Mountain Bike Gear Calculator
Optimized for modern 1x11 and 1x12 drivetrains. Find out if your 'granny gear' is low enough for the steepest climbs.
Drivetrain Specs
Common 1x sizes: 30, 32, 34.
SRAM Eagle: 50/52. Shimano: 51.
*A ratio below 0.65 allows for spinning up >15% grades.
Understanding MTB Gearing: The 1x Revolution
Mountain biking has undergone a massive shift from 3x9 drivetrains to simplified 1x11 and 1x12 systems (like SRAM Eagle and Shimano Hyperglide+). By removing the front derailleur, bikes are lighter and simpler, but gear selection becomes critical.
The Magic Number: 0.64
For general trail riding and steep technical climbs, most riders aim for a lowest gear ratio around 0.64.
Example: 32t Chainring ÷ 50t Cog = 0.64
Wheel Size Matters (29er vs 27.5)
This is where Gear Inches become vital. A 29-inch wheel has a larger circumference than a 27.5-inch wheel. This means a 29er is effectively "geared higher" (harder to pedal) than a 27.5 bike with the exact same chainring and cassette.
- On a 27.5" bike: A 32t chainring is standard.
- On a 29" bike: Many riders drop to a 30t chainring to regain the easy climbing feel, or rely on huge 52t cassettes.
Common MTB Setups
| Style | Chainring | Cassette | Ratio | Verdict |
|---|---|---|---|---|
| XC Race | 34t / 36t | 10-51t | 0.67 | Fast, harder climbing |
| Trail / Enduro | 32t | 10-52t | 0.61 | Balanced |
| Adventure / Bikepacking | 30t | 11-50t | 0.60 | Maximum climbing ease |
Related Tools
If you are building a new bike, don't forget to check your Chain Length, especially for high-pivot full suspension bikes where chain growth is significant.