About Woonsom

A free calculator that puts the main Dutch mortgage and tax rules for 2026 in one place, in English and Dutch.

Why it exists

Comparing mortgage options in the Netherlands means combining loan maths with tax rules that change every year: the interest deduction, the notional rental value, transfer tax, NHG, and for rental homes the choice between box 3 and a BV. Most calculators cover one of these at a time, and few work in English. This one lets you compare options side by side before you speak to an adviser.

Who is behind it

Woonsom is built and maintained by Woonsom.

Independent and ad-free

The calculator is not affiliated with any bank, lender, mortgage adviser or tax adviser. It shows no advertising and earns nothing from the choices you make.

How it is kept up to date

The rules are reviewed when the government publishes its tax plans each September and again when new rules take effect on 1 January. The rules were last checked on 21 September 2026. You can read exactly what the calculator applies on How it works.

Your privacy

Your figures stay in your browser. There are no tracking cookies and no analytics. Read the privacy statement for details.

Get in touch

Questions, a result that looks wrong, or an idea for a feature? Send a message.