Performance Index Explained
Performance Index Explained
The Performance Index (PI) is the sum of three sub-indices — sleep, nutrition, and activity — each scored 1-11 based on how closely you hit your personal targets.
The Three Sub-Indices
| Sub-Index | Data Source | What It Measures |
|---|---|---|
| Sleep Index | Apple HealthKit | Sleep duration relative to your target |
| Nutrition Index | Your food logs | Calorie intake relative to your effective target |
| Activity Index | Apple HealthKit | Active calories burned relative to your baseline |
PI = Sleep Index + Nutrition Index + Activity Index
The result ranges from 3 (all three dimensions at minimum) to 33 (all three at maximum).
How Each Sub-Index Is Scored
Sleep Index uses a floor model. Meeting or exceeding your target gives you the top score. Under-sleeping is penalized proportionally. Oversleeping does not penalize.
| Sleep vs. Target | Index |
|---|---|
| 100% or more | 11 |
| ~75% | 9 |
| ~50% | 6 |
| No data | 1 |
If your target is 7.5 hours and you slept 7.5 (or 9), your sleep index is 11. Sleeping 6 hours (~80%) gives you a 9.
Nutrition Index uses a symmetric model. Under-eating is penalized equally to over-eating — both indicate poor adherence to your planned intake. Precision around your target is what matters.
| Deviation from Target | Index |
|---|---|
| Within 5% | 11 |
| Within 10% | 10 |
| Within 20% | 8 |
| Within 30% | 6 |
| Within 50% | 2 |
| More than 50% | 1 |
If your target is 2,000 kcal and you ate 1,900-2,100 (within 5%), your nutrition index is 11. Eating 1,600 or 2,400 (20% off) drops it to 8.
Activity Index uses an asymmetric model. Exceeding your target is rewarded (up to 150%). Falling short penalizes progressively.
| Activity vs. Target | Index |
|---|---|
| 150% or more | 11 |
| 100% (met target) | 8 |
| 80% | 7 |
| 60% | 6 |
| Below 10% | 1 |
If your activity target is 400 active calories and you burned 400, your index is 8. Burning 600 (150%) gives you 11. Burning 200 (50%) drops to 5.
How to Improve Your PI
Each sub-index improves independently. If your sleep index is dragging your PI down, focus on sleep. The dashboard score card shows each component with color coding: green (9+), amber (6-8), red (below 6). Use this to identify which dimension needs attention.
What this means for you: The Performance Index measures outcomes. The Adherence Multiplier measures behaviors. Together they form your Rubric Score. A PI of 24 with a 3x multiplier produces a score of 72 — a strong day. A PI of 24 with a 1x multiplier produces only 24.
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