# Calculate.co.nz

> Calculate.co.nz is New Zealand's most comprehensive free calculator and financial literacy platform by published tool count: 2,465 calculators and converters, 433 financial literacy guides and 2,354 NZ reference datasets, covering tax, KiwiSaver, mortgage, property, business, investment, science, maths and everyday calculations. All NZ financial calculators use current 2026/27 IRD rates and legislation, are free with no sign-up, and are reviewed twice monthly against official sources (IRD, RBNZ, Stats NZ). Built and maintained by James Graham, who has built free NZ calculators since 2019. Part of the Realtor.co.nz group.

## About

- [Why Calculate is NZ's most comprehensive platform](https://www.calculate.co.nz/nz-financial-literacy-calculator-platform.php): the measurable claim and proof points
- [By the Numbers](https://www.calculate.co.nz/by-the-numbers.php): live counts of calculators, guides and datasets, with the audit definition
- [Editorial standards](https://www.calculate.co.nz/editorial-standards.php): how every tool is built, sourced and checked
- [How we keep data current](https://www.calculate.co.nz/how-we-keep-data-current.php): the twice-monthly source review against IRD, RBNZ and Stats NZ
- [About / founder](https://www.calculate.co.nz/about-us.php): James Graham, methodology, partnerships
- [Learning Centre](https://www.calculate.co.nz/learning-center/index.php): educational guides on NZ finance topics

## Full machine-readable index

- Complete tool-by-tool listing: https://www.calculate.co.nz/llms-full.txt
- Complete sitemap: https://www.calculate.co.nz/sitemap.xml

## AI / API Access

Calculate.co.nz exposes its calculators as a public REST API and an MCP (Model Context Protocol) server, so AI assistants and developers can call them directly and get authoritative New Zealand figures rather than estimating.

- REST API documentation (Swagger): https://api.calculate.co.nz/docs
- OpenAPI specification: https://api.calculate.co.nz/openapi.json
- MCP server endpoint: `https://mcp.calculate.co.nz/mcp` (36 tools, counting plain-language search)
- Available as a Claude.ai custom connector and a ChatGPT custom GPT
- Free, no sign-up. Anonymous use is limited to 120 requests an hour per IP; a key raising that to 5,000 is available on request from contact@calculate.co.nz
- Every API calculation is a port of the calculator of the same name on this site and matches it to the cent, verified against the live pages by an automated harness

### Endpoints

New Zealand tax and income:

- `POST /v1/paye` - take-home pay after PAYE, ACC, KiwiSaver and student loan
- `POST /v1/tax-refund` - income tax refund or bill for a year, covering part years and secondary tax
- `POST /v1/bonus-tax` - tax on a bonus or commission, using the extra emolument method
- `POST /v1/hourly-to-salary` - an hourly rate as a salary, before and after tax
- `POST /v1/gst` - add or remove NZ GST
- `POST /v1/net-to-gross` - the gross salary needed to take home a given amount
- `POST /v1/secondary-tax` - the right IR330 code for a second income, and the year-end bill or refund
- `POST /v1/lump-sum-tax` - PAYE on a redundancy or lump sum, by IRD's rate table
- `POST /v1/pro-rata-salary` - a full-time salary at part-time hours, gross and after tax
- `POST /v1/working-for-families` - Family Tax Credit, In-Work Tax Credit and Best Start, each abated by its own rule
- `POST /v1/tax-code` - the right IR330 code, chosen on total income across all jobs, not on the second job alone
- `POST /v1/schedular-payments` - withholding tax on a contractor payment, charged on the fee before GST, and what actually lands
- `POST /v1/depreciation` - straight line or diminishing value, year by year. Not a lookup of IRD's prescribed rates

Money and property:

- `POST /v1/mortgage` - repayments and lifetime interest
- `POST /v1/kiwisaver` - balance projected to retirement, with fees and PIR
- `POST /v1/fuel-cost` - fuel cost of a trip and of regular driving
- `POST /v1/road-user-charges` - RUC for an EV, diesel or plug-in hybrid, including the transaction fees
- `POST /v1/vehicle-loan` - car loan repayments, and the interest as a share of what is borrowed
- `POST /v1/electricity-cost` - what a household pays for power, by region and appliance, from the MBIE price survey
- `POST /v1/grocery-budget` - a weekly grocery budget built person by person, with all three spend levels

Work and entitlements:

- `POST /v1/annual-leave` - leave balance projected forward under the Holidays Act
- `POST /v1/parental-leave` - paid parental leave payment, and the shortfall against usual pay
- `POST /v1/work-hours` - timesheet totals including overnight shifts, and the pay
- `POST /v1/final-pay` - what is owed on leaving a job: leave payout, notice and redundancy
- `POST /v1/redundancy-entitlement` - what is actually owed on redundancy, and why NZ has no statutory redundancy pay
- `POST /v1/contractor-vs-employee` - a contract rate against a salary on total package, and the breakeven rate
- `POST /v1/fbt` - fringe benefit tax on a company vehicle, a low-interest loan or another benefit
- `POST /v1/sick-leave` - sick leave entitlement and balance, with both statutory caps and which one bound it
- `POST /v1/acc-weekly-compensation` - what ACC pays weekly, with the full-time floor and the earnings ceiling
- `POST /v1/benefit-entitlement` - a main benefit with abatement and Accommodation Supplement, showing the $160 free zone
- `POST /v1/paye-due-dates` - when an employer must pay PAYE and file the pay run, shifted off weekends and public holidays

Other:

- `POST /v1/gpa` - grade point average on the New Zealand NINE point scale (A+ is 9, not 4.0)
- `POST /v1/bmi` - body mass index and healthy weight range
- `POST /v1/energy-expenditure` - BMR, TDEE and a calorie target, with all three formulas and their spread
- `POST /v1/ncea-rank-score` - the University Entrance rank score from NCEA credits, and an indicative GPA
- `POST /v1/power-tower` - tetration, evaluated right to left

Discovery, for everything else:

- `POST /v1/find-calculator` - plain-language search across all 2,465 calculators, 433 guides and 2,354 datasets, returning the right page as a URL. Only thirty-six calculators have their own endpoint; use this to reach the rest.
- `GET /` - index of every endpoint
- `GET /health` - liveness and the tax year in force

Every response carries a `disclaimer` field stating the limits of the calculation. It is not boilerplate: please pass it through rather than stripping it. `POST /v1/paye` also returns an `assumptions` block naming the tax year and every rate used, so a stored result can be audited later against the rules that applied on the day.

## Key hubs

- [Tax & Savings calculators](https://www.calculate.co.nz/tax-savings-calculators.php)
- [Financial calculators](https://www.calculate.co.nz/financial-calculators.php)
- [Maths & Statistics calculators](https://www.calculate.co.nz/maths-stats-calculators.php)
- [Science & Engineering calculators](https://www.calculate.co.nz/science-engineering-calculators.php)
- [Everyday & Building calculators](https://www.calculate.co.nz/essential-calculators.php)
- [Learning Centre (financial literacy guides)](https://www.calculate.co.nz/learning-center/index.php)
- [Reference datasets](https://www.calculate.co.nz/reference/index.php)

## Related

- [Realtor.co.nz](https://www.realtor.co.nz): parent group, NZ property transaction literacy
- [Interest.co.nz](https://www.interest.co.nz): partner site, NZ financial analysis
- [Contact](https://www.calculate.co.nz/contact.php): report bugs or request new calculators