⟨oo⟩ Pronunciation Rules

The spelling ⟨oo⟩ causes confusion for learners of English pronunciation because it is commonly pronounced as both short /ʊ/ and long /uː/, though there isn’t a rule to indicate which pronunciation should be used. Additionally there are a handful of ⟨oo⟩ words that are neither /ʊ/ or /uː/. Some words with this spelling are pronounced with /ʌ/, /ɔː/ and even /əʊ/. 

The problem for most learners is that the spelling looks like a long vowel sound because it has two vowels. The logical place to start learning then, is with those words that are not long, those pronounced with short /ʊ/:

book /bʊk/
brook /brʊk/
cook /kʊk/
cookie /ˈkʊki/
foot /fʊt/
good /ɡʊd/
hood /hʊd/
hook /hʊk/
look /lʊk/
rook /rʊk/
shook /ʃʊk/
stood /stʊd/
took /tʊk/
understood /ʌndəˈstʊd/
whoosh /wʊʃ/
wood /wʊd/
wooden /ˈwʊdᵊn/
wool /wʊl/
woollen /ˈwʊlən/

Most other words are pronounced /uː/, however there are a few more alternatives that also need to be learnt. Words pronounced with /ʌ/:

blood /blʌd/
flood /flʌd/

Words pronounced with /ɔː/ (always spelt ⟨oor⟩):

floor /flɔː/
door /dɔː/
poor /pɔː/ (also /pʊə/)
moor /mɔː/ (also /mʊə/)

And the word ‘brooch’, which is a one-off, it’s pronounced with diphthong /əʊ/:

brooch /brəʊtʃ/

This leaves the largest group of ⟨oo⟩ words, those pronounced with /uː/, which includes:

balloon /bəˈluːn/
boot /buːt/
choose /tʃuːz/
fool /fuːl/
goose /ɡuːs/
igloo /ˈɪɡluː/
mood /muːd/
moot /muːt/
school /skuːl/
scoop /skuːp/
shoot /ʃuːt/
soon /suːn/
swoop /swuːp/
tool /tuːl/
voodoo /ˈvuːduː/
zoom /zuːm/