Gear Ratio
Gear ratio in cycling is the relationship between chainring and cog sizes, determining how far you travel per pedal revolution. Learn how gear ratios affect cadence, speed, and climbing.
Quick Answer
Gear Ratio — is the relationship between the number of teeth on your chainring (front) and cassette cog (rear). A 50/25 combination gives a 2:1 ratio, meaning the rear wheel rotates twice for every pedal revolution. Higher ratios are harder to pedal but faster; lower ratios are easier for climbing.
What is Gear Ratio?
Gear ratio determines how many times your rear wheel rotates for each complete pedal revolution:
Formula:
Gear Ratio = Chainring teeth / Cassette cog teeth
Example:
- Chainring: 50 teeth
- Cassette cog: 25 teeth
- Ratio: 50/25 = 2.0
This means the wheel turns twice per pedal stroke.
Understanding Gear Ratios
High vs Low Ratios
| Ratio Type | Chainring/Cog | Feel | Best For |
|---|---|---|---|
| High (3.0+) | 50/17 | Hard, fast | Flat, descents |
| Medium (2.0-2.5) | 34/17 | Moderate | General riding |
| Low (< 1.5) | 34/28 | Easy, slow | Climbing |
What Ratio Numbers Mean
| Ratio | Wheel Rotations per Pedal Rev | Relative Effort |
|---|---|---|
| 4.0 | 4 rotations | Very hard (descending) |
| 3.0 | 3 rotations | Hard (fast flat) |
| 2.0 | 2 rotations | Moderate |
| 1.0 | 1 rotation | Easy (steep climbing) |
| 0.8 | 0.8 rotations | Very easy (very steep) |
Gear Inches (Alternative Measurement)
Gear inches account for wheel size:
Formula:
Gear Inches = Gear Ratio × Wheel Diameter (inches)
| Gear Inches | Typical Use |
|---|---|
| 20-40 | Steep climbing |
| 40-60 | Moderate terrain |
| 60-80 | Flat cruising |
| 80-100 | Fast flat/descents |
| 100+ | High-speed descents |
Common Gearing Setups
Road Bikes
| Type | Chainrings | Cassette | Gear Range |
|---|---|---|---|
| Compact | 50/34 | 11-28 | 1.21-4.55 |
| Standard | 53/39 | 11-28 | 1.39-4.82 |
| Semi-compact | 52/36 | 11-30 | 1.20-4.73 |
| Wide-range | 50/34 | 11-34 | 1.00-4.55 |
Mountain Bikes
| Type | Chainring | Cassette | Gear Range |
|---|---|---|---|
| 1x12 | 32 | 10-52 | 0.62-3.20 |
| 1x11 | 34 | 10-42 | 0.81-3.40 |
| 2x10 | 38/24 | 11-36 | 0.67-3.45 |
Gravel Bikes
| Type | Chainrings | Cassette | Gear Range |
|---|---|---|---|
| 2x | 46/30 | 11-34 | 0.88-4.18 |
| 1x | 40 | 10-44 | 0.91-4.00 |
Choosing the Right Gearing
Factors to Consider
| Factor | Recommendation |
|---|---|
| Terrain | Hillier = lower gears needed |
| Fitness | Lower fitness = lower gears |
| Cadence | Preferred cadence affects choice |
| Racing | Competition may need higher gears |
| Weight | Heavier riders need lower climbing gears |
Climbing Gear Guidelines
| Gradient | Minimum Gear Ratio |
|---|---|
| 5% | 1.5:1 |
| 8% | 1.2:1 |
| 10% | 1.0:1 |
| 12%+ | < 1.0:1 |
Gear Ratio and Cadence
Gear ratio directly affects cadence at a given speed:
Formula:
Speed = Gear Ratio × Wheel Circumference × Cadence / 60
Example at 90 RPM cadence with 700c wheels:
| Gear Ratio | Speed |
|---|---|
| 2.0 | 24 km/h |
| 2.5 | 30 km/h |
| 3.0 | 36 km/h |
| 3.5 | 42 km/h |
Gear Ratio and Power
| Situation | Gear Strategy |
|---|---|
| Accelerating | Lower gear, higher cadence |
| Steady speed | Middle gear, comfortable cadence |
| Hill start | Very low gear |
| Sprint | Higher gear, lower cadence |
| Into headwind | Lower gear than normal |
Cross-Chaining
Avoid extreme gear combinations:
| Combination | Status |
|---|---|
| Big chainring + big cog | Poor (cross-chaining) |
| Small chainring + small cog | Poor (cross-chaining) |
| Big chainring + middle cogs | Good |
| Small chainring + middle/big cogs | Good |
Cross-chaining causes:
- Increased chain wear
- Drivetrain noise
- Reduced efficiency
1x vs 2x Gearing
| Factor | 1x | 2x |
|---|---|---|
| Simplicity | Simpler, one shifter | More complex |
| Gear range | Narrower (improving) | Wider |
| Weight | Lighter | Heavier |
| Maintenance | Less | More |
| Gear steps | Larger gaps | Smaller gaps |
1x is now standard on mountain bikes and increasingly popular on gravel bikes.
Upgrading Gears
Lower Gearing Options
| Change | Effect |
|---|---|
| Smaller chainring | Lower all ratios |
| Larger cassette | Lower easiest gear |
| Different crankset | New range options |
Higher Gearing Options
| Change | Effect |
|---|---|
| Larger chainring | Higher all ratios |
| Smaller cassette | Higher easiest gear |
| New wheels | Larger diameter = higher effective ratio |
Common Questions
What gearing do pros use?
Typically 53/39 or 54/40 with 11-28 or 11-30 cassettes. However, even pros use compact gearing for very mountainous stages.
Do I need lower gears?
If you're grinding at very low cadence on climbs, struggling on steep sections, or avoiding hills—yes, consider lower gearing.
How do I know my current gearing?
Count teeth on chainrings and cassette, or check manufacturer specs. Cassettes are usually labeled (e.g., 11-28).
What's the "right" cadence for a gear?
Most cyclists are efficient at 80-100 RPM. Choose gears that allow you to stay in this range for your terrain and power output.