Free Gear Ratio & FTP Cycling Calculator

Not directly — it depends on whether you are already at your cadence ceiling.

When the answer is yes: if you are spinning out — hitting the top of your cadence range in your current gear — then a bigger gear is the only way to go faster. There is no other option at that point.

Mechanical efficiency: bigger gears are genuinely little more efficient. The chain bends less sharply around larger sprockets, reducing friction losses. This matters most at the small end — cogs smaller than 13 teeth are disproportionately inefficient because the chain articulation angle becomes severe, wasting measurably more watts per pedal stroke.

Power = cadence vs force: For the same power output: shifting to a bigger gear without spinning out simply slows your cadence. Lower cadence means more force per stroke, which recruits fast-twitch fibres and accelerates muscular fatigue. On a long ride, that cost typically outweighs any mechanical efficiency gain from the larger sprocket.

The right answer: the fastest gear is the one that keeps you in an efficient cadence range (80–100 RPM on flat and rolling terrain) while avoiding very small cogs. Bigger is only better when you've genuinely run out of cadence headroom.

Lower gears let you pedal with less force per stroke — and that's the foundation of endurance riding.

Muscular fatigue: Grinding a big gear at 60–70 RPM recruits fast-twitch muscle fibres that fatigue quickly and accumulate metabolic waste. Shifting to a lower gear and spinning at 85–95 RPM moves the same power through smaller, repeated contractions — relying more on slow-twitch fibres that recover continuously. On a 3–5 hour ride, this difference compounds dramatically. The legs that feel fine at hour two tell a very different story at hour four if you've been mashing.

Joint preservation: Lower gears reduce peak force on the knee with every pedal stroke. Climbing in too big a gear puts extreme stress on the patellofemoral joint, quad tendon, and IT band. Keeping force low and cadence high is the most effective way to protect knees over a long season — particularly on steep climbs where torque is highest.

Bailout gears: When power drops late in a ride or on a steep climb, having a low enough gear means you can keep spinning at reduced output instead of grinding to a stop. A rider with a 34×32 can keep the cranks turning at 60 RPM on a 15% grade with minimal power — a rider with a 39×25 cannot. The ability to keep moving at low power is what gets you to the top of a climb without putting a foot down.

Freshness in the final hours: Riders who use appropriately low gears throughout conserve muscular integrity for the end of the ride. The compact crankset (50/34 or 46/30) and wide cassette philosophy used by endurance cyclists is precisely about minimising muscular strain early so power remains available late.

The highest-impact improvements in order:

1) Aerodynamics — reducing CdA (position, clothing, equipment) cuts drag, which scales with the square of speed and accounts for 80–90% of resistance above 30 km/h. At 20 km/h it's already the dominant force; at 40 km/h it's overwhelming. The faster you ride, the more aero matters.

2) Tires — switching to lower rolling resistance tires (lower Crr) saves watts at any speed, for free.

3) Weight — losing body weight (which is ~80% of the system) meaningfully reduces both gravity and rolling resistance on climbs. On flat ground the effect is negligible, but on steep gradients it's one of the most effective levers available.

4) Gears — gearing is rarely a performance limiter by itself, but wrong gear selection forces a poor cadence and wastes energy. Gears become a hard constraint when the cassette doesn't offer enough ratio for a given climb or sprint — at that point, no amount of fitness overcomes a mechanical ceiling. A dirty or poorly lubricated drivetrain adds further losses: a worn, dry chain can waste 3–5W compared to a clean, well-lubed one — free speed that requires only a rag and a bottle of lube.

On flat ground at 30 km/h, saving 1 kg of bike weight gives roughly 0.05 km/h — essentially nothing. On an 8% climb at 10 km/h, it's worth about 0.3 km/h. Here's the key nuance: the bike accounts for only ~20% of total system weight, while the rider is ~80%. Losing 1 kg of body weight has the exact same physics effect as a 1 kg lighter bike — but it's far more achievable for most cyclists. On climbs, reducing rider weight is one of the most effective strategies available.

Yes — significantly. The coefficient of rolling resistance (Crr) measures how much energy the tire wastes per meter rolled. Upgrading from a typical training tire (Crr ≈ 0.006) to a high-performance race tire (Crr ≈ 0.003) saves roughly 5–10 watts at 30 km/h, translating to 1–2 km/h of free speed.

Tire pressure is equally important — and completely free. Too low and the tire deforms excessively, wasting energy; too high and the tire bounces over road imperfections instead of absorbing them, which also increases rolling resistance on real surfaces.

Aerodynamics is more important on virtually any terrain above about 15 km/h. Air drag scales with the cube of speed — double your speed and drag power increases eightfold. At 30 km/h on flat ground, a 10% reduction in CdA (e.g., lowering your head and tucking your elbows) saves roughly 15–20W. Dropping 2 kg of bike weight on the same flat saves less than 1W.

Weight only wins on long, steep climbs — the crossover is roughly above 7–8% gradient at speeds below 15 km/h, where gravity dominates and aerodynamic drag becomes negligible.

For a typical setup — 75 kg rider, 8 kg bike, CdA of 0.35, Crr of 0.006, flat road, no wind:

20 km/h (12 mph) → ~65 W  |  40 km/h (25 mph) → ~350 W

Double the speed, but roughly 5–6× the power. That gap is almost entirely explained by aerodynamic drag, which scales with the cube of speed — double your speed and drag power increases eightfold. At 20 km/h, aero drag accounts for ~57% of total resistance; at 40 km/h it's over 85%. Use the calculator above to model your exact setup.

Not directly — for the same gear and cadence, speed is identical regardless of crank length. The gains are indirect: a shorter crank reduces hip flexion at the top of the stroke, which can unlock a lower, more aerodynamic position — a real speed gain on road and gravel. For XC mountain bikers, shorter cranks also mean fewer pedal strikes on technical terrain, allowing more speed through rock gardens and tight corners. Use the gain ratio in the calculator to see how crank length interacts with your gearing.

Gain ratio is a dimensionless number expressing the complete mechanical advantage of your drivetrain — chainring, cog, and crank arm length all in one figure. A gain ratio of 4.0 means every millimetre your foot travels around the pedal arc produces 4 mm of forward wheel movement.

Unlike gear ratio (teeth only) or gear inches (imperial, ignores crank length), gain ratio is directly comparable across any bike, wheel size, or crank length. A 170 mm crank at 50×17 and a 172.5 mm crank at 50×17 have identical gear ratios but different gain ratios — and therefore different effective gearing.

Concept introduced by Sheldon Brown. This calculator displays gain ratio for every gear combination.

Only if you also increase power. Cadence alone does not determine speed — speed is the product of cadence, gear ratio, and wheel circumference. Spinning faster in the same gear produces more speed, but that requires more power. If your power stays the same, shifting to a higher cadence means shifting to a smaller gear to maintain the same speed, not going faster.

Where cadence matters is efficiency and fatigue: a higher cadence shifts effort from muscles to the cardiovascular system, which recovers faster. Most trained cyclists target 80–100 RPM as the range that best balances muscular and cardiovascular load over time.

There is no universally ideal cadence — the right number is whichever one minimises your total fatigue at a given power output. That balance point is individual and shifts with fitness.

The underlying physiology: low cadence means fewer, more forceful pedal strokes — heavily muscular. High cadence means more strokes at lower force — heavily cardiovascular. Your body unconsciously finds an equilibrium between the two. Marsh & Martin (1997) showed that cyclists are more economical at their freely chosen cadence than at any cadence imposed above or below it. You self-optimise without trying.

What changes with fitness: as aerobic capacity grows, the cardiovascular cost of higher cadence falls. Trained cyclists naturally gravitate toward 85–100 RPM not because someone told them to, but because the muscular savings at higher cadence outweigh the added cardio load for a fit rider. The coaching convention of "80–100 RPM" is an observation of what trained cyclists self-select — not a prescription.

Practical takeaway: don't force a target. If you're new, ride at what feels natural — cadence will rise as fitness develops. If you're experienced and grinding at 65 RPM on flat ground, experimenting with slightly higher cadence may reduce leg fatigue by the end of a long ride, even if it feels harder cardiovascularly at first.

That said, discipline and terrain do shift where the natural equilibrium lands:

• Road — flat & rolling: 80–100 RPM — balances efficiency and fatigue; higher cadence offloads work to the cardiovascular system.
• Road — climbing: 65–80 RPM — torque demand naturally lowers cadence; forcing higher is cardiovascularly costly.
• XC MTB — smooth: 70–90 RPM — slightly lower than road; traction and bike control take priority.
• XC MTB — loose or steep climbs: 55–75 RPM — traction-limited; too high a cadence spins the rear wheel out.
• Sprinting: 110–130+ RPM — short enough that muscle fatigue isn't a concern.

The gauge uses yellow for the climbing/XC range and green for the road sweet spot.

Roughly twice the power — gradient is a near-linear relationship. A 70 kg rider + 8 kg bike producing 280W climbs a 10% grade at ~12 km/h. On a 20% grade at the same power, speed drops to ~6.5 km/h — half the speed, same effort. Double the gradient, double the required power at any given speed. Mass works the same way: 10% heavier means ~10% more climbing power. Neither relationship compounds.

At 7.5 km/h on a standard compact 34×32, cadence drops to ~48 RPM. That is a grind! Standup pedeling. A gravel-style wide-range cassette 30x36 lets you hold ~60 RPM. The difference is whether you reach the top under fatigue or on muscle failure.

Constrat that to aerodynamic drag, which scales with the cube of velocity — going twice as fast requires theoretically 8× the drag power.

FTP (Functional Threshold Power) is the maximum power output a rider can sustain for approximately one hour. It is the fundamental ceiling on your sustainable speed — higher FTP means you can ride faster on any terrain for longer. On flat roads, a rider with 250W FTP will cruise at around 35 km/h; a 300W rider at roughly 38 km/h (same aero setup). Raising FTP through training is the only long-term speed lever.

FTP is often expressed as W/kg (watts per kilogram of body weight) to compare riders of different sizes and predict climbing performance. A 250W FTP at 75 kg = 3.3 W/kg. Tour de France GC contenders typically sustain 5.8–6.2 W/kg at threshold on major climbs. W/kg determines climbing speed far more than absolute watts — a lighter rider with the same FTP climbs significantly faster.

CdA is the product of the drag coefficient (Cd) and the rider's frontal area (A). It is the single number that captures how aerodynamic a rider-bike system is. A lower CdA means less air resistance at any speed. Typical values: ~0.45 for an upright mountain biker, ~0.35 for a road cyclist in the drops, ~0.20–0.25 for a time trialist on aero bars. CdA can be reduced by changing position, wearing tighter clothing, or using aerodynamic equipment.

Look up your exact tire on BicycleRollingResistance.com — the most comprehensive database of real-world tire tests, with results at multiple pressures.

Note that they publish results in Watts, not as a Crr coefficient. That wattage is what appears as BRR in the rolling resistance slider of this calculator — so you can read the number directly from their site and match it to the BRR value shown.

There are four approaches, in order of cost and precision:

• Estimate from position (free): use the typical values in the CdA slider — ~0.45 upright, ~0.35 road drops, ~0.20–0.25 TT bars. Accurate enough for most training and setup decisions.
• Virtual Elevation / Chung method (free): ride a flat loop, record power + GPS, then back-calculate CdA using software like Golden Cheetah or Aerotune. Requires a calm day and careful protocol, but gives a real number for your actual position.
• Aero sensor (mid cost): devices like Notio or AeroSensor mount to the bike and measure drag in real time during any outdoor ride — good for comparing positions without a lab.
• Wind tunnel (high cost): gold standard, ~€500–2000 per session. Used by pros and serious amateurs for definitive position optimization.

For most riders, the Chung method gives 90% of the value for free. The key insight: even a rough CdA estimate dramatically improves the calculator's power predictions versus leaving it at the default.

The case for the pack: a 2 L bladder with a pack weighs roughly 2.5 kg when full — about 3% of a typical 83 kg system (rider + bike + gear). Use the weight sliders above to see exactly what that costs on your target gradient and power: add 2.5 kg to the payload and watch the speed change. That penalty shrinks continuously as you drink. Against that, every aid station stop is dead time at zero speed, and stops introduce execution risk — crowding, understocking, or a poorly timed approach can cost far more than the weight ever would.

The case for aid stations: starting without a pack means lower system weight from the gun — you are faster on every climb right up to the first stop. Aid stations also let you refuel food alongside fluids. On shorter courses with well-placed stations, the pack weight is never fully recovered by the time the finish line arrives.

Practical rule: for races under 60–75 minutes, a bottle on the frame is usually enough. For longer races in heat, a pack almost always wins. The right answer depends heavily on how much fluid you actually need — use the Fuel Plan calculator to get an accurate estimate based on your intensity and duration before deciding.