The Netherlands: leave scales with your working days, and 8% arrives in May
The Netherlands has its own quirk that this tool does not model: an 8% holiday allowance paid on top of salary, usually in May. A Dutch salary of 50,000 is worth about 54,000 once it is counted. Dutch job adverts are inconsistent about whether the quoted figure includes it, so the first question to ask about any Dutch offer is whether the number is inclusief or exclusief vakantiegeld, the answer moves the real hourly rate by 8%.
Statutory leave is not a fixed number of days. It is four times your weekly working days, so a five-day week earns 20 days, a four-day week earns 16, and part-time work scales without anyone having to negotiate it.
Public holidays are the other trap. Dutch law does not guarantee that they are paid at all; whether you get King's Day off with pay depends on your contract or your sector's collective agreement. The figure here is therefore set to zero rather than to a national count, which makes the Dutch rate per hour worked look closer to the headline rate than in neighbouring countries.
Full-time is also not settled at 40. Between 36 and 40 hours is normal, and plenty of Dutch contracts call 36 hours full-time, an 11% difference in the hourly rate on the same salary, which is why the hours field is worth setting to your own contract rather than accepting the default. The Working Hours Act caps the average at 48 and sets no premium for the hours between; any supplement comes from the sector agreement.