One college class is usually between 3 credits and 6 credits per class, depending on the class and the college. Each of those college classes is equivalent to one whole high school credit. College credits are measured differently than high school credits. College credits don't require you to count hours or seat time.
Not all college classes are 3-6 college credits, though. If a class doesn't fit within that area, then high schools have some discretion on how many credits are awarded. That means that YOU, homeschoolers, also have some discretion. Below 3 college credits, a public school might give 1/2 high school credit, and sometimes lower, even 1/4 credit. I usually suggest that a college class that is 3-6 credits is worth 1 high school credit. And any college class that is 1-2 credits would get 1/2 high school credit.
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You might feel more confident if you saw this it in print from a government agency. In Washington State, for example, they spell out the public school policy very clearly here:
(2) College and university course work. At the college or university level, five quarter or three semester hours shall equal 1.0 high school credit: Provided, That for the purpose of this subsection, "college and university course work" means course work that generally is designated 100 level or above by the college or university.