I have been asked a few times now about coffee grounds pH and their impact on the soil. During my research, I came across a good fact sheet from MSU, and you can find the link to learn more about pH levels and coffee grounds here.
As I’ve mentioned in my post The Ground to Ground Primer – Coffee Grounds for the Garden:
Used coffee grounds are slightly acidic, with a range typically between 6.9pH and 6.2pH. It would be higher except that most of the acid within the beans is extracted during brewing.
For many vegetable and ornamental plants, the desirable pH range is 6.9 to 5.8. A pH level of 7.0 is considered neutral, and from there it is increasing in alkalinity.
So you will find that there are very few situations where the slightly acidic nature of coffee grounds are going to be a problem, especially as most of it should be going into the compost and the rest straight into the garden.
I have heard of concerns with coffee grounds going into small pots, the type for indoor plants. If you are going to add them into pots, make sure you dig the grinds into the soil and avoid it just sitting on the top. Coffee grounds will form a top crust if left that way, blocking water and air movement.
If there are any problems with the link, you can find the PDF below.
Coffee Grounds for Plants According to pH
- Mould and coffee grounds (groundtoground.org)
- How does the chemical properties of the soil relate to soil fertility (wiki.answers.com)
Ground to Ground 
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