What math facts should a 4th grader know?

Keep the times tables quick, multiply and divide bigger numbers, and find factor pairs.

By the end of 4th grade

Add and subtract multi-digit whole numbers fluently with the standard algorithm. (4.NBT.B.4)
Multiply a number of up to four digits by a one-digit number, and multiply two two-digit numbers. (4.NBT.B.5)
Divide numbers of up to four digits by a one-digit number, with remainders. (4.NBT.B.6)
Find all factor pairs of a whole number from 1 to 100, and tell whether it is prime or composite. (4.OA.B.4)

These come from the Common Core State Standards for Mathematics, which most US states use or have adapted. Your child's school may word them differently.

What that looks like

Times tables stay quick, because multi-digit multiplication and division lean on them at every step.
Factor pairs: 36 = 1 × 36 = 2 × 18 = 3 × 12 = 4 × 9 = 6 × 6.
Prime or composite: 37 has no factor pair except 1 × 37, so it's prime.

How to practice at home

A few minutes a day works better than a long session once a week.

1-minute multiplication test
1-minute division test
Divisibility rules
Mental math tricks (multiply by 5, 9 and 25)

Take the 1-minute division test

Common questions

How long should my child practice math facts each day?

A few minutes a day is enough for most kids. Short, regular practice sticks better than a long session once a week.

My child still counts on their fingers. Is that a problem?

Counting is a normal step on the way to knowing facts from memory. Strategies like making a 10 bridge the gap, and a 1-minute test shows which facts are still slow.