What vowel sound does the O in 'to' make?

Answer 1

Properly, the O in to is a long U or OO sound, the same as too or two.

However, many US speakers colloquially use a "tuh" sound rather than "too" and both pronunciations may be used interchangably, without distinction, by the same individual speakers.

Answer 2

The O in 'to' makes a short vowel sound, similar to the 'ah' sound in the word 'hot'.