How to Use the Calculator
To use the calculator, follow this step. Choose the size of your bike wheel, the size of your tires, input your preferred cadence, and finally input the number of teeth on your chainrings and cassette.
Press the calculate button for your results.
If you’re unsure about what to input, here’s a short guide that might help:
- Rim Size is the diameter of your wheel. You can find this measurement by looking at the side of your tire.
- Tire Size is the width of your tires in millimeters. This number can be found on the side of your tire as well.
- Cadence is how many revolutions your pedals make per minute, or how fast you pedal your bike. You need a cadence sensor to find your natural cadence, but most cyclists pedal at 80-95 RPM
- Chainring is the number of teeth on the front sprockets of your bike by the crank arms. The most common sizes for road bikes are 50, 52, or 53 teeth on the outside and 36 or 34 on the inside. So, for example, if you have 52 and 36 chainrings, enter “52,36” into the calculator
- Cassette is the number of teeth on the back sprockets of your bike. Examples of cassette sizes are 11-28, 11-30, 11-34, and so on. There are usually 10 to 12 sprockets on the cassette, depending on the brand of your groupset. If you can’t remember every number of cogs in your cassette, below is a list of standard cassette sizes for popular brands of groupsets.
Standard Bike Cassette Sizes
For road bike groupsets:
- Shimano 11-speed (11-25t): 11,12,13,14,15,16,17,19,21,23,25
- Shimano 11-speed (11-28t): 11,12,13,14,15,17,19,21,23,25,28
- Shimano 11-speed (11-30t): 11,12,13,14,15,17,19,21,24,27,30
- Shimano 11-speed (11-32t): 11,12,13,14,16,18,20,22,25,28,32
- Shimano 11-speed (11-34t): 11,13,15,17,19,21,23,25,27,30,34
- Shimano 12-speed (11-30t): 11,12,13,14,15,16,17,19,21,24,27,30
- Shimano 12-speed (11-34t): 11,12,13,14,15,17,19,21,24,27,30,34
- SRAM 12-speed (10-28t): 10,11,12,13,14,15,16,17,19,21,24,28
- SRAM 12-speed (10-30t): 10,11,12,13,14,15,17,19,21,24,27,30
- SRAM 12-speed (10-33t): 10,11,12,13,14,15,17,19,21,24,28,33
- SRAM 12-speed (10-36t): 10,11,12,13,15,17,19,21,24,28,32,36
- Campagnolo 12-speed (11-29t): 11,12,13,14,15,16,17,19,21,23,26,29
- Campagnolo 12-speed (11-32t): 11,12,13,14,15,16,17,19,22,25,28,32
- Campagnolo 12-speed (11-34t): 11,12,13,14,15,16,17,19,22,25,29,34
The level of your groupset (105, Ultegra, Dura-Ace, or Rival, Force, Red) doesn’t matter, all you need is the brand name and how many sprockets there are.
Mountain bike groupsets:
- Shimano XTR 11 speed (10-40t): 11,13,15,17,19,21,24,27,31,35,40
- Shimano XTR 12 speed (10-45t): 10,12,14,16,18,21,24,28,32,36,40,45
- Shimano XTR 12 speed (10-51t): 10,12,14,16,18,21,24,28,33,39,45,51
- SRAM Eagle (10-50t): 10,12,14,16,18,21,24,28,32,36,42,50
- SRAM Eagle (10-52t): 10,12,14,16,18,21,24,28,32,36,42,52
These numbers are in a ready-to-use format. Choose your groupset, then just copy and paste the numbers into the calculator. If you have a custom cassette or if yours isn’t on the list above, just input the numbers manually separated by commas.
Why Use This Calculator?
Getting into the right cadence is very important in cycling. If you’re pedaling too slowly, you will get muscular fatigue faster and are at a greater risk of a knee injury. On the other hand, pedaling too quickly will stress your aerobic system and lead to a higher heart rate. Each person has a different preferred cadence, but the ideal cadence for most cyclists is between 80-95 RPM.
Using this calculator, you can find the gearing that will help you maintain your ideal cadence. Just try different sets of cassettes and see if you can get the right speed with your preferred cadence.
You can also use the calculator to find out how fast or slow you can go with your current setup. This is useful when you go uphill and downhill. You don’t want to run out of cassettes going uphill and have to pedal really slowly, which is bad for the knee. Similarly, you don’t want to spin too fast going downhill.
How to Calculate Your Bike Speed
The calculation for speed is actually very simple. You can easily calculate a single given chainring-cassette combination. The formula for speed is:
Speed = Wheel circumference × Gear ratio × RPM
You can get the total wheel circumference by adding the diameter of the rim and the tire height. Assuming bicycle tires are tube-shaped when inflated to the right pressure, tire height should be about the same as its width (times two for diameter).
For example, if the type of your wheel is 700c (622 mm diameter) and the width of your tire is 23 mm, then:
Wheel circumference = (622 + 23 × 2) × pi = 2098.58 mm.
The gear ratio is the number of chainring divided by the cassette. The rest is a matter of unit conversion. To get a result in km/h, multiply the formula by 60 and divide by 1,000,000. To get a result in mph, divide the km/h by 1.609.
Where to Find Your Chainring and Cassette Sizes
Some people don’t know their chainring and cassette sizes, and that’s normal because when you buy a bike for the first time the shop doesn’t usually explain it to you. But, if you want to find out what chainring and cassette you’ve been using all this time, here’s how.
The chainrings are located on the right side of your bike, by the crank arm where your pedal is attached. The size of your chainrings is usually printed on the chainring itself. If you can’t find it on the outer side (right side) of the chainring, look at the inner side (left side) too.
In the image above, the size of my chainrings is 52-36, meaning there are 52 teeth on the big ring and 36 teeth on the small ring. Though some brands might print the numbers individually on each ring rather than as a set because they are separable.
For the cassette sizes, they are usually engraved on the outer side (right side) of each of your rear sprockets. The numbers are small and a bit hard to see, especially if your cassette is old or dirty.
You don’t have to find all of the small numbers, thankfully, at least if you’ve never modified your cassette. You only need the smallest and the biggest sprocket sizes, and how many sprockets there are.
In the image above, my smallest sprocket is 11 teeth – written as 11A on the cassette – and the biggest is 30 teeth. So it is an 11-30t cassette. Since it is an 11-speed Shimano cassette (meaning there are 11 sprockets, not because the smallest gear has 11 teeth, a common mistake), if you refer to the list above the cassette sizes are 11,12,13,14,15,17,19,21,24,27,30.
If you’re not sure about the brand of your cassette and there are no numbers engraved on each sprocket, you will have to count the teeth one by one for each sprocket. A tedious task, I know.