Last updated: January 6th, 2023
Single-speed bikes are easy to maintain and liberating to ride.
But when you only get one gear, it’s got to be the right one!
Here’s what you need to know about single-speed gear ratios, so you can tackle more terrain with less pain.
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What’s the best gear ratio for a single-speed bike?
It’s highly personal, but I advise single-speed bike riders to start with a gear ratio of:
- 1.8:1–2:1 on mountain bikes
- 2.2:1–2.4:1 on city & cruiser bikes
- 2.5:1–2.7:1 on road & hybrid hybrid bikes (with a freewheel)
- 2.7:1–2.8:1 on fixed-gear road bikes
No one gear is universally the best. Rather, the optimal gear ratio ultimately depends on your bike, fitness, terrain, and riding style. It will also change over time.
Stick with it for several rides, then adjust 1-2 teeth at a time until you’ve hit the right balance between speed vs. climbing ability. Keep unused spares on hand so you can test new ratios quickly and cheaply in the future.
Many mountain bikers go lower, and many road bikers go higher (especially on fixies). You may also want to go 1-2 teeth lower for frequent stoplights, since it’s always tough to start without momentum.
Again, these are just starting points that should be not bad for most people in most situations.
When you’re comparing different bikes, it’s helpful to use gear inches, not gear ratios. It’s a simple and wonderfully useful number, so more on that later.
Caveat: “perfect” gearing doesn’t exist
The best gear ratio isn’t perfect; it’s just a good balance of trade-offs. After all, it’s physically impossible for one speed to feel fast (high RPM) and easy (high torque) at the same time. Otherwise, multi-speed drivetrains wouldn’t exist!
In other words, it’s about realistic expectations. No magical gear ratio lets you climb a mountain and bomb back down with ease. One of the two—and usually both to an extent—is going to suffer.
If you find that too frustrating, then single-speeds probably aren’t for you. And that’s perfectly reasonable!
What exactly is a bicycle gear ratio, anyway?
It refers to the ratio of front teeth to rear teeth. For instance, if you have a 44-tooth chainring and a 22-tooth cassette/cog/freewheel, then the ratio is 44:22, which simplifies to 2:1.
That tells you how many times the rear wheel turns for every pedal revolution. For example, the rear wheel goes around twice per pedal stroke with a 2:1 ratio, three times per pedal stroke with a 3:1, and so forth.
This has two important implications:
- The higher the ratio, the more work you’re doing with each pedal stroke, and the less torque you produce. That’s why it feels faster but tougher when you use a larger front gear and/or a smaller rear gear.
- Any gear combination with the same ratio will feel the same to ride. For instance, 44:22, 32:16, and 52:26 all equal 2:1, so they’re functionally identical. That’s why we just say “2:1” instead of the exact number of teeth.
(Geeky technical caveat: they’re not exactly the same. Smaller gears make the chain curve more sharply, which creates ever so slightly more mechanical resistance. In a laboratory setting, 34:17 might actually be harder work than 40:20. In reality, the difference is imperceptible.)
Single speed gear ratio table
Gear ratio calculation is easy, but it’s always nice to have a quick reference. To that end, this table provides every gear ratio within common ranges for single-speed bikes.
What’s the best way to change your gear ratio?
Make small changes, usually no more than 3-4 teeth in the front or 1-2 teeth in the rear. Change only the front or the rear, not both at once, so the change isn’t too drastic.
It gets expensive to swap gears repeatedly. Consider buying lightly used gears for testing purposes, then replace them with new ones (in the same size) once you’ve found the right ratio.
(You won’t want to use the secondhand ones long-term, since they’re often a bit worn or rounded out. This may accelerate chain wear and increase resistance.)
Now, how do you decide which gears to change? Here’s how I approach it:
- Chainring adjustments are easier to fine-tune, since you can change just one tooth out of 30- to 50-something up front, versus one out of 10- to 20- something in the back.
- Chainrings are usually cheaper and easier to replace than rear sprockets.
- It’s easier to chain links than to add them, so move to smaller gears rather than larger, when possible. That means decreasing the front for a lower gear ratio, or decreasing the rear for a higher gear ratio.
Some riders prefer a “dingle-speed” set-up wherein the freewheel and chainring each have two close gears. This allows a manual change between a high and low gear. It’s irritating to change often, but not bad for 1–2 changes from pavement to trails or from flats to huge climbs. You’ll need angled drop-outs (not horizontal track ends) or a chain tensioner in order to accommodate the slight differences in gear circumference.
Caveat: watch for frame limitations
Some frames can only accommodate chainrings up to a certain size. Fortunately, as discussed, you can pair that with whatever rear cog creates the ratio you want.
Let’s say you have a 20-tooth cog and you want a 2.5:1 ratio. That indicates a 50-tooth chainring.
But what if your frame’s chainstays can only clear 46 teeth?
Simple: use a 45-tooth chainring, and go with an 18-tooth rear cog. The ratio is still 2.5:1, but now you’re clear of the frame.
Better still, go with an even smaller 2:1 combination, like 40:16. That leaves a few teeth’s worth of clearance, just in case you want to fine-tune the ratio with a slightly larger chainring in the future.
A better way to compare single-speed gearing
Gear ratios are a fine way to keep track of what works for your bike right now. But they have one shortcoming: they don’t account for wheel size, so they aren’t comparable between bikes.
Instead, you can use gear inches to compare different bikes (or the same bike before/after a tire change). To calculate gear inches, find:
Front teeth x rear teeth / rear tire diameter in inches
The metric equivalent is meters of development, or:
Front teeth x rear teeth / rear tire circumference in meters
(Rear tire diameter/circumference is always measured to the tire tread.)
The math is simple, but rim and tire sizing isn’t always obvious. I like to use this calculator to easily account for them.
How wheel & tire size affect your gear ratio
Larger wheels or fatter tires both mean larger circumference, so each revolution covers more distance (and requires more effort). The opposite applies to smaller wheels or skinner tires.
To give a dramatic example, if you switched to a bike whose wheels are half the size, then the same gear ratio would require half as much effort, and turn the wheel half as many times per pedal stroke.
Consequently, you’d calculate half the gear inches, too.
What about crank length?
If you want to be as precise as possible, then you also need to account for crank length. It varies between bikes, but does affect mechanical advantage (ease/difficulty) of a gear.
The standard way to do this is with a measurement called gain ratio, which is:
(Wheel radius / crank length in the same unit) x (front teeth / rear teeth)
Do you actually need to worry about this? In my experience, not really. Gear inches is sufficient for most cyclists to find the right gear ratio.
Crank length absolutely does affect your gear choices. And if you’re changing your cranks, then you’ll want to change your gears to maintain your preferred gain ratio.
But any two bikes will also have several other differences in feel. In light of all those factors, I personally have never found it worth comparing crank length.
A note on gearing for fixed-gear bikes
Generally, riding a fixie calls for a slightly higher gear ratio than you’d use with a freewheel. Coasting isn’t possible, so you need to be wary of “spinning out” while descending on a fixed-gear.
You might think this would make climbing harder, but that’s not quite the case. The flywheel effect of the rear wheel helps maintain your momentum, so fixed-gear cyclists often report climbing faster despite the higher gear ratio.
Conclusion: the right single-speed gear ratio for you
No gear ratio is perfect. With just one gear, you’ll always struggle to some degree on climbs, descents, or likely both.
However, 2:1 is a good starting point for MTB, and 2.5:1 is good for road. From there, plan on swapping gears a few times (never more than 1-2 teeth each time) until it feels like the right compromise between speed and climbing ability.
Gear ratio is a useful number, but it’s more helpful to use gear inches, which accounts for wheel and tire size. Those vary widely, so the same gear ratio may feel wildly different on any two bikes. Conversely, a different gear ratio may yield the same gear inches and therefore (roughly) the same feel.
So, to convert the initial gear ratios above, we’d get roughly 55″ for MTB, 67″ for road, and 73″ for fixed-gear bikes. Again, these shouldn’t be too bad, but you’ll almost certainly want to adjust from there!