Futter
An endurance fuelling planner for iPhone and Mac. Futter turns the session you’re about to do into three numbers, carbohydrate, fluid, and sodium, tells you when to take them, and then shows you how to make the same fuel yourself for about a fifteenth of what gels cost.
2026 – Today
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Design, Research, Development
Introduction
Futter is a native iOS and macOS app, built in SwiftUI, for hobby athletes who suspect they’re under-fuelling, not for pros with a coach. Tell it your sport, how long, and how hard, and it works out how many grams of carbohydrate, how much fluid, and how much sodium you need per hour. Then it gives you the recipe to mix it at home from maltodextrin, fructose, and table salt. It’s offline-first, with no account, no email, and no analytics.
The goals
On long rides and runs, most people fade because of what they ate, not because of how fit they are. Your muscles hold about ninety minutes of hard effort; after that, what keeps you going is what you take in. The free fuelling planners out there are mostly funnels for selling gels, and gels are expensive. I wanted a planner that gives an honest answer for the session you’re actually doing, explains where every number comes from, and then tells you to make the stuff yourself.
Three numbers for the session you’re actually doing: carbs, fluid, and sodium
Make the DIY recipe the heart of the app, and keep it free forever
Read the route, not just the clock, from a GPX file or a ride in Health
Trace every figure back to the research behind it
Guide, never alarm: guardrails as calm information, never restriction
Ask for nothing: no account, no analytics, offline-first
Research
Futter gives nutrition guidance, so the numbers had to be inspectable and provable before anything else. I started from the published research and wrote a calculation spec that defines every number the app produces, with reference test cases it has to satisfy. Three questions shaped it:
Where do the numbers come from? Published guidance: Jeukendrup on carbohydrate intake, the ACSM position stand, Baker on sweat rate and sodium, and the international consensus on exercise-associated hyponatremia.
How does the route change the plan? Published energy models, Minetti for running and Martin for cycling, turn the climbing into effort, so two hours on the flat and two hours up the Schöckl get different answers.
Why should anyone trust it? The math is pure Swift: deterministic, dependency-free functions covered by unit tests. And the app says when not to fuel, too, and where drinking more stops being safer.
Process
Futter should feel like a good notebook, not a dashboard: a warm off-white ground, rounded type, and generous corners. Its voice is for someone with cold hands at a trailhead, not a sports scientist. A few design decisions carry it:
Plain language: effort is “you could chat in short sentences”, never “76–83% of threshold”.
Numbers wear ink: carbs, fluid, and sodium each have a colour, validated with a colour-vision checker, but the value itself is always set in text colour.
One answer per screen: only the carbohydrate figure floats; fluid and sodium are ranges you keep an eye on.
Calm guardrails: a caution is sand, not red, so 90 g an hour reads as the top of the normal range, not an emergency.
More room, more columns: on the Mac and iPad, a wider window adds columns rather than stretching the cards.
Under the hood, Futter is offline-first: the product catalogue and ingredient data ship with the app, plans are stored on the device, and the only network calls, a catalogue refresh and iCloud sync, are opt-in. Nothing read from Health ever leaves the device that read it.
Solution
Futter turns a planned session into a fuelling plan: carbohydrate per hour with a cadence like “20 g every 20 min”, fluid and sodium as ranges, and a timeline of when to eat. Then it tells you to make it yourself. The same fuelling you’d buy as gels costs about a fifteenth as much made at home, and Futter gives you the recipe, the amounts, the ingredient swaps, and what it costs against the shop price. That recipe is the reason the app exists, so it’s free and always will be.
Prefer to buy? The product picker does the packing maths for whatever is already in your drawer. Import a GPX file or pick a ride you’ve recorded in Health, and Futter plans from the climbing instead of the duration. Six short reads explain what your body does with fuel, each traced back to its research.
On the Mac, Futter spreads out. The plan, the recipe, and the products sit side by side in one window, so you can change the session on the left and watch the numbers and the shopping list follow on the right. Plans sync between iPhone and Mac through iCloud, so a ride planned at the desk is already in your pocket at the trailhead.
Futter is coming soon to the App Store for iPhone and Mac. Everything you need to fuel a session is free, without time limits or nagging. Futter Pro adds route intelligence beyond your first imported route, a sweat test that measures your own rate, and a gut-training programme, for €2.99 a month, €24.99 a year, or €59.99 once. It’s guidance, not medical advice.