The 3x or 4x income rule appears in almost every Dutch listing, and the one detail that decides whether an applicant clears it — gross or net — is rarely spelled out. People who guess wrong rule themselves out of places they could have applied for, or waste a viewing on one they never had a chance at.
Almost always gross, not net — and no, that's not landlords trying to trick you, it's just the convention, though it's worth confirming explicitly before you get your hopes up about a place. The multiplier itself varies by risk appetite: private landlords often ask 3x, agencies and larger verhuurders sometimes push to 4x or even 5x. The logic is about their downside, not your budget — a vacant month is roughly a twelfth of their annual return, and evicting a non-paying tenant requires a court procedure that can drag on for months, so they're pricing in that risk rather than calculating what you can actually afford. NIBUD, the Dutch budgeting institute, reckons 3x is already generous cover, since the standard rule of thumb caps housing costs at a third of income. If you're just under the bar, it's worth asking whether they'll count a partner's income, savings, or a guarantor instead of walking away.