The Explanatory Note to the 1997 Office Memorandum gives the method for constructing a roster in a single sentence. It is worth understanding, because it explains the shape of the table and lets you sanity-check any roster you are handed. It also does not, by itself, reproduce the published roster — and knowing where it stops is the difference between checking your work and trusting a generator that is quietly wrong.
The rule
The Explanatory Note states it plainly: the method for making a roster is to multiply each post by the prescribed percentages of reservation for the different reserved categories, and the point at which the multiple for a community obtains a complete number or oversteps the number is to be reserved for that community.
Put as a formula: the n-th point of a category with percentage p is the smallest whole number P at which P × p reaches or passes n.
Applying it to the first point of each category in the open-competition roster:
- OBC at 27 per cent — 1 ÷ 0.27 = 3.7, so the first OBC point is 4.
- SC at 15 per cent — 1 ÷ 0.15 = 6.67, so the first SC point is 7.
- EWS at 10 per cent — 1 ÷ 0.10 = 10, so the first EWS point is 10.
- ST at 7.5 per cent — 1 ÷ 0.075 = 13.33, so the first ST point is 14.
All four match the published table. So far the rule works.
Where it stops working: collisions
SC at fifteen per cent is exactly double ST at seven and a half per cent. That is not a coincidence of the figures — it is a structural feature, and it means that every ST claim lands on a point that an SC claim also wants. The second SC point and the first ST point both compute to 14. The fourth SC point and the second ST point both compute to 28. And so on, all the way down.
Something has to give, and the Explanatory Note shows the resolution by example rather than by rule: at point 15 both OBC and SC become entitled, but because the immediately preceding reserved point had gone to the OBCs, point 15 is reserved for SC and point 16 for OBC. The loser of a collision is displaced to the next free point.
The difficulty is that the order in which those collisions resolve does not follow a single mechanical rule that reproduces the table. Checked against the published roster, the raw formula accounts for 84 of the 119 reserved points and leaves 35 unexplained — every one of them a point that became reserved because a displaced category landed on it. The observed sequence of SC-versus-ST collision winners runs ST, SC, ST, SC, SC, ST, SC, SC, ST and onwards, which is not a pattern that any fixed priority order produces.
And squeezing
Near the 100 and 200 boundaries the displacement runs backwards rather than forwards, so that each block of a hundred contains exactly the whole-number quota for every category. This is why points 98, 99 and 100 are EWS, SC and OBC respectively, and why the run from 196 to 200 is EWS, OBC, ST, SC, OBC.
The Supreme Court Registry's own published version of the model roster marks precisely these points with asterisks and the note that squeezing has been resorted to in order to maintain the prescribed percentage of reservation. The 2019 Office Memorandum uses the same term when explaining how EWS points were fitted in.
What this means in practice
Use the published table. Do not compute the roster. The formula is a good way to understand the structure and to check whether a given point looks plausible, but it will not reproduce the Office Memorandum, and a roster that differs from the Office Memorandum is wrong however elegant the arithmetic behind it.
If you come across a roster generator that claims to compute points from the percentages, check its output against the Annexure before relying on it. The two will diverge.
The Reservation Roster Trainer uses the published table as its answer key for exactly this reason, and its reference tab reproduces both model rosters point by point.
What the model roster contains
Over 200 points, for direct recruitment on an all-India basis by open competition: 30 SC, 15 ST, 54 OBC, 20 EWS and 81 unreserved. That is exactly 15, 7.5, 27 and 10 per cent, with 40.5 per cent unreserved.
For a cadre of any given strength, you read the roster from point 1 down to the cadre strength. A cadre of 40 posts uses points 1 to 40; the SC points within that range are 7, 15, 20, 27 and 35, which is five, and 40 × 15 per cent = 6.0 — so the roster gives five where the arithmetic gives six. That kind of small divergence at a particular cadre size is normal and is a consequence of where the points happen to fall; the two converge as the cadre grows, and it is the roster that governs.
Checking a roster you have been handed
Three checks catch most problems quickly.
Count the categories against the cadre strength. Multiply the strength by each percentage, ignore fractions, and compare with the number of points of that category in the roster you are looking at. Small differences at particular cadre sizes are expected; large ones are not. Check the first points. In the open-competition roster the sequence begins UR, UR, UR, OBC at 4, then UR, UR, SC at 7, OBC at 8, UR, EWS at 10. If the roster in front of you starts differently, either it is a different mode of recruitment, or it is a different roster altogether — the Railway roster, for instance, places its first SC point at 4. Check the mode. Annexure-II is open competition; Annexure-IV is otherwise than by open competition and begins to diverge from point 13. Promotion is a separate roster with only SC and ST in it.Frequently Asked Questions (FAQ)
Q1. Can I generate the roster in a spreadsheet from the percentages?
Not reliably. The formula gives you the earliest point each category is entitled to, but it does not resolve collisions in the way the published table does, and it does not reproduce the squeezing near the 100 and 200 boundaries. Checked against the Office Memorandum, the raw formula leaves 35 of the 119 reserved points unexplained. Use the published table.
Q2. Why does every ST point collide with an SC point?
Because 15 per cent is exactly twice 7.5 per cent, so the arithmetic that generates the SC points generates the ST points at every second SC threshold. The first ST point and the second SC point both compute to 14, and the pattern repeats throughout the roster.
Q3. Our cadre is 40 posts. The roster gives 5 SC points but 40 times 15 per cent is 6. Which is right?
The roster. Entitlement at a particular cadre strength depends on where the points happen to fall within the first N points of the roster, and small divergences from the raw percentage are expected at particular sizes. They even out as the cadre grows — over the full 200 points the roster gives exactly 15 per cent.
Q4. Does the same roster apply to every Central Government department?
No. Following the Supreme Court order of 27 November 2024, Indian Railways applies the roster table in the Indian Railway Establishment Manual rather than the DoPT model roster, implemented by Railway Board RBE No. 17/2025. The tables differ from the first points onward.
Related Reading
Next: operating the roster — the register columns, recasting, and what happens when a post falls vacant. You can practise building a roster in the Reservation Roster Trainer.