If you’re struggling to get up hills or “spinning out” on every descent, the chances are you could do with changing your bike gear ratios!
You should be able to comfortably turn the pedals up any gradient (within reason – 30% is always going to be a challenge, regardless of gearing), and you should be able to pedal through most descents.
Whether you’re riding smooth tarmac, gnarly trails, or grinding some gravel, getting the right gear ratios is vital to enjoying the climbs and descents of a ride.
But what actually are gear ratios? And how should you choose them?
Don’t worry! In this guide, we’ll tell you everything you need to know about bike gear ratios, and you’ll be flying up your local climb in no time. To get you up to speed, we’ll be covering:
- What Are Bike Gear Ratios?
- Bike Gear Ratio Calculator Charts
- How To Optimize Your Bicycle Gear Ratios
Ready to kick into gear?
Let’s get going!
What Are Bike Gear Ratios?
If you’re just getting into cycling, understanding bike gear ratios can be daunting.
The first time you hear someone talking about them, it can sound as if they’re speaking in code. Don’t stress – although it seems unnecessarily complicated, it’s actually remarkably simple.
The numbers you hear thrown around refer to the number of teeth on a chainring or a cassette‘s sprocket. The rule here is that for easier gears in a chainset, you need a lower number of teeth (a smaller sprocket). For easier gears in the cassette, you need a higher number of teeth (a bigger sprocket).
You’ll sometimes hear these two numbers quoted together to describe a particular gear. The order this is usually quoted in is front/back. So a gear of 39/28 would refer to a chainring of 39 teeth, and a cassette sprocket of 28.
The ratio between these two numbers for a particular gear is the gear ratio: this refers to the number of turns the wheel does for every turn of the pedals.
So, in our example of 39/28, the gear ratio is roughly 1.4 (39 divided by 28), meaning that every time you turn the pedals one full revolution, the wheel turns 1.4 times.
You can also use bike gear ratios to calculate speed.
For example, a 700c wheel (the road bike standard) moves 2.31 meters for every revolution. So, one revolution of the pedals at a gear ratio of 39/28 will take you 3.23 meters (2.31 x 1.4). If you multiply this figure by your cadence – let’s say 100 rpm in this case – you can calculate the speed.
In this example, the bike would be traveling at 19.4 km/h (3.23 m x 100 rpm x 60 minutes).
Note that other factors affecting speed, such as weight, air resistance, and rolling resistance, only have the effect of making it more difficult to turn the pedals. They won’t affect the distance the bike moves per pedal revolution.
Bike Gear Ratio Calculator Charts
A “standard” chainset for a road bike is typically 53/39, and a standard cassette might be 11/28. This means that your hardest gear is 53/11 (gear ratio of 4.8), and your easiest is 39/28 (gear ratio of 1.4).
A “compact” chainset will often be 50/34, giving you a hardest gear of 50/11 (gear ratio of 4.55) and easiest of 34/28 (gear ratio of 1.21) when paired with the same 11/28 cassette.
Mountain bikes will typically offer easier gear ratios than road bikes, to allow for the sharp elevation changes and loose terrain encountered when cycling off-road. They’ll often include gearing options with a 1:1 ratio or less, which is far less common on road bikes.
1x drivetrains are also increasingly popular for mountain and gravel biking for their simplicity and easy maintenance. These have only one chainring at the front, and compensate for the reduction in the number of gears with wide-ranging cassettes.
Mountain Bike 1x Chainset (40t)
Mountain Bike 1x Chainset (32t)
Remember, if you want to calculate the ratio for a gearing combination that’s not included in these charts, simply divide the number of teeth on the chainring by the number of teeth on the cassette sprocket.
How To Optimize Your Bicycle Gear Ratios
Bike Gear Ratios For Road Cycling
Until recently, it was considered “easy” gearing to have an 11-28 cassette at the back, and anything other than a standard chainset on a road bike was unusual. A typical bike racer’s cassette might only offer 21 or 23 teeth as their largest sprocket.
Times have changed, however, and many cyclists ride compact chainsets with cassettes offering sprockets all the way up to 32 teeth. This is largely due to the increase in the number of speeds (the number of gears on the cassette) available with modern groupsets.
Cyclists with high-end groupsets can now access as many as 12 speeds, allowing them to extend the range of the cassette without increasing the jumps between sprockets.
For example, an 11-28 with a 9-speed cassette would likely have the combination 11-13-15-17-19-21-23-25-28. A modern 12-speed cassette, however, might offer an 11-13-15-17-19-21-23-25-27-29-31-34 combination, which doesn’t compromise at all on the spacing, but significantly extends the range of gearing.
Some pro cyclists still ride with a standard chainset (or bigger) and a 10-23 cassette, especially for flat stages or time trials.
But remember, they’re pros for a reason. Just because you see Pogačar riding a brutal gearing combination doesn’t mean you have to!
It’s much more sensible to choose a gearing that suits your abilities, and will actually allow you to comfortably get up your local brutal climbs, without the need to be grinding away at the pedals.
The first step towards optimizing your road bike gearing is asking yourself what type of roads you most enjoy riding on (and ride on the most).
For example, if you live in the Rockies, the Alps, or the Lake District, you should choose gearing that is well-suited to climbing. In this case, something like a compact (or sub-compact) with an 11-34 cassette might be sensible, depending on how strong a cyclist you are.
If you’re more of a flat-ground champion, and the sight of a slight incline makes you sweat behind the knees, it’s not a terrible idea to stick with some higher gearing.
A standard or compact chainset with an 11-28 cassette should be manageable for most riders provided they steer clear of the mountains, and the smaller gaps between gears should afford you smoother shifting and a greater ability to fine-tune your gear choice.
Bike Gear Ratios For Gravel
The first decision when it comes to gravel bikes is whether to go with a 2x or 1x chainset. The answer to this question is, again, decided by the places you like to ride your bike – and personal preference.
If you spend a fair amount of time on the road, then a 2x makes more sense, since your speed will be more consistent than if you’re off-road, and the finely-tuned gearing will come in handy.
If you spend most of your time off-road, the varying terrain will mean that your speed varies much more, so a 1x chainset will work just fine.
If you’re going to go for a 2x, then you should go for a compact or sub-compact. The wider tires and more relaxed geometry of a gravel bike will be harder to push, especially if it’s loaded with bags, so low gear ratios are ideal.
If you’re going for a 1x, then a 40t chainring will probably be best for the style of riding a gravel bike is capable of.
As for cassettes, the minimum you’re going to want at the back is an 11-34. Getting up a steep hill off-road is significantly harder, and it can feel like the uneven terrain just saps the energy out of you.
This is why it’s sensible to try and have a gear ratio as low as possible. 11-42 is the maximum cassette range offered with Shimano GRX, for example, and could be advisable if you plan on touring on the bike.
Gear Ratios For Mountain Bikes
Likewise, choosing gear ratios for mountain biking comes down to what type of mountain biking you’re into.
Mountain bikes these days often come with a 1x chainset, and for good reason. Not only are they simpler, lighter, and feature less cabling to snag on a branch, but they also free up the left shifter to activate a dropper post!
If you’re going to be doing mostly XC mountain biking, but over gentle hills and more consistent trail surfaces, then a 40T chainring at the front could be a good choice. This can be paired with a 10-51 cassette for a huge gear range able to tackle the majority of trails.
If you’re more of a rugged rider, and you prefer rougher, unkempt trails or even off-piste XC mountain biking, or perhaps you just love crazy steep hills, then a 32t chainring would make sense for you.
Now You Know All About Bike Gear Ratios…
You can absolutely nail your gearing, no matter the type of riding you’re into!
Don’t let your gearing hold you back any longer. Lower gear ratios will allow you to get up that climb you’ve had to push up for months, and give you more confidence to go out and tackle any ride you fancy!