Quick Answer: Gear ratio = chainring teeth ÷ cog teeth. 50/17 = 2.94 ratio. Higher ratio = harder/faster
This free bike gear calculator works like classic tools such as Gears4U and Sheldon Brown's gear charts: pick your chainrings, cassette, and tire size, and it calculates gear ratios, gear inches, meters of development, and speed at any cadence for every gear combination. Use it to compare cassettes, find your climbing gear, or check for overlap before you buy a new drivetrain.
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Complete Guide to Bike Gearing
Understanding Gear Ratios
Your bike's gear ratio determines how far you travel with each pedal revolution. It's calculated by dividing the number of teeth on your chainring by the number of teeth on your cassette cog. A higher ratio means you'll go faster but need more power, while a lower ratio makes pedaling easier but reduces speed.
Quick Formula
Gear Ratio = Chainring Teeth ÷ Cassette Teeth
Speed (mph) = Gear Ratio × Wheel Circumference × Cadence × 0.00595
Choosing the Right Gearing for Your Riding
Road Cycling Gearing
Modern road bikes typically use either compact (50/34), semi-compact (52/36), or standard (53/39) chainrings. The choice depends on your fitness level and terrain:
- Compact (50/34): Best for recreational riders and hilly terrain. Provides excellent climbing gears.
- Semi-Compact (52/36): Balanced option for fit riders who want both climbing ability and top-end speed.
- Standard (53/39): For racers and strong riders on flatter terrain.
Gravel and Adventure Gearing
Gravel bikes need wider gear ranges for varied terrain. Popular options include:
- 2x Systems: 46/30 or 48/31 with 11-34 or 11-36 cassette
- 1x Systems: 40-44T chainring with 10-42 or 10-50 cassette
- Gear Range: Aim for 400-500% total range for versatility
Common Gearing Mistakes to Avoid
- Too high gearing: Many riders choose gears that are too hard, leading to knee problems and poor climbing.
- Ignoring cadence: Optimal cadence is 80-100 rpm. Gearing should support this.
- Cross-chaining: Avoid big-big and small-small combinations which wear components.
- Not considering terrain: Match your gearing to where you actually ride, not theoretical needs.
1x vs 2x vs 3x Drivetrains
| System | Range | Weight | Simplicity | Best For |
|---|---|---|---|---|
| 1x (Single) | 400-520% | Lightest | Simplest | Gravel, MTB, CX |
| 2x (Double) | 400-550% | Medium | Moderate | Road, Gravel |
| 3x (Triple) | 550-630% | Heaviest | Complex | Touring, Casual |
How to Calculate Your Ideal Climbing Gear
To determine your ideal climbing gear, consider these factors:
Climbing Gear Formula
- 1. Determine your sustainable climbing power (typically 70-80% FTP)
- 2. Calculate speed on target gradient using: Speed = Power / (Weight × Grade × 2.7)
- 3. Find gear ratio needed: Ratio = Speed / (Cadence × Wheel Circumference × 0.00595)
- 4. Choose cassette/chainring combination that provides this ratio or lower
Gear Inches and Development
Gear inches and meters development are alternative ways to express gearing:
- Gear Inches: (Chainring ÷ Cassette) × Wheel Diameter in inches
- Meters Development: Distance traveled per pedal revolution in meters
Typical Ranges
- • Touring low gear: 20-25 gear inches
- • Road climbing: 30-40 gear inches
- • Flat cruising: 70-90 gear inches
- • Sprint/descent: 100-125 gear inches
Frequently Asked Questions
What is a good gear ratio for climbing?
A good climbing gear ratio is 1.0 or lower. For steep climbs, aim for 0.8-0.9 (like 34/34 or 32/36). Professional climbers often use 36/32 (1.13) as their lowest gear.
How do I calculate bike gear ratios?
Gear ratio = number of teeth on chainring ÷ number of teeth on cassette cog. For example, 50/11 = 4.55 gear ratio. Higher ratios mean harder gears for speed, lower ratios mean easier gears for climbing.
What gear inches do I need for touring?
For touring, aim for 20-25 gear inches as your lowest gear (for loaded climbing) and 100-110 gear inches as your highest (for descents). This typically requires a wide-range cassette like 11-42 or 11-46.
What's the difference between 11-28 and 11-32 cassette?
An 11-32 cassette provides a 14% easier climbing gear than 11-28. With a 50/34 crankset, the 34/32 combination gives a 1.06 ratio vs 1.21 with 34/28, making steep climbs significantly more manageable.
How fast is 90 rpm in each gear?
At 90 rpm with 700x25c tires: 50/11 = 38.5 mph, 50/15 = 28.2 mph, 34/28 = 10.3 mph. Use our calculator above to find exact speeds for your specific gearing and tire size.
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Shimano 105 CS-R7000 11-Speed Cassette
The most common 11-speed cassette upgrade — available in 11-28T (tighter ratios for flats) and 11-32T (wider range for climbs). Pair with the recommended chain whip + lockring tool below to swap at home in 10 minutes.
Tweaking Your Gearing? Top Picks for Each Upgrade
If this calculator told you your low gear is too tall (or your top end is too short), here's what most cyclists actually swap. As an Amazon Associate, we earn from qualifying purchases.
- Wolf Tooth Oval Chainring (110 BCD) Smaller chainring for compact cranks when you need lower gears without changing the cassette. ~$90.
- Park Tool CC-3.2 Chain Wear Indicator Check chain stretch before swapping cassettes — a worn chain destroys a new cassette in weeks. ~$11.
- Park Tool SR-18.2 Chain Whip (Backcountry) The chain whip you actually need to swap a cassette at home. Pair with a lockring tool. Check on Amazon if Backcountry is out of stock. ~$45 for the pair.