold out, before and after cutting back.
- How much loss to keep on yourselfCompare two insurance plans by the premium gap and the worst-case exposure it buys down.
- What you can really spend on a weddingSet aside a post-wedding floor first, then see the gap against the budget — gift money excluded.
- Birth and education costs, stagedSplit a near-term birth goal from a long-term education fund, and price the education for inflation.
- Cash and tasks after losing someoneA short-term cash figure plus a 7 / 30 / 90-day checklist of the money tasks that follow.
- The long promise of supporting a parentTurn a monthly figure into a first-year total, a split between two people, and a multi-year running total.
- Where a year-end bonus should goFill needs by priority — high-interest debt, emergency fund, planned expense — and see what is left.
- What a side hustle really pays per hourStrip out costs and count every hour — delivery plus prep — to find the real net hourly rate.
- The delay cost of an impulse buyPrice a purchase per use and see how many months it pushes back a savings goal.
- Two ways to split shared moneyCompare a fifty-fifty split against an income-proportional one — what each partner keeps under both.