car-tcoCompare the total cost of car ownership across buy-new, buy-used, lease, and keep-your-current-car — depreciation, insurance, maintenance ramp, and fuel over a real horizon, not just the monthly payment. Use when asked should I lease or buy a car, is it cheaper to keep my old car, what does this car
cohort-curve-modelFit a retention curve to observed cohort data and project LTV — computed, not estimated. Use when someone has real cohort retention numbers (month 0, 1, 2…) and asks what lifetime value, lifetime periods, or long-run retention they imply, or whether retention is flattening or leaking. Produces a fit
college-costCompute what a degree will actually cost — sticker minus real aid, inflated per year, split into cash and loans, with the loan's decade-long monthly tail made visible before enrollment instead of after. Use when asked what will college really cost, compare these two offers' real prices, how much loa
daycare-vs-stay-homeRun the real math on a parent leaving work versus paying for childcare — the second income net of daycare, marginal taxes, and work costs, AND the career-trajectory cost of years out, over horizons instead of one brutal year. Use when asked does it make sense for me to keep working, daycare costs my
debt-payoffBuild a debt payoff plan — avalanche vs snowball simulated month by month on your actual debts, the real payoff dates, and the psychology-vs-arithmetic tradeoff priced in dollars. Use when asked how do I pay off my debts, avalanche or snowball, make me a debt payoff plan, or when will I be debt-free
decision-tree-solverTurn a fork-in-the-road decision into a computed expected-value tree — settle or sue, launch or wait, fix or replace — rolled back by the bundled script, with the break-even probability where the answer flips. Use when asked should we settle or go to trial, build a decision tree, what probability ma
emergency-fundSize an emergency fund from essential spend and real risk factors — not a one-size 'six months' — with the funding timeline and where the money should sit. Use when asked how big should my emergency fund be, do I have enough saved, emergency fund or invest, or how many months of expenses do I need.
ev-vs-gasCompare an EV against a comparable gas car on total cost — upfront gap after incentives, energy vs fuel per year, maintenance delta, and the crossover year when the EV pulls ahead (or doesn't). Use when asked is an EV worth it, EV vs gas total cost, when does an EV pay for itself, or should my next
exit-waterfallCompute who gets what at each exit price from a cap table — liquidation preferences, conversion points, and where the founders' share collapses. Use when asked to model an exit waterfall, what do I get if we sell for X, explain liquidation preferences on my cap table, or compare payouts across exit
fair-splitDivide things that cannot be divided — an inherited house, a dissolved partnership, the furniture after a breakup — using sealed-bid fair division (Knaster), computed by the bundled script so everyone ends provably above their own fair share. Use when asked to split an estate fairly, divide assets b
fire-numberCompute a financial-independence (FIRE) target and years-to-reach with every assumption labeled as an assumption — plus a sensitivity table instead of a single false-precision answer. Use when asked what's my FIRE number, when can I retire early, how much do I need to be financially independent, or
freelance-rateDerive a freelance day/hourly rate backwards from target income, honest billable utilization, overhead, and the self-employment tax premium — the arithmetic that proves a rate is not salary÷2000. Use when asked what should I charge as a freelancer, how do I set my consulting rate, why is my freelanc
offer-comparisonCompare two or more job offers as total-comp curves over four years — vesting cliffs, bonuses, 401(k) match, and the crossover year computed, not vibed. Use when asked to compare job offers, which offer pays more over time, model my equity vesting, or is the startup offer actually worth it. Produces
pricing-calculatorModel pricing scenarios — tiers, margins, break-even, and the revenue impact of a price change. Use when asked to calculate pricing, model a price increase, find break-even volume, set tier prices to a margin target, or estimate the revenue effect of a pricing change. Produces a computed pricing mod
pricing-sensitivity-modelVan Westendorp price sensitivity, computed from real survey answers — crossings found by interpolation, not read off a chart by eye. Use when someone has (or plans) the four-question pricing survey (too cheap / cheap / expensive / too expensive) and needs the optimal price point, the acceptable rang
raise-vs-jumpModel staying for annual raises vs job-hopping for bigger bumps — cumulative earnings trajectories, the crossover year, and the costs the salary math hides (vesting resets, promotion paths, search risk). Use when asked should I switch jobs for more money, is job hopping worth it, model my salary if
refinance-breakevenCompute the month a refinance actually starts saving money — payment delta, breakeven month, and total interest on both paths including the term-reset trap. Use when asked should I refinance, when does a refi break even, compare my loan to a refi offer, or is this refinance worth the closing costs.
rent-vs-buyModel rent-vs-buy honestly — year-by-year net position for both paths including the assumption everyone drops (the renter invests the difference), with a breakeven horizon instead of a verdict. Use when asked should I rent or buy, does buying beat renting in my city, when does buying break even, or
roi-estimatorEstimate the ROI, payback, and NPV of an investment, project, or purchase. Use when asked to calculate ROI, build a business case, justify a purchase/initiative, work out payback period, or compare options by return. Produces a computed ROI summary (net benefit, ROI %, payback, simple NPV) with the
runway-calculatorCalculate cash runway, burn, and the zero-cash date — and whether you're default alive or dead. Use when asked to work out runway, monthly burn, when the money runs out, or how much to raise/cut to reach a target. Produces a computed runway summary (net burn, months of runway, zero-cash date, defaul
runway-monte-carloCash runway as a distribution, not a number — Monte Carlo simulated. Use when someone asks how long their cash lasts, when to start fundraising, or how burn/revenue volatility changes their runway; especially when the naive cash÷burn answer is driving a decision. Produces P10/P50/P90 runway, month-b
saas-metricsCompute the core SaaS metrics — MRR/ARR, growth, NRR/GRR, churn, quick ratio, magic number — from your numbers. Use when asked to calculate SaaS metrics, MRR/ARR, net revenue retention, the quick ratio, or to build a SaaS metrics snapshot for a board/investor update. Produces a computed metrics dash
schedule-monte-carloProject completion as a distribution, not a date — Monte Carlo over the task graph. Use when a plan's finish date came from summing 'likely' estimates (it's wrong, mathematically), when leadership needs a commit date, or when you need to know which tasks actually control the timeline. Produces P10/P
solar-breakevenModel whether solar panels pay for themselves for your roof — net cost after incentives, bill offset with degradation, electricity inflation, the inverter replacement, and the breakeven year, plus the policy risk no calculator controls. Use when asked are solar panels worth it, when does solar break
student-loan-strategyDecide what the extra money does about student loans — attack them, invest alongside them, or ride a forgiveness track — with the three paths simulated on your actual loans and the guaranteed-vs-assumed framing kept honest. Use when asked should I pay off my student loans faster, pay loans or invest
subscription-auditFind and rank the recurring-payment leak — every subscription annualized, sorted by real yearly cost, with the keep/cancel/downgrade pass and the where-they-hide checklist. Use when asked audit my subscriptions, how much am I spending on subscriptions, help me cancel stuff, or what recurring charges
support-staffing-modelHow many support agents does the queue actually need — Erlang C, computed, not 'tickets per agent' folklore. Use when staffing a support/CS team, defending headcount, or checking whether an SLA is mathematically possible with the current roster. Produces agent counts across load scenarios (with shri
tornado-sensitivityWhich assumption actually moves the answer — one-at-a-time sensitivity, ranked into a tornado. Use when a model's output is being argued about (LTV, ROI, forecast) and the room is debating drivers that don't matter, or before spending diligence effort: swing every driver low→high and see which one o
unit-economicsModel the unit economics of a business — CAC, LTV, payback, contribution margin — from real inputs. Use when asked to calculate unit economics, work out LTV:CAC, find the payback period, or check whether a business model is viable per customer. Produces a computed unit-economics summary (LTV, CAC, r
wedding-budgetBuild a wedding budget that survives to the wedding — allocation by real shares, the per-guest lever made explicit, the routinely-forgotten line items priced in from day one, and a contingency that isn't decorative. Use when asked make a wedding budget, how do people split X across a wedding, we hav