Skip to content
RUNNERS LAB

Energy and fueling calculators

Running calories, race energy, carbohydrate targets, gels, fuel timelines, and caffeine timing estimates.

Last reviewed 26 August 2026

Energy tools estimate calories from ACSM running VO2 and body mass, then scale that burn across a distance or race. Per-kilometre and per-mile pages lock the distance headline on the same engine.

Fueling tools turn race duration into carbohydrate grams per hour using ISSN/ACSM-style bands, then into gel counts and even fuel timelines. Caffeine timing reports a published milligram-per-kilogram range and a pre-race window.

Every page on this category is an estimate, not medical advice, and not a personalised nutrition plan. Heat, gut tolerance, and product labels are not in the math. Citations live on the methodology page.