Goal Attainment Score Calculator
Goal Attainment Scaling (GAS) calculates a standardized T-score from individualized patient or program goals, each weighted by importance and difficulty. A T-score of 50 means goals were met exactly as expected.
Enter up to 5 goals. For each goal, select the attainment level achieved and assign a weight (importance).
Goal 1
Goal 2 (optional)
Goal 3 (optional)
Goal 4 (optional)
Goal 5 (optional)
Typical value is 0.30 (Kiresuk & Sherman, 1968). Range: 0–0.99.
Formula
GAS T-Score (Kiresuk & Sherman, 1968):
T = 50 + 10 × [ Σ(wᵢ · xᵢ) ] / √[ (1 − ρ) · Σwᵢ² + ρ · (Σwᵢ)² ]
- xᵢ = attainment level for goal i: −2 (much less), −1 (less), 0 (expected), +1 (more), +2 (much more)
- wᵢ = weight (importance) assigned to goal i (integer 1–4)
- ρ = estimated inter-goal correlation (default 0.30)
- T = 50 when all goals are met exactly as expected (x = 0 for all goals)
- The formula standardizes the weighted sum to a T-score with mean 50 and SD 10
Assumptions & References
- Goal Attainment Scaling was developed by Kiresuk & Sherman (1968) for evaluating individualized treatment outcomes in mental health settings.
- Each goal is scaled on a 5-point ordinal scale from −2 to +2, with 0 representing the expected (predicted) outcome at the time of goal-setting.
- Weights reflect the relative importance or difficulty of each goal (1 = least important, 4 = most important).
- The inter-goal correlation (ρ = 0.30) is the standard assumption from the original paper; it accounts for the fact that goals within a patient are not fully independent.
- A T-score of 50 indicates goals were met as expected; scores above 50 indicate better-than-expected outcomes; scores below 50 indicate worse-than-expected outcomes.
- GAS is widely used in rehabilitation, occupational therapy, pediatric therapy, and program evaluation.
- Reference: Kiresuk, T.J., & Sherman, R.E. (1968). Goal attainment scaling: A general method for evaluating comprehensive community mental health programs. Community Mental Health Journal, 4(6), 443–453.
- Reference: Kiresuk, T.J., Smith, A., & Cardillo, J.E. (Eds.). (1994). Goal Attainment Scaling: Applications, Theory, and Measurement. Lawrence Erlbaum Associates.
- This calculator is for educational and research purposes only and does not constitute clinical advice.