The inputs
Fuel Snapshot's target is built from five things: your sport, your goal for the session (Easy, Perform, or Race), your body weight, the session's duration, and, optionally, a route's elevation gain from an uploaded GPX file.
Duration and goal set the base range
The starting carbohydrate-per-hour range is looked up from your session's duration and your chosen goal. Longer sessions and higher-intensity goals both push the range upward — a short Easy session and a long Race effort sit at opposite ends of the scale, with Perform in between.
Sport-specific adjustment
Different sports carry a modifier on top of the base range, reflecting typical differences in how demanding an hour of that sport tends to be at a given intensity.
Weight adjustment
Body weight nudges the range slightly — a small increase for heavier athletes, a small decrease for lighter ones, within a defined band where the adjustment doesn't apply at all, since weight alone is a coarse proxy and only worth a modest correction.
Route elevation
If you upload a GPX route, its total elevation gain can add a bonus on top of the range, capped at a maximum that depends on your goal — a harder goal allows a larger cap, but the bonus is always capped, not open-ended, since more climbing raises demand only up to a point that a flat calculation can usefully capture.
What comes out
The result is a g/h range and a total for the session, along with a plain-language explanation of why the need is what it is, and a few typical, concrete ways to hit that number with real products. Add a barcode-scanned or manually entered product, and Fuel Snapshot checks it against the target and helps place it on a timeline for the session.
Where the product data comes from
Barcode lookups pull from Open Food Facts, a public, crowd-sourced nutrition database, read per serving rather than per 100 g so multipacks and serving sizes are handled correctly. Photographed nutrition labels or manual entry cover products that aren't in that database.
What this is not
- Not a machine-learning model. There's no training data or prediction involved — it's a fixed calculation, and the same inputs always give the same output.
- Not personalized medical or clinical advice. It doesn't know your medical history or current health status, and isn't a substitute for a doctor, dietitian, or coach — particularly for anyone managing a medical condition.
- Not aware of day-to-day variables like heat, illness, sleep, or how you specifically feel that day. The range is a starting point, and real-world experience should adjust where you sit within it.
Who built this, and how it's reviewed
Fuel Snapshot's fueling rules were built by the team behind the app, based on the same general endurance-nutrition ranges referenced throughout this site's guides — duration- and intensity-based carbohydrate ranges, and the idea that longer or harder efforts need more, and can tolerate more when spread across multiple carbohydrate sources. This page will be updated if the underlying rules change.