Choose the tool that matches the decision

Start with the question you need to answer. Each working page below either calculates a result, builds an editable worksheet, or explains an assumption used by a tool.

Seven interactive calculatorsOne manual emergency-fund worksheetMethods you can reproduce

Question-to-tool decision map
Your question	Open this	Result you receive
What would this home cost each month?	All-in mortgage calculator	Loan payment, entered ownership costs, scenarios, extra-payment effect, and CSV amortization.
Does that payment fit my own cash flow?	Affordability worksheet	A housing ceiling after the debts, essentials, savings, and buffer you choose.
How much cash does the purchase require?	Cash-to-close worksheet	Itemized purchase and move cash, credits, and the remaining reserve.
What changes if I rent instead?	Rent-versus-buy model	Multi-year net costs and three home-value scenarios.
What is actually financed in this car deal?	Itemized auto-loan calculator	Price, tax, fees, trade equity, rebate, payoff schedule, term comparison, and CSV.
What deposit reaches my savings target?	Savings goal calculator	Future balance, required monthly deposit, target time, and yearly milestones.
How sensitive is a long-term projection?	Investment scenario calculator	Return range, fees, inflation-adjusted value, contribution growth, and yearly schedule.
How was a result tested?	Calculation methodology	Formula conventions, public test vectors, rounding rules, and change record.

Flagship topic cluster

Complete a home decision without switching assumptions

Move the same price, down payment, rate, and ownership period through four different questions. Each page measures something the others do not.

Build the monthly cost

Add local tax, insurance, HOA, PMI, and an optional extra payment to the fixed-rate loan.

Test household cash flow

Protect essential spending, debt payments, planned savings, and a user-chosen buffer before housing.

Reconcile purchase cash

Separate down payment, closing estimate, prepaids, move-in costs, and written credits.

Change the time horizon

Compare modeled rent with ownership cash out and estimated sale proceeds over the planned stay.

The calculator playbook, consolidated

Use any estimate in four passes

Evidence pass: replace defaults with figures from a statement, quote, written offer, local authority, or account disclosure.
Base pass: record the result and the assumptions that produced it. A number without its inputs cannot be checked later.
Stress pass: change one uncertain assumption at a time. The built-in scenario tables do this for rates, terms, returns, and appreciation.
Decision pass: compare the output with cash flow, liquidity, timing, and costs the model explicitly leaves out.

A calculator narrows a question; it does not turn an assumption into a fact. Download or print the result when a page provides that option, then replace it with the lender, dealer, bank, insurer, tax authority, or investment-provider document before acting.