Cardinal numbers

The core pattern (20–99): “unit + und + ten”

German builds most numbers from 21–99 “backwards” compared to English.

• Formula: ones + und + tens
• 21 = ein + und + zwanzig → einundzwanzig
• 34 = vier + und + dreißig → vierunddreißig
• 99 = neun + und + neunzig → neunundneunzig

Self-check: say it like a native listener expects

1. Start with the last digit (ones): 64 → “4 …”
2. Add und: “4 und …”
3. Finish with the tens: “… sechzig”
4. Write it as one word: vierundsechzig

Quick test: If you hear und, you are probably in the 21–99 pattern.

The “eins” exception: why it becomes “ein”

Before a tens number, “eins” changes to “ein”. This is one of the most common mistakes.

• 31: einunddreißig (einsunddreißig)
• 21: einundzwanzig (einsundzwanzig)
• 61: einundsechzig (einsundsechzig)

Tip: Keep eins when it stands alone: eins, Ich habe eins.

Hundert and tausend: stable, no plural, usually no spaces

• 100 = hundert
• 200 = zweihundert (not zwei hundert)
• 1 000 = tausend
• 3 000 = dreitausend

Key point: hundert and tausend do not change form (no plural ending).

Million and Milliarde: noun rules (article + plural)

From a million upward, treat the word as a noun: you need an article for “one”, and plural -en for 2+.

• Correct: Wir haben zwei Millionen Euro.
• Correct: Das Projekt kostet eine Milliarde Euro.
• Wrong: zwei Million / zwei Millionenen

Pronunciation traps that affect spelling

• 30 is dreißig (with ß, not dreizig)
• 60 is sechzig (often the “s” is not clearly heard)
• 70 is siebzig (shorter than “sieben”)

Professional tip: When you write numbers in emails or reports, these three are the most frequent spelling errors.

Mini checklist before you submit an answer

1. Is it ones + und + tens (for 21–99)?
2. Did you use ein (not eins) before the tens?
3. Did you keep hundert / tausend unchanged?
4. For Million/Milliarde: did you add eine for 1 and -en for 2+?