Free tools
Calculators for people who train hard
Free, no sign-up, no email gate. Each one runs the same engine that powers the Fuelog app, so the numbers you get here are the numbers you get in your pocket.
Why these are free, and where the numbers come from
Nobody should have to install an app to find out whether its maths is any good. These calculators run the exact same TypeScript module that ships inside Fuelog — copied across verbatim rather than reimplemented, so the site and the app cannot quietly disagree with each other. Every figure is either a published guideline or a constant you can see the effect of by moving a slider.
What the calculators will not do
They will not hand you a carbohydrate rate you have never practised. Absorption capacity is trainable and it is the one input here you cannot fake, so the race plan caps at the rate you enter and then tells you roughly how many weeks the ramp to a higher one would take — about +10 g/h every two and a half weeks of deliberate practice on your long session. If the race is too close to close the gap, it says so rather than quietly optimising a plan you cannot execute.
What the app adds
A calculator plans one race. Inside the app the same engine reads your training load from Whoop, Garmin or Apple Watch and moves carbohydrate between 3 and 12 g/kg a day, scaled by whether you are in base, build, peak or taper. It tracks energy availability against your fat-free mass, opens the carb-load window 36–48 hours out, and raises the race plan every time your trained tolerance goes up.
Educational tools, not medical or dietary advice. Never try a new fueling plan for the first time on race day.