Bicycle Gear Ratio Calculator

Calculate gear ratios, gear inches, and expected speeds for your bicycle’s gearing setup. This calculator helps cyclists optimize their gearing for different riding conditions and performance goals.

How to Use This Calculator

1. Enter your chainring (front) teeth count
2. Input your cassette (rear) teeth count
3. Specify your wheel size
4. Add your typical cadence (pedaling speed)
5. The calculator will provide:
   • Gear ratio
   • Gear inches
   • Speed at given cadence
   • Development meters

Understanding Bicycle Gearing

Gear Ratio

The gear ratio is the relationship between the number of teeth on the front chainring and the rear sprocket. A higher ratio means harder pedaling but higher potential speed.

Common Gear Ratios

• Climbing: 1:1 to 1.5:1
• Flat terrain: 2:1 to 3:1
• Descending: 3:1 to 4:1

Gear Inches

Gear inches represent the equivalent diameter of a direct-drive wheel that would give the same mechanical advantage. This measurement helps compare different gear combinations across different wheel sizes.

Wheel Sizes and Measurements

Common Wheel Sizes

• Road bikes: 700c (622mm)
• Mountain bikes: 26” (559mm), 27.5” (584mm), 29” (622mm)
• BMX: 20” (406mm)
• Folding bikes: 16” (349mm), 20” (406mm)

Tire Considerations

• Wider tires increase effective wheel diameter
• Consider adding 2x tire width to wheel diameter
• Account for tire compression under load

Cadence Guidelines

Typical Cadence Ranges

• Casual riding: 60-80 RPM
• Efficient riding: 80-90 RPM
• Performance riding: 90-100 RPM
• Racing: 95-105 RPM
• Sprinting: 110+ RPM

Factors Affecting Optimal Cadence

• Rider fitness
• Terrain
• Riding style
• Event type
• Personal preference

Gearing Recommendations

Road Cycling

1. Flat Terrain

   • Chainring: 50-53T
   • Cassette: 11-28T
   • Common ratios: 2.5:1 to 3.5:1

2. Hilly Terrain

   • Chainring: 46-50T
   • Cassette: 11-32T
   • Common ratios: 1.5:1 to 3:1

3. Mountain Climbing

   • Chainring: 34-36T
   • Cassette: 28-34T
   • Common ratios: 1:1 to 1.5:1

Mountain Biking

1. Cross-Country

   • Chainring: 32-34T
   • Cassette: 10-50T
   • Common ratios: 0.7:1 to 3:1

2. Trail/Enduro

   • Chainring: 30-32T
   • Cassette: 10-51T
   • Common ratios: 0.6:1 to 3:1

3. Downhill

   • Chainring: 34-36T
   • Cassette: 11-28T
   • Common ratios: 1.2:1 to 3.5:1

Speed Calculations

Factors Affecting Speed

• Gear ratio
• Wheel size
• Cadence
• Rider power
• Wind resistance
• Road conditions
• Gradient

Speed Formula

Speed (mph) = (Wheel Circumference × Cadence × Gear Ratio × 60) ÷ (63360)

• Wheel circumference in inches
• Cadence in RPM
• 60 minutes per hour
• 63360 inches per mile

Frequently Asked Questions

What is the ideal gear ratio for my riding?

The ideal gear ratio depends on your riding style, terrain, and fitness level. Generally:

• Flat roads: 2.6:1 to 3.2:1
• Hills: 1.7:1 to 2.5:1
• Mountains: 1:1 to 1.6:1

How do I calculate gear inches?

Gear inches = (Chainring teeth × Wheel diameter) ÷ Cog teeth This helps compare different gear combinations across different wheel sizes.

What affects my choice of gearing?

• Riding terrain
• Fitness level
• Riding style
• Event type
• Personal preference
• Bike type

How do I optimize my cadence?

• Start with 80-90 RPM as a baseline
• Practice spinning smoothly
• Gradually increase cadence
• Listen to your body
• Adjust based on terrain and conditions

Tips for Gear Selection

1. Match Terrain

   • Use easier gears for climbing
   • Higher gears for descents
   • Middle range for flat sections

2. Consider Fitness

   • Start with easier gears
   • Progress to harder gears
   • Maintain comfortable cadence

3. Event Specific

   • Racing: closer ratio gears
   • Touring: wider range
   • Commuting: practical middle range