Our students start timed math facts tests the first month of school. It is too early for some and they have no idea what to do. The first one is the benchmark (which is the end of the year test) to see what they know and still need to work on. Every month for progress monitoring I have to use the end of the year test, but use the leveled test in between to help the kids master the level that they are working on.
They have to be able to pass a 25 question facts to/from 18 test, with 85% or higher by the end of the year. They get 5 minutes to complete these. There are levels that they have to complete starting with facts to/from 8, then it moves up to facts to/from 18.
My second graders have to complete a 50 question mixed facts to/from 20 test by the end of the year.
In between these I use the timed math facts tests from the back of the Evan Moor Basic Math Skills book. I also have One Minute Math books that I can use.
If you have a subscription to enchantedlearning, abcteach, or edhelper, you can make your own math facts timed tests.
Here are a few math websites that might have timed math tests:
personally I don't think 1st graders are developmentally ready for timed math facts tests, but I have to give them.