Why is 21 written as eenentwintig?

Dutch puts the unit before the ten and joins them with -en-, so 21 is een-en-twintig, written as one word eenentwintig. The same pattern gives vijfenveertig for 45 and negenennegentig for 99. This inversion is one of the most distinctive features of Dutch numbers.

What is the trema in tweeëntwintig?

When the unit ends in -e and is followed by the -en- connector, Dutch adds a trema to keep the vowels apart. So 22 is tweeëntwintig and 23 is drieëntwintig, with the ë marking a new syllable. The tool applies this automatically.

When are numbers written as one word?

Numbers up to and including the thousands are written closed up, so honderd, duizend, tweeduizendvierhonderd are single words. The scale words miljoen and miljard are separate words, written as een miljoen, twee miljard, and so on.

How large a number can it handle?

It spells values up to 999 trillion (999.999.999.999.999) using miljoen, miljard, and biljoen. Above that the result is not shown, since everyday Dutch rarely needs larger written-out numbers.

Is anything sent to a server?

No. The conversion runs entirely in your browser with a local algorithm. Nothing is uploaded, so it is safe to use for private figures.

Dutch Number to Words

Email me this result

Get this tool's output sent to your inbox, plus one useful tool a week. No spam, unsubscribe any time.

This tool writes whole numbers in Dutch words. Dutch number spelling has a few features that trip up learners and software alike, especially the unit-before-ten order and the trema, so the tool encodes the real rules rather than a rough mapping.

How it works

The algorithm builds the word from the smallest parts up. Within each group of three digits it handles units, the inverted tens, and hundreds, then joins the thousand, million, and billion scales:

Inversion with -en-: the unit comes first, joined to the ten by en, so 45 is vijf + en + veertig = vijfenveertig.
Trema: when the unit ends in -e, the connector takes a trema, so 22 is tweeëntwintig and 23 is drieëntwintig.
Closed-up scales: honderd and duizend join without a space and drop the leading een when they stand alone, so 100 is honderd and 1000 is duizend, but 200 is tweehonderd.
Separate scale words: miljoen and miljard are written as separate words with een, so 1.000.000 is een miljoen.

21        -> eenentwintig
22        -> tweeëntwintig
200       -> tweehonderd
1.000.000 -> een miljoen

Tips and notes

You can type Dutch-style thousands separators (dots) and they are ignored, so 1.000.000 and 1000000 give the same result. The tool spells cardinal numbers; for ordinals such as eerste, tweede, or negentiende, use the Dutch ordinal words tool. Written-out numbers are common in formal Dutch for amounts on cheques and contracts, where the inversion and trema matter for correctness.