German numbers aren't a random list to memorize one by one — they follow a clear, logical pattern that you'll need constantly: giving your age, paying for something, sharing a phone number, booking an appointment. Learning the pattern once saves you from memorizing every number separately.
From zero to twelve, the numbers are independent words with no shared logic, so just learn them as they are: null, eins, zwei, drei, vier, fünf, sechs, sieben, acht, neun, zehn, elf, zwölf. From 13 to 19, the rule is simple: take the single digit and add zehn ("-teen"), as in vierzehn (14 = four + ten). Watch for two small irregularities: sechzehn (16) drops the s from sechs, and siebzehn (17) drops the last syllable of sieben.
The tens from 20 to 90 have their own endings (zwanzig, dreißig, vierzig...), and here comes the key part: compound numbers between 21 and 99 are built ones-before-tens. The number 21 is einundzwanzig — literally "one-and-twenty" — with the unit spoken before the ten, the same order many languages use when saying numbers aloud, just written as one fused word with no spaces: ein+und+zwanzig, rather than three separate words.
If your own language already says the unit before the ten, this pattern will feel familiar — you mostly just need to learn the words and glue them into one compound word. For prices, the number goes directly before Euro, with no plural -s no matter how large the number: fünfzehn Euro (15 euros). Phone numbers, though, are read digit by digit rather than as one large compound number, because a mistake there is more costly: null-eins-sieben... spoken one digit at a time, not as if reading a number in the millions.
Two mistakes are especially common: forgetting to fuse the compound number into a single word and writing it as separate words instead, or mixing up sechs (six), sechzehn (16), and sechzig (60), since they share the same first syllable and differ only in the ending — a trap that catches beginners especially in fast spoken German.