Open composite index methodology

Last reviewed: 22 July 2026

Some of our tools are open composite indices — single 0–100 scores built from several inputs. The whole point is that they are transparent: we publish the inputs, how each is scored, the weights, and the evidence behind them. You can reconstruct any score yourself. That openness is the opposite of the hidden scores inside proprietary wearables and testing services.

How a score is built

  1. Sub-scores (0–100). Each input becomes a 0–100 sub-score where higher is always more favourable, via a documented, clamped linear mapping between stated anchor points.
  2. Weights and evidence tiers. Weights sum to 100%. Every input is tagged T1 (strong, outcome-linked evidence), T2 (moderate/surrogate) or T3 (mechanistic). No single input exceeds ~30%, and a weak (T3) input never outweighs a strong (T1) one.
  3. Aggregation.The index is the weighted average of the sub-scores. Some tools also show a centred “pace” number, which is just a display transform of the same index.
  4. Missing data. Leave an input blank and the weights renormalise across what you provided, with a reduced-confidence flag — we never substitute a value that flatters or penalises you.

What these scores are not

A composite index here is a transparent tool for self-tracking. It is not a medical test and has not been validated against health outcomes. No index outputs a mortality estimate, life-expectancy figure or disease probability; body- composition inputs are capped and never dominate; and none produces medication or supplement advice. A low sub-score points to a modifiable lever — it is never a judgement on you.

Versioning & changelog

Weights and mappings are part of the public contract: they never change silently. Every change bumps the version and is recorded here.

Written and reviewed by Mathew Beale — MSc Biotechnology, University of Reading.

Last reviewed: