CSAB 2026 Round-wise Seat Matrix — How It Shrinks

The CSAB seat matrix is not a single fixed dataset — it is rebuilt at each round based on what became vacant after the previous stage's reporting concluded. Understanding this cascading structure is the key to understanding why CSAB SR2 typically offers a meaningfully smaller and different set of options than SR1, which in turn is smaller than the original JoSAA matrix.

The process broadly works as follows: JoSAA's own rounds allot seats from the full sanctioned intake across IITs, NITs, IIITs, and GFTIs. After JoSAA's final round concludes and reporting closes, seats that were allotted but never reported against (because candidates didn't show up, withdrew, or were exercising a choice elsewhere) are handed over to CSAB. This handover pool forms the basis of CSAB SR1's seat matrix, restricted to NITs, IIITs, and GFTIs (since IITs and ISM Dhanbad don't participate in CSAB). After SR1 reporting concludes, seats that remain vacant from that round form the basis of CSAB SR2's matrix — a further, and typically smaller, subset.

The table below uses illustrative, rounded example numbers to demonstrate the general shrinking pattern across stages. These figures are not official CSAB 2026 data — they are constructed purely to show the proportional pattern candidates should expect, and actual numbers for any given year can differ substantially. Always check the official CSAB seat matrix published at csab.nic.in for real figures.

* These figures are illustrative only, intended to demonstrate the proportional shrinking pattern. They are not sourced from or intended to represent actual official CSAB 2026 numbers.

The shrinking pattern is not uniform across branches — popular branches shrink faster (proportionally) than less competitive ones, because reporting rates are much higher for in-demand combinations. The table below illustrates this using example proportions, again not official figures:

This pattern is a direct consequence of candidate behavior: candidates allotted a highly desirable branch at a strong institute overwhelmingly tend to report and stay, while candidates allotted less-preferred combinations are more likely to continue seeking upgrades elsewhere or decline, freeing up those specific seats for the next round.

Understanding this round-wise shrinkage pattern is genuinely useful for practical decision-making. If you're participating in SR2, it's realistic to expect a smaller and more constrained set of options than what was visible in SR1 — this argues for filling a broader, more realistic choice list rather than a narrow one built only around top preferences, since the underlying pool you're drawing from has already been substantially depleted of its most popular options.

It also explains why waiting for a hypothetical future round with better options is generally not a sound strategy — each successive round works with a smaller pool, not a fresh or expanded one, so the odds of a dramatically better outcome appearing later in the cycle are structurally lower, not higher.