Free guide · university admission
What is a Z-score?
The number on your A/L results sheet that decides which state university course you can get. What it measures, how it is worked out, and what to do with yours.
The short answer
Your Z-score compares you with everyone who sat the same subjects in the same year. In each subject it measures how far your mark was above or below the average, in units of that subject's spread (its standard deviation). Your final Z-score is the average of your three subjects. That way a hard paper and an easy paper are put on the same scale, and a student is not punished for choosing a subject that was marked harshly that year.
සරලවම, Z-score එකෙන් පෙන්නන්නේ ඒ අවුරුද්දේ ඒ subject එක ලියපු අනිත් හැමෝටම වඩා ඔයා කොච්චර ඉස්සරහින්ද පස්සෙන්ද කියලා. subject තුනේම Z-score වල සාමාන්යය තමයි ඔයාගේ final Z-score එක.
How it is calculated
For each subject:
z = (your mark − subject average) ÷ subject standard deviation
Then:
Z-score = (z₁ + z₂ + z₃) ÷ 3
A Z-score of 0 is exactly average. Positive is above average, negative is below. Most students fall between about −2 and +2, and a Z-score above 2 is rare.
A worked example
The numbers below are invented to show the method. Real averages and standard deviations change every year and are not published before results.
| Subject | Mark | Avg | SD | z |
|---|---|---|---|---|
| S1 | 72 | 50 | 18 | 1.2222 |
| S2 | 65 | 48 | 17 | 1.0000 |
| S3 | 58 | 45 | 15 | 0.8667 |
| Z-score (average of the three) | 1.0296 | |||
Why your district matters
Selection uses your Z-score together with the district you sat the exam from. Many places on each course are allocated district by district, so the same course has a different cut-off in every district, and some courses are filled on island-wide merit alone. That is why a Z-score that reached Medicine in one district may not have reached it in another.
See every course's cut-off in every district: Z-score cut-offs by course.
Have your Z-score? See what it reached
Every course your stream can apply for, against last round's cut-off in your district. Free, no sign-in.
Common questions about the Z-score
What is a Z-score in A/L?
A number that shows how far your result in each subject was above or below the average of everyone who sat that subject in the same year, measured in standard deviations. Your final Z-score is the average of your three subjects' Z-scores. It is printed on your results sheet.
Can I calculate my Z-score from my marks?
Not in advance. You need each subject's island-wide average and standard deviation for that year, and those are not published before results. Online calculators that take raw marks are guessing those numbers.
Is a Z-score of 1 good?
It means you were one standard deviation above the average across your three subjects — well above the middle. Whether it is enough depends on the course and your district. Compare it with last round's cut-off for the courses you want.
Why does the same course need a different Z-score in each district?
Many university places are allocated district by district, so each district has its own competition and its own cut-off. That is why the UGC publishes one cut-off per course, per university, per district.
Why do cut-offs change every year?
A cut-off is simply the Z-score of the last student selected. It moves with how many students applied, how they performed, how many places there are and the order students put the courses in. Last year's cut-off is a guide, not a promise.
More for the move to university
- After A/L — what to do while you wait
- Z-score cut-offs for every course
- UGC application guide — dates and course order
- Free checker — last round's cut-offs in your district
- Campus Match — your chance at every course
- Free first-year guides — email, APA, AI rules
- Campus Ready for parents
- Campus Survival Pack — templates and guides