Margin on cost is the number NZ funders screen on, and 20% is the common hurdle. This API runs a first-pass feasibility on a New Zealand development and returns profit, margin on cost, margin of safety, residual land value, a sale-price versus build-rate sensitivity grid, a tornado ranking of which lever actually moves the deal, and goal-seek multipliers. No key, no auth, CORS open.
GET https://devstack.co.nz/api/quick-feasibility
Six 95sqm houses at $1.05m, $3,200/sqm build, $1.5m land returns GDV $6,300,000, total development cost $4,404,202, profit $1,074,059, margin on cost 24.39%, residual land value at a 20% target $1,654,247, verdict "Clears the 20% funder hurdle".
types takes up to three typologies as label:count:floorArea:salePrice, pipe separated. buildRate is $/sqm ex GST. landPrice is the purchase price. Everything else has a sensible NZ default you can override: igcPerUnit, dcPerUnit, consentsPerUnit, profFeesPct, contingencyPct, escalationPct, agentPct, interestPct, termMonths, debtPct, targetMarginPct.
Interactive version: https://devstack.co.nz/calculators/quick-feasibility
Costs broken out by line, including the two most commonly missed in NZ feasibilities: Watercare IGC and council development contributions.
Tornado sensitivity, ranked. On a typical Auckland job sale prices swing margin about twice as hard as the build rate, and the build rate about 1.5 times as hard as land price. Useful for knowing where to spend your negotiating effort.
whatHasToBeTrue gives the multiplier on sale prices or on the build rate that lands you exactly on your target margin.
Sale prices include GST and are netted at 3/23. Costs are ex GST, with no GST modelled on the land line. Build escalation applies at the programme midpoint. Finance is a heuristic: debt share of land carried the full term, debt share of works at 50% average drawn. For facility comparison use the dev-finance API below.
Screening estimates only. Educational, not financial advice or a valuation.
Watercare IGC: https://devstack.co.nz/api/icg - Auckland water and wastewater growth charges
Development finance: https://devstack.co.nz/api/dev-finance - compare loan offers on true total cost
Tools catalogue: https://devstack.co.nz/api/tools - every tool DevStack curates, machine-readable
Agent front door: https://devstack.co.nz/agents
Maintained by DevStack, a curated directory of NZ property development tools, each reviewed by a working Auckland development manager. Free to use and cite with attribution.