LSAT, GPA, and the Law School Admissions Index Formula

What the Admissions Index Is

Every law school that uses LSAC’s Credential Assembly Service receives an “admissions index” for each applicant — a single composite number computed from LSAT and GPA using a formula the school configures privately in LSAC’s ACES2 system. This index appears at the top of every applicant’s CAS report and is often used to sort or screen applications before holistic review begins.

The General Formula

Index = A × LSAT + B × GPA + C

Where A, B, and C are constants set by each school. Schools choose their own weights, typically through LSAC’s formula selection tool, based on their enrollment goals and historical data.

Example: Columbia Law School

One of the few published examples (from admissions consulting research):

Columbia Index = 0.016 × LSAT + 0.242 × GPA − 0.284

For a 173 LSAT / 3.92 GPA applicant (at Columbia’s median):

= 0.016(173) + 0.242(3.92) − 0.284
= 2.768 + 0.949 − 0.284
= 3.433

Columbia’s historical 25th/50th percentile index scores: approximately 3.35 / 3.43.

Why LSAT Is Weighted More Heavily

Rankings incentive: US News & World Report’s law school rankings weight median LSAT heavily. Schools that maximize their median LSAT move up in rankings. This creates a direct financial incentive to favor LSAT over GPA.

Standardization: GPA comes from thousands of different institutions with wildly varying grading standards. A 3.8 from an Ivy means something different than a 3.8 from a school with grade inflation. The LSAT is a single standardized test, making it a more comparable data point across applicants.

Predictive validity: Research suggests the LSAT-GPA combination predicts first-year law school grades better than GPA alone. The LSAT is specifically designed to assess legal reasoning skills.

Typical T14 LSAT weight: 60–70%. Berkeley is an outlier, historically weighting GPA at ~61%.

CAS GPA vs. Transcript GPA

LSAC’s CAS recalculates GPA with specific rules:

• All undergraduate institutions included (no school is excluded)
• All attempts at a course count (grade forgiveness and repeat policies are ignored)
• Grades standardized to A=4.0, A-=3.67, B+=3.33 etc.
• Pre-college credits (AP, IB, dual enrollment) excluded

The CAS GPA is almost always lower than the applicant’s institutional GPA. Enter CAS GPA in this calculator, not your transcript GPA.

Index Score as a Screening Tool

Many schools use the index for initial screening — applicants below a threshold may receive less thorough review or earlier decisions. Above the threshold, the full holistic review begins: personal statement quality, letters of recommendation, work experience, diversity factors, and demonstrated interest all contribute.

The index is a starting point, not a decision. A borderline index with exceptional softs (compelling personal statement, high-profile employment, strong LOR from a recognized figure in law) can still result in admission. Similarly, a strong index with weak softs can still result in rejection.