The Hitchhiker's Guide to Dutch Mortgages

Solo vs Couple × 10/15/20/30y annuity. All math in your browser. Hover any underlined label for an explanation. Modelling tool, not advice.

Houses cost a kidney and your bank's calculator doesn't explain why. Every Dutch bank gives you a different "max mortgage" with no breakdown, half the vocabulary is in Dutch (NHG, kosten koper, hypotheekrenteaftrek, startersvrijstelling…), and somehow you're supposed to just vibe a 30-year decision.

This tool lays out 8 setups side-by-side — solo or with a partner, locked in for 10 / 15 / 20 / 30 years — and shows what each one actually costs per month, in total interest, and after the tax refund. Tweak the price, your salary, your age, sub-rent a room. Watch all eight numbers move in real time.

No login. No email. No "request a quote." Just math, in your browser. Built because I needed it myself.

1. Your financials

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2. Partner financials

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3. House

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4. Mortgage rates (NHG, April 2026 defaults)

5. Sub-rent (kamerverhuur) — tax-free up to € 6.633 / yr

The kamerverhuurvrijstelling (KVV) lets you collect up to € 6.633 / year from renting a room in your owner-occupied home completely tax-free — no income tax, the rented portion stays in Box 1. Cliff edge: earn even €1 over → the entire amount becomes taxable at 37,56 % Box 1 (not just the excess), and the rented share may shift to Box 3.

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6. Extra repayment

Scenario comparison — 8 setups side by side

How is "viability" computed?
✓ Viable = mortgage stays within Nibud LTI bounds AND usable cash covers closing costs. The LTI uses the official Nibud 2026 financieringslastpercentage table at the chosen rate over a 30-year looptijd, plus the single-buyer extra (€17k, solo only) and the energy-label bonus — matches the Excel workbook. Cash short = closing costs (KK + transfer tax if applicable) exceed your usable cash.

Per-scenario amortisation breakdown

How to read the chart: bars and cost lines use the LEFT axis (€ per year you spend); the emerald line uses the RIGHT axis (€ of loan still owed — a much bigger range).

Each year you pay a fixed monthly amount to the bank. That amount splits into: loan repayment (cyan, shrinks your debt) + interest (magenta, the bank's profit). The full bar = total cash sent to the bank that year. The Dutch tax office refunds part of the interest (the HRA — hypotheekrenteaftrek); the dashed yellow line shows what you actually pay after that refund. If you rent out a room, the dotted violet line subtracts that rent income too. Year by year the yellow line creeps closer to the bar top — less interest paid = less HRA refund.

Sources: NHG limit €470k / premium 0.4% (NHG.nl 2026), startersvrijstelling cap €555k under-35 (Belastingdienst), OVB 2% standard, Box 1 brackets 35.75% / 37.56% / 49.50%, HRA cap 37.56%, EWF 0.35% × WOZ, KK fixed €4,800, KVV cap €6,633, single-buyer extra €17k (2026). Annuity payments via PMT; cumulative principal/interest via CUMPRINC/CUMIPMT (re-implemented in JS).