Speed at Cadence Calculator
Calculate your ground speed for any gear and cadence combination. Find your ideal cadence for target speeds or see what gears you need.
Results
Visualization
How It Works
The Speed at Cadence Calculator determines how fast you're traveling on your bike based on your gear combination (chainring and cog teeth) and pedaling cadence (rpm). This is essential for understanding your actual ground speed, training at specific intensities, and selecting appropriate gears for different riding conditions.
The Formula
Variables
- Chainring Teeth — The number of teeth on your front chainring (the large ring at the crankset). Typical road bikes have 39-53 teeth; mountain bikes often have 28-38 teeth.
- Rear Cog Teeth — The number of teeth on the specific rear sprocket you're using. Larger numbers mean easier pedaling but lower speeds; smaller numbers mean harder pedaling but higher speeds.
- Cadence — Your pedaling speed measured in revolutions per minute (rpm). Most cyclists maintain 80-100 rpm at steady pace, though this varies by fitness level and terrain.
- Wheel Circumference — The total distance your wheel travels in one complete rotation, measured in millimeters. For a 700c road bike, this is typically 2,080-2,130 mm depending on tire width; mountain bikes are usually 2,050-2,300 mm.
- Speed — Your resulting ground speed in kilometers per hour (km/h), showing how fast you're actually moving forward regardless of terrain.
Worked Example
Let's say you're on a road bike with a 50-tooth chainring, using a 12-tooth rear cog, pedaling at 95 rpm, and your wheel circumference is 2,100 mm. First, calculate your gear ratio: 50 ÷ 12 = 4.17. Next, multiply by cadence: 4.17 × 95 = 395.15. Then multiply by wheel circumference: 395.15 × 2,100 = 829,815. Finally, convert to km/h by multiplying by 60 and dividing by 1,000,000: 829,815 × 60 ÷ 1,000,000 = 49.8 km/h. At this gear and cadence combination, you're traveling at approximately 50 km/h.
Practical Tips
- Find your wheel circumference by measuring the actual tire width you use—a wider tire increases circumference by 5-10 mm compared to narrower tires on the same rim, affecting your calculated speed noticeably.
- Most cyclists naturally settle into their most efficient cadence (usually 85-100 rpm for road cycling), but you can use this calculator to find gear combinations that let you maintain your ideal cadence across different terrains.
- Use this calculator before long rides to understand what speed each gear will give you at your typical cadence, helping you choose realistic targets for interval training or tempo work.
- If your calculated speed seems too high compared to your bike computer, recalculate your wheel circumference—this is the most common source of error, as tire pressure and width both affect the measurement.
- Compare multiple gear combinations at your race-day cadence to identify which gears let you sustain your target speed without excessive muscular fatigue, especially important for long climbs or sustained efforts.
Frequently Asked Questions
What's the difference between cadence and speed, and why does the calculator need both?
Cadence is how fast you're pedaling (rpm), while speed is how fast you're moving forward (km/h). The same cadence in different gears produces completely different speeds—spinning 90 rpm in a small gear might give 20 km/h, but 90 rpm in a large gear could give 45 km/h. The calculator needs both because they work together through your gear ratio to determine actual ground speed.
How do I measure my wheel circumference accurately?
Mark a point on your tire with chalk, roll the wheel forward until that mark touches the ground again, and measure the distance traveled. Alternatively, measure your tire diameter and multiply by 3.14159, though a direct measurement is more accurate since tire pressure and width affect the actual circumference. Most tire manufacturers provide recommended circumference ranges on their product specs.
Why does my bike computer show a different speed than this calculator predicts?
Bike computers measure actual motion using GPS or wheel sensors, while this calculator is theoretical—it doesn't account for wind resistance, terrain changes, or rolling inefficiencies. Also, if your bike computer's wheel circumference setting is wrong, both devices will be inaccurate. Recalibrate your computer's wheel size against a known distance (like a measured mile) to ensure accuracy.
What cadence should I aim for when cycling?
Most recreational cyclists ride comfortably at 80-100 rpm, while professional cyclists often prefer 90-110 rpm for road cycling and slightly lower for mountain biking. The 'best' cadence depends on your fitness level, terrain, and muscular versus aerobic strength—experimenting with this calculator can help you find gear combinations that let you maintain your naturally efficient cadence.
Can I use this calculator to find what gears I need for a specific target speed?
Yes—work backwards by dividing your target speed by your typical cadence, then look for chainring and cog combinations that produce the resulting gear ratio. For example, if you want 40 km/h at 90 rpm with a 2,100 mm wheel, you need a gear ratio of approximately 3.17, which could be achieved with a 50-tooth chainring and 16-tooth cog (50÷16=3.125).
Sources
- Bicycle Wheel Size and Circumference Reference - Sheldon Brown's Bicycle Tech Encyclopedia
- Cadence and Cycling Performance - TrainingPeaks Science of Cycling
- Gear Ratios and Speed Calculation - CyclingTips Bike Setup Guide