How We Calculate

Every calculator on this site is based on published rules and public data. This page explains which sources we use, how often we check them, and what the tools can and cannot do.

Calculation rules & data sources

All calculators use the official rules and rates for 2026. The main sources per topic:

  • NibudLending standards (financieringslastnormen) behind the maximum mortgage calculation
  • NHGCost limit (€470,000; €498,200 with energy measures) and premium rules
  • Belastingdienst / RijksoverheidTransfer tax, first-time buyer exemption (≤ €555,000), mortgage interest deduction (37.56%), eigenwoningforfait, gift tax exemptions
  • CBS / Kadaster / NVMTransaction prices per m², overbidding percentages per city and neighbourhood, market developments
  • RVO / Milieu CentraalISDE subsidy amounts and indicative costs and savings of energy measures
  • Municipal tax regulations2026 rates for property tax (OZB), waste collection and sewerage charges

Each calculator shows its own "About this calculation" section with the specific rules and sources for that tool.

How we keep the numbers current

  • Lending standards, tax rules and NHG limits are updated when the new annual rules are published (typically towards January 1st) and re-checked during the year.
  • Market data (prices per m², overbidding percentages) is based on CBS/Kadaster/NVM figures and refreshed periodically.
  • The current check date is shown on each calculator. Last full check: July 2026.

Independence

  • HouseGuide is free, requires no account, and does not sell your data or leads. All calculations run locally in your browser.
  • No lender, broker or other commercial party influences the outcomes of the calculators.
  • The site is a personal project by Martijn Minderhoud, funded by voluntary donations. Read more about the creator →
What the tools are — and are not
All outcomes are indicative. Your actual borrowing capacity, costs and conditions depend on your personal situation and the policies of individual lenders. The tools do not constitute financial advice; for binding calculations, consult a certified mortgage advisor.

Spotted an error?

Found an outdated rate or an incorrect calculation? Please let us know — corrections are usually live within a few days. feedback@huiskoopwijzer.nl