Skip to McMaster Navigation Skip to Site Navigation Skip to main content
McMaster logo

Frequently Asked Questions


Read the error message carefully and refer below to the correct next steps.

Available seats are reserved, and you do not meet the reserve capacity criteria.

  • A certain number of seats in each course and each section are reserved for students in specific programs, so the section may appear to have space, but the seats are not available to everyone. For example, Bio 1A03 will have a certain number of seats reserved for students in Biochemical Engineering, Science Level One, and the Arts and Science program. If you are a Science Level One student but the only seats left in the section you are attempting to enroll in are reserved for Arts and Science students, you will need to choose a different lecture section in order to register.
  • If this is an elective course, these seats have been filled. You can try another section or keep checking back on Mosaic to see if a seat has opened or choose another available elective.
  • If it is a required course for your degree completion and all sections are closed, please contact the department or school directly.

Unable to add this class – requisites have not been met.

  • Check the Undergraduate Calendar to ensure you meet the prerequisites for the course. If you meet all listed prerequisites and you are still receiving this error then contact our office.
  • If you are a Level 1 course that has a lab, please ensure you enrol in WHMIS 1A00 and BIOSAFE 1BS0 first, as they are co-requisites for certain courses with a lab component

No Results – There are no schedule combination(s) with the selected courses.

  • You have searched for courses that are scheduled at the same time during the week. You cannot enrol in courses that are held at the same time. Use the checkbox left of each course to toggle it on or off and explore your options.
  • For all first-year students enrolled in Chemical & Physical Sciences, Environmental & Earth Sciences, Life Science and Mathematics & Statistics, you have a great deal of flexibility in choosing your courses as long as you meet your Level I program requirements. The choices you make often depend on the admission requirements of your intended Level II program.
  • For all first-year Honours Kinesiology students, you have a great deal of flexibility in choosing your elective courses. It is important to read the Program Notes section in the Undergraduate Calendar because some of your choices may be influenced by the Honours Bachelor of Science Kinesiology program requirements.
  • All first-year Medical Radiation Sciences students are allowed to take 6 units of electives. It is important to read the Program Notes section in the Undergraduate Calendar because your choices may be influenced by the Bachelor of Medical Radiation Sciences program requirements.
  • Many Level I courses are open to everyone; however, some courses have requisites, which means you must meet certain conditions in order to enrol in them. For example, you may have to have a specific U/M, or be enrolled in a certain program (e.g. Engineering I). Or you may not be allowed to take a course if you have already completed a particular U/M or university course. Other courses may only be taken if you have already completed a preceding McMaster course. Sometimes, you must be enrolled in or have completed another university course to be able to take a certain course. Be sure to consult in the Course Listings section of the Undergraduate Calendar beneath each course description, to check whether the course you want has any prerequisites, antirequisites or corequisites.

Yes. Students can use either the Class Search or MyTimetable function in Mosaic to ensure that the combination of courses that they have selected can be scheduled free of conflicts.

  • Your course load should be balanced between the Fall Term (September to December) and Winter Term (January to April). For most students this means taking 15 units each term.
  • Please be aware that you do NOT have to carry a full coarse load. However, if you are considering reducing your load, it is important to speak with an Academic Advisor so that you can be made aware of the effects that a reduced load may have (e.g., Athletics, bus pass, scholarships, residence, OSAP, etc).
  • To be considered a full-time student during the Fall/Winter, you must be registered in at least 9 units per term.

Yes. You will enrol for courses for the full academic year (both Fall and Winter Terms).

  • Required courses are all courses that are specifically designated for inclusion in a program. For example, all first-year Mathematics & Statistics students must take MATH 1B03.
  • Elective courses are those courses taken by a student which are not specifically designated in a student’s program, but which form a part of the total number of units required to complete the program. Elective courses may be chosen from courses outside the Faculty of Science, as long as the requisites to take that course are met.
  • A list of Elective Courses Available to Level I Students is available in the online academic calendar.
  • All McMaster courses have a fixed number of seats available. If there is a blue square icon next to the course, it is full. Please choose a different course or section.
  • Sometimes there may be a green circle next to the course but you are getting an error message that the course is full. This means the empty seats are reserved for a specific group of students (i.e. program). If those seats do not fill, they may be released in August.
  • If the course is a requirement of your program, please contact the department for assistance.
  • Prerequisite: A requirement that must be fulfilled before enrollment in a course is permitted.
    • Example: BIOLOGY 1A03
      Prerequisite: Grade 12 Biology U or BIOLOGY 1P03 and enrollment in any Level I program in the Faculty of Science
  • Co-requisite: A course which must be taken together with another course
    • Example: CHEM 1A03
      Co-requisite: WHMIS 1A00 if not already completed
  • Anti-requisite: A course which cannot be taken before, after or at the same time as the course with which it is listed
    • Example: MATH 1X03
      Anti-requisite: ARTSSCI 1D06, MATH 1A03, 1LS3, 1N03, 1ZA3, 1Z04

Yes. All McMaster courses have a fixed number of seats available, which are filled on a first-come, first-served basis. Therefore, you should not to delay your enrollment if you are very keen to get into specific courses. If the course is already full, you will see a blue square icon on Mosaic immediately, letting you know you need to make an alternative selection. If your course is a requirement of your program, please contact us for further information.

  • If you decide that you want to make changes to your timetable, you may do so by the last day of the Drop/Add period each term without penalty. Note throughout the Academic Year, there are three terms: Fall Term, from September to December; Winter Term, from January to April; and Spring/Summer Term, from May to August.
  • You cannot enrol in courses after the last day of Drop/Add. Cancelling a course after this date will result in a notation of ‘W’ (Withdrawn) on your transcript and cancellation charges as outlined on the Office of the Registrar website will apply.
  • To drop a course before the last day of the Drop/Add period go to your Mosaic Student Center > Enroll > Drop > Select the term > Check off the course you would like to drop > Select Drop Selected Classes > Finish Dropping.
    drop using MyTimetable.
    1. Click the trash can beside the course you want to drop
    2. Scroll down and click Get this Schedule
    3. On the next page scroll down and click Do Actions.
  • If you are dropping a course and want to add another course – use the “Swap” option! That way you won’t be dropped from the course until you are added to the new course.


  • Academic advisors are always available to assist you with any problems or questions you may have regarding your course selections and changes to your enrollment. Throughout the year, we can also provide you with information about the McMaster Student Absence Form (MSAF), exams, taking courses at another university (for credit at McMaster), Petitions for Special Consideration, and more. If you are struggling for any reason or need help, don’t wait. Come to see us for help right away. For information about drop-in academic advising hours, please see the Contact Us page.
  • Or you can email us at

In the Faculty of Science, there are a few courses you may be required to take that are zero unit courses. These courses are not calculated into your course load or course count. WHMIS 1A00 (SCIENCE 1A00) is an example of a zero unit course.

  • You can tell how many units a course is worth by looking at the final digit(s) in the course code. For example, SOCIOL 1A06 is worth 6 units and runs from September to April. PHYSICS 1A03 is worth 3 units and will run either September to December or January to April.
  • The first digit in the course code indicates the level of the course (I, II, III or IV).
  • Your academic level is determined by the number of courses you have successfully completed.

Level I:  0 – 21 units

Level II:  24 – 51 units

Level III:  54 – 81 units

Level IV: 84+ units

  • Admission to a Level II program will depend on your academic performance in Level I as well as the courses you have taken. You will need to have taken the required courses – as outlined in the online Faculty of Science Programs and Degrees section of the Undergraduate Calendar. Admission averages vary from year to year, depending on the number of applicants.
  • Entrance to a non-limited enrollment, 4-year Honours B.Sc. program requires a minimum Cumulative Average (CA) of at least 5.0, with specific course requirements and minimum grades in particular courses, as outlined in the Faculty of Science Programs and Degrees section of the Undergraduate Calendar.
  • Entrance to a 3-year B.Sc. program requires a minimum Cumulative Average (CA) of at least 3.5, with an average of at least 4.0 (C-) in the required subject courses.
  • Please note that admission to our limited enrollment programs is competitive and is based on academic achievement in Level I. Possession of the published minimum requirements does not guarantee admission.
  • No. Combinations of subjects from the Faculty of Science and other faculties at McMaster are not possible, apart from the designated Combined Honours B.Sc. programs such as Honours Biology & Mathematics, Honours Biology & Environmental Sciences, Honours Biology & Psychology, Neuroscience & Behaviour, Honours Mathematics & Computer Science, and Honours Mathematics & Physics already offered by the Faculty of Science.
  • Your Cumulative Grade Point Average (GPA) is a weighted average based on the grades obtained in all of the courses that you have taken at McMaster University.
  • To calculate your Cumulative Average, you multiply the grade received in a course by the number of units in this course. Use this formula for each course you have completed. Then, add these numbers up and divide this total by the total number of units. This number is your GPA.
  • To find out more about the grading system used at McMaster and to see an example of how the Cumulative GPA is calculated, go to the Grading System section of the Office of the Registrar website.
  • A Minor is declared as you prepare for graduation. For more information, please see the Graduation Information page.
  • For a list of Minors available in the Faculty of Science, please visit the Faculty of Science section of the Undergraduate Calendar.
  • Please visit the Lab Safety Courses page for information about the WHMIS 1A00 and HTHSCI 1BS0 courses.

Career & Experiential Learning

  • Co-operative education or Co-op is an academic program that alternates academic semesters with periods of full-time work experience. Selection to all 12 of our co-op programs is based on academic achievement and an interview. Although entry to a co-op program doesn’t begin until Level III, in your first year, it is a good idea to review the co-op program admission requirements in the Programs (by Degree) and Minors section of the Undergraduate Calendar to ensure you are on track with program admission requirements.
  • In Level II, you should plan to attend a co-op information session in January. All applications are due in March. Information about our co-op programs and the selection procedure may be obtained from our Science Career and Co-operative Education Office.
  • If you are considering applying to a co-op program, you should enrol SCIENCE 2C00 in Level II. This is a non-credit, tuition-free course for Science students that provides an opportunity for you to develop the career skills necessary to create a career path in the Science field.