XtraMath is a free web program that teaches addition, subtraction, multiplication and division facts which are critical to success in mathematics.

 Kindergarten K1K2 K3 K4 K5 
 Grade 1 10 12 1415 18  
 Grade 2 2728 31 3435  
 Grade 3 45 47 4849 51
 Grade 4 36 40 41 42 43 44
                                  Misc.