1Road bike 50/17 at 90 RPM
Inputs
Chainring50T
Cog17T
Wheel700c
Tire25mm
Result
Gear Inches78.5
50/17 = 2.94 ratio × 26.7" wheel = 78.5 gear inches.
Be the first to rate this calculator
No ratings yet
Cycling Gear Inch Calculator
Gear Inches
77.8
Gain Ratio
5.81
Speed
20.8 mph
Gear Inches
77.8
2.94 gear ratio
Gain Ratio
5.81
Development
6.2 m
Speed at 90 RPM
Speed (mph)20.8 mph
Speed (km/h)33.5 km/h
Wheel Diameter26.5″
What You'll Need
CYCPLUS Wireless GPS Bike Computer G1, 70g, 2.0" Screen, IPX6, 1200mAh
$32.99
View on Amazon
iGPSPORT BSC500 GPS Bike Computer, 3.3'' Touchscreen MAP & Voice Navigation Ebike Mode Climb Training Function
$149.99
View on Amazon
CATEYE Urban Wireless Bike Computer
$34.95
View on AmazonAs an Amazon Associate, we earn from qualifying purchases.
Price as of Jul 24, 2026. Product prices and availability are accurate as of the date indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
Related calculators
Bike Fit CalculatorFrame sizing and saddle heightBike Gear Ratio CalculatorGear ratio for all setupsMTB Tire Pressure CalculatorOptimal tire pressure for MTBBMI CalculatorCheck your BMI and see which weight category you fall into based on WHO standards. View health ranges, get personal recommendations, and track your metrics.Macro Split CalculatorChoose a protein, carb, and fat ratio then convert percentages to daily grams. Compare popular splits like 30/40/30 or 40/35/25 for your calorie target.Heart Rate Recovery CalculatorCalculate your heart rate recovery score after exercise to assess cardiovascular fitness. Compare HRR results by age, gender, and fitness level instantly.
Example Calculations
2MTB climbing gear 30/50
Inputs
Chainring30T
Cog50T
Wheel29"
Tire2.3"
Result
Gear Inches19.3
30/50 = 0.60 ratio × 32.2" wheel = 19.3 gear inches.
Frequently Asked Questions
QWhat are gear inches in cycling?
Gear inches represent the effective wheel diameter multiplied by the gear ratio. A 50T chainring with a 17T cog on a 700c wheel gives about 79 gear inches, meaning each pedal revolution moves you as far as a 79-inch wheel rolling once.
- Higher gear inches = harder gear, more speed
- Lower gear inches = easier spinning, better climbing
- Road bikes: typically 20–115 gear inches
- MTB: typically 15–90 gear inches
| Gear Range | Gear Inches | Use Case |
|---|---|---|
| Easy climbing | 20–40 | Steep hills, loaded touring |
| General riding | 50–75 | Flat to rolling terrain |
| Fast cruising | 80–110+ | Flat roads, sprinting |
QWhat is gain ratio and why does it matter?
Gain ratio measures the distance traveled per unit of pedal arc distance. Unlike gear inches, it accounts for crank length, giving a more accurate comparison across different bikes.
- Gain ratio of 3.0 = each meter of pedal travel moves you 3 meters
- More useful than gear inches for cross-bike comparison
- Developed by Sheldon Brown
- Typical range: 1.5 (easy) to 8.0 (hard)
QHow do I calculate speed from gear ratio?
Speed equals the development distance (wheel circumference times gear ratio) multiplied by cadence. At 90 RPM with a 50/17 on 700x25c, you travel about 21.5 mph.
- Development = wheel circumference × gear ratio
- Speed (km/h) = development(m) × cadence × 60 / 1000
- A 90 RPM cadence is typical for trained cyclists
- Each tooth change shifts speed by ~1–2 mph at same cadence
QWhat gear ratio should I use for climbing?
For climbing, target gear inches under 40 (roughly a 1:1 ratio or lower). A 34T chainring with a 34T cassette cog gives about 27 gear inches on a road bike, good for steep 10%+ grades.
- 10%+ grade: gear inches under 30
- 5–10% grade: gear inches 30–50
- Rolling hills: gear inches 50–70
- Flat time trial: gear inches 90–115
Related Resources
More Health Calculators
Fitness, nutrition, and cycling tools
Last Updated: Jul 24, 2026
This calculator is provided for informational and educational purposes only. Results are estimates and should not be considered professional financial, medical, legal, or other advice. Always consult a qualified professional before making important decisions. UseCalcPro is not responsible for any actions taken based on calculator results.