How the numbers work

The guides on this site show their arithmetic rather than asserting a result. There are 1,863 worked calculations across 345 guides, made up of 7,867 individual lines, and this gathers them by subject.

A calculator gives you an answer. These show how one is reached, which is what you need when you have to check it, explain it to an employer, a lender or Inland Revenue, or follow the same steps with your own figures.

What one looks like: The channel switch

  1. End the call. Not on hold, not transferred. Hang up.
  2. Ring back on a number you already had, from your own contacts or the back of your card.
  3. If you cannot reach them, contact someone else who can, another family member or the office.
  4. Do nothing financial until you have, regardless of what the urgency was said to be.

No genuine emergency is made worse by a five minute callback. Every scam is destroyed by one.

Guides and learning 568 worked calculations

Questions answered in the written guides, from budgeting and KiwiSaver to household spending and employment agreements.

Running a business 261 worked calculations

Margins and break even, cash flow and runway, pricing, subscription revenue, customer value and the true cost of an employee.

Mortgages and lending 151 worked calculations

Repayments and interest, fixed against floating, refinancing and break fees, offset and revolving credit, and what a bank will lend.

Tax on investments and property 95 worked calculations

The bright line test, foreign investment fund rules, tax on interest and dividends, PIE rates and rental income.

Income tax and PAYE 89 worked calculations

Tax codes and secondary tax, PAYE deductions, brackets and marginal rates, refunds, and what actually lands in your account.

Benefits, ACC and student support 88 worked calculations

ACC levies and weekly compensation, Working for Families, the Accommodation Supplement, superannuation, student loans and allowances.

Renting, flatting and landlords 81 worked calculations

Rent affordability and flatmates, bonds, rental yield, healthy homes, boarders and the sums a landlord runs.

Saving and investing 79 worked calculations

Compound interest, managed funds and fee drag, term deposits, shares and dividends, and what a return really nets you.

KiwiSaver 74 worked calculations

Contributions and the government contribution, employer rates and ESCT, funds and fees, first home withdrawals and what happens on death.

Budgeting and prices 66 worked calculations

Household budgets, splitting costs, comparing prices and working out what something really costs you.

GST and business tax 63 worked calculations

GST on a price or a total, provisional tax, company tax, fringe benefit tax, entertainment, mileage and what a contractor owes.

Loans and debt 57 worked calculations

Personal loans and car finance, credit cards, hire purchase and buy now pay later, and the order to clear debts in.

Retirement planning 51 worked calculations

How long savings last, what an income in retirement takes, drawdown rates and the gap between a plan and a number.

Buying a home 48 worked calculations

Deposits and first homes, what a place really costs to own, rates and insurance, building, and buying against renting.

Leave and pay entitlements 35 worked calculations

Annual leave, sick leave and public holidays, parental leave, redundancy and notice, trial periods and how each is paid.

Currency and inflation 23 worked calculations

Exchange rates and the spread a bank takes, what inflation does to a sum over time, and comparing prices across years.

Selling a home 17 worked calculations

Agent commission and what it covers, auctions and marketing, appraisals, settlement, and what is left after a sale.

Vehicles and travel 17 worked calculations

What a car costs to run, road user charges, fuel against electricity, trips and distances, and comparing a commute.

Every working is taken from the guide that shows it, and that guide is where any rate or threshold is kept current. These are worked examples for education, not advice. Last reviewed 2026-09-06. See also every question the site answers, the A to Z of every page and the guides.