Gel Comparison Tool

How to choose a running gel

Three factors matter: carb density, carb source ratio, and gut tolerance. Carb density determines how many packets you carry and open during a race. A 50g gel means fewer packets than a 22g gel. Fewer packets means less fumbling, less trash, and less chance of dropping one.

Carb source ratio matters above 60g/hr. Your gut absorbs glucose and fructose through different transporters. A gel with a 1:0.8 or 2:1 glucose-to-fructose ratio uses both pathways, allowing absorption rates above 60g/hr that a glucose-only gel cannot match. This is the science behind the dual-transporter model (Jentjens et al. 2004).

Gut tolerance is personal. Some runners handle thick gels fine. Others need liquid formulas or hydrogels. The only way to know is to test during training, not on race day. Start with the gel you plan to race with at least 4-6 weeks out and practice taking it at race pace. For more on this, read our guide to the science of race fueling.

Why carbs per dollar matters

Gels add up fast. If you're training with gels twice a week over a 16-week marathon block, cost per serving compounds quickly. Carbs per dollar is the metric that captures this—it tells you how much fuel you actually get for your money, regardless of packet size or brand. Carbs Fuel at $2 for 50g leads the field. SiS Beta Fuel delivers 40g for $3.49. At the other end, Maurten Gel 160 gives you 40g for $5.50.

Glucose-fructose ratio explained

Your small intestine absorbs glucose through SGLT1 transporters, which max out around 60g/hr. Fructose uses a separate transporter (GLUT5). By combining both sugars, you can absorb 90-120g/hr—the target range for competitive marathon fueling. Gels with a 1:0.8 or 2:1 glucose-to-fructose ratio are designed for this. Gels that list only maltodextrin (a glucose chain) will cap your absorption at 60g/hr, which is fine for half marathons but leaves performance on the table for full marathons and ultras.

When to use caffeinated gels

Caffeine improves endurance performance at doses of 3-6mg per kg of body weight. For a 70 kg runner, that's 210-420mg total. The key is timing: save caffeinated gels for the back half of your race when perceived effort climbs and focus fades. Taking them too early wastes the boost when you don't need it and risks GI issues on top of the carb load. Popular caffeinated options include Precision PF 30 Caffeinated (100mg), Maurten Caf 100 (100mg), and Neversecond C30+ (75mg).

For in-depth reviews of each gel, read our Best Race Day Gels 2026 guide. Ready to build your race-day plan? Use the fueling calculator to get a minute-by-minute gel schedule.