A/L Z-Score Calculator Sri Lanka

Enter your mark, the subject mean, and the subject standard deviation for each of your three subjects to calculate your Z-score. The mean and standard deviation change every year, subject, and medium, so take them from the figures the Department of Examinations publishes with your results.

These mean and standard deviation values are indicative, not official

The Department of Examinations works out the Z-score itself and prints it on your result sheet; it does not publish the subject mean and standard deviation behind it. The presets below are typical figures for each stream, useful for estimating before results or for seeing what a mark is worth — but a Z-score built from them is an estimate, not your official one. Replace any field with the real figure if you have it.

Already have your Z-score? Check it against the 2025/2026 university cut-offs.

Load a stream:

Your Z-score

1.3611

The average of your three subject z-scores

Subject by subject

  • Combined Mathematics

    72 against a mean of 45, +27 marks

    +1.3500

  • Physics

    65 against a mean of 42, +23 marks

    +1.5333

  • Chemistry

    58 against a mean of 40, +18 marks

    +1.2000

Your strongest subject by z-score is Physics, which is not necessarily your highest mark — a lower mark on a harder paper can be worth more.

How places are allocated

Every course splits its intake three ways, which is why the Z-score needed differs by district.

  • 40%

    All-island merit

    Ranked on Z-score alone, across every district.

  • 55%

    District quota

    Allocated to the 25 districts in proportion to population, then ranked within each district.

  • 5%

    Educationally disadvantaged districts

    Reserved for districts identified as educationally disadvantaged, allocated on population.

Why a raw mark cannot be compared across subjects

A 70 in one subject and a 70 in another are not the same achievement, because papers differ in difficulty and cohorts differ in strength. Ranking candidates on raw marks would reward whoever happened to sit the easier paper.

The Z-score removes that by measuring each mark against how everyone else did on the same paper. A z of 0 is exactly average, a z of 1 is one standard deviation above the field, and a z of -1 is one below.

The same mark can be worth very different z-scores
MarkSubject meanStandard deviationz
757010+0.50
755010+2.50
603510+2.50
607010-1.00

The three subject z-scores are averaged, not added

A candidate's Z-score is the arithmetic mean of their three subject z-scores. Adding them instead would triple the figure and produce a number that does not match any published cut-off.

A candidate scoring z-scores of 1.0, 0.5 and 0.0 has a Z-score of 0.5. Because it is a mean, one weak subject drags the whole figure down by a third of its shortfall, which is why balance across three subjects matters more than a single outstanding result.

Where the mean and standard deviation come from

The Department of Examinations publishes the mean and standard deviation for every subject, broken down by medium of instruction, alongside each year's results. They are not constants: they move with the difficulty of the paper and the composition of the cohort.

Using a previous year's figures will give a wrong answer, sometimes by a wide margin. That is why this calculator asks for them rather than storing a table that would silently go stale.

  • Check that the figures match your medium of instruction, not just your subject.
  • Sinhala, Tamil, and English medium candidates are standardised separately.
  • A subject sat by a small cohort can have a much larger standard deviation.

How places are actually allocated

The Z-score is the input to a selection process, not the selection itself. Every course splits its intake three ways, and the cut-off differs across them, which is why two candidates with the same Z-score can get different outcomes.

How the places on a course are divided
StreamShareRanked on
All-island merit40%Z-score alone, across every district
District quota55%Z-score within your district, allocated on population
Educationally disadvantaged5%Reserved districts, allocated on population
  • District allocations follow population, not the number of candidates or how well they did.
  • A district with fewer strong applicants can therefore admit on a lower Z-score.
  • Cut-offs are published by the UGC after results are processed, never before.

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Frequently asked questions

Each subject is standardised on its own: z equals your mark minus the subject mean, divided by the subject standard deviation. Your Z-score is then the arithmetic mean of those three subject z-scores, not their sum. A z of 0 means you scored exactly the subject average; a z of 1 means one standard deviation above it.

Papers differ in difficulty from subject to subject and year to year, so a 70 in one subject is not the same achievement as a 70 in another. Standardising against how everyone else sat the same paper makes candidates in different subject streams comparable, which is what an island-wide ranking needs.

The Department of Examinations publishes them alongside each year's results, broken down by subject and medium of instruction. They are not fixed values - they move every year with the difficulty of the paper and the composition of the cohort, so a figure from a previous year will give you a wrong answer.

Yes, and it happens often. A 75 in a subject where the mean was 70 is worth less than a 60 in a subject where the mean was 35, because the second result is much further above the field. This is exactly what the Z-score is designed to capture.

No. Selection depends on the cut-off for the specific course, your district, and which of the three quotas you are competing under, and cut-offs are only published after the whole cohort's results are processed. This calculator gives you the Z-score itself, which is the input to that process.

40% of the places on every course are filled on all-island Z-score rank alone. A further 55% are shared among the 25 districts in proportion to population and ranked within each district, and the last 5% is reserved for districts identified as educationally disadvantaged. Because district allocations are population-based rather than performance-based, the cut-off for the same course varies considerably between districts.

There is no fixed good score - it only means something against the cut-off for the course and district you are applying to. A Z-score that comfortably enters one course can fall short for a more competitive one in the same district, which is why the cut-off checker is the tool that answers this.

Yes, and it is not unusual. A negative Z-score simply means the mark sat below the mean for that subject in that sitting. Because the three subject scores are averaged, a strong result in the other two can still pull the overall figure back up.