What Is Gear Ratio and Gear Inches on A Fixie? (Explained)

You already know that a fixed-gear bike has only one gear. Well, it may seem like a dumb question, but if a fixed gear (or single speed) bike has just one gear, then which gear is it exactly? And what are the gear ratio and gear inches in the first place?

A bike’s gear ratio is the number of teeth on the front sprocket relative to the back sprocket. The number of teeth on the front sprocket determines how fast the bike will go, and the number of teeth on the rear sprocket determines how slow the bike will go. A high gear ratio will make the bike go faster, and a low gear ratio will make it go slower. Most fixed-gear bikes come standard with a chainring and sprocket of 46 teeth and 16 teeth, respectively, providing a gear ratio of 46:16. 

But there’s a lot more to it than that. So, in this article, you will learn what a gear ratio is, what gear inches are, and how to calculate the perfect gearing for you and your bike. But before we dive too deep into bicycle terminology and its specifics, we need to understand what a gear ratio is.

Editor’s note: This article was updated on June 13, 2022, to include additional information regarding bicycle gearing.

Before getting to know about gear ratios, let’s first understand their functions in the first place.

What is gear ratio on a bicycle?

A bike’s gear ratio is the number of teeth on the front sprocket relative to the back sprocket. It also indicates how ‘easy’ or ‘hard’ its gearing configuration is. High gear ratios require more pedal power. Conversely, lower ratios are easier to ride.

You don’t need to calculate the gear’s circumference or anything like that. Just look at the sprockets.

The gear ratio is calculated by dividing two whole integers by the fractional part: the number of teeth on the chainring (the front cog) divided by the number of teeth on the sprocket (the rear gear) (the rear cog).

The gear ratio of a bike with a 46-tooth chainring and a 16-tooth sprocket is commonly denoted with a colon; 46:16.

Gear ratio in decimal form

The gear ratio of 46:16, for example, may be represented as 2.875 when expressed as a decimal. (You’ll get 2.875 if you divide 46 by 16 on your calculator). This implies that, with this 46:16 gear ratio, the rear wheel does over three (2.875) complete spins with each revolution or rotation of the cranks.

What are gear inches?

Using gear inches is a more accurate way to gauge a bicycle’s mechanical advantage. This measurement takes the diameter of the rear wheel (as well as the width of the tire) into consideration. 

However, since the 700c rim diameter is common on almost all adult bicycles, and tire width is a very insignificant increase, we may disregard this element and discuss gear ratios exclusively.

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Gear ratio on fixed gear bikes vs. geared bikes

Now that we’ve learned how to speak about gear ratios, let’s look at an example. 

Imagine we have a multi-speed road bike with 42 and 52 tooth chainrings and a cassette with 11–28 tooth sprockets. The sprocket in the fourth slot of this cassette typically has 18 teeth. So the ratio would be 52:18, or 2.88, if you rode this bike “in fourth gear” with the chain over the large ring.

This is a near approximation of our most frequent fixed gearing ratio, which is 46:16. Written as a decimal, that’s 2.875.

So, to get a feel of what it’s like to ride a 46:16 single-speed bike, you could just change your road bike onto the bigger chainring and fourth sprocket. That is, assuming your gearing configuration follows our example above.

But what if your gearing arrangement differs? In the following part, we’ll discover how to figure out what gear on your multi-speed bike best fits the gear ratio of any single-speed bike you would consider purchasing. On a similar note, the torque provides a frictional force that propels the bike forward.

How to choose the right gearing

Now we’re going deep into the weeds of gear ratios. Fortunately, the chart below makes it straightforward to discover equal gear ratios. This way, you don’t even need to make any calculations.

The top numbers indicate how many teeth the chain ring has, while the bottom numbers in the leftmost column indicate how many teeth the sprocket has. Dividing the former by the latter gets you the decimal value in the table.

Teeth	40	42	44	46	48	50	52	54
11	3.6	3.8	4.0	4.2	4.4	4.5	4.7	4.9
12	3.3	3.5	3.7	3.8	4.0	4.2	4.3	4.5
13	3.1	3.2	3.4	3.5	3.7	3.8	4.0	4.2
14	2.9	3.0	3.1	3.3	3.4	3.6	3.7	3.9
16	2.5	2.6	2.8	2.9	3.0	3.1	3.3	3.4
18	2.2	2.3	2.4	2.6	2.7	2.8	2.9	3.0
21	1.9	2.0	2.1	2.2	2.3	2.4	2.5	2.6
25	1.6	1.7	1.8	1.8	1.9	2.0	2.1	2.2
28	1.4	1.5	1.6	1.6	1.7	1.8	1.9	1.9

You can see that 52:18 was equal to 46:16. You may check this by looking at the drrata in the table above. For example, note that the numbers have been adjusted to 1 decimal point, so 46/16 = 2.875 becomes 2.9.

Let’s assume you’re seeking to purchase a fixie that comes with a 46:18 gear ratio (meaning a 46-tooth chain and an 18-tooth sprocket). What gear on your multi-speed bike might you attempt to get close to the comparable result?

Well, if you look up 46:18 on the chart, you’ll see 2.6. So if you see 2.6 anywhere else on the chart, you may assume that the gear ratio is the same.

For example, 54:21 has a value of 2.6, implying you might try pairing your 54-tooth chain ring with your 21-tooth sprocket. Values like 2.5 and 2.7 are similar, so anything like 52:21 or 40:16 would be nearly equal.

Are you looking for more advice? Take a look at this video called “What Is The Best Fixed Gear Ratio?” from the Dave Noakes YouTube Channel.

How can I change the gear ratio on my bike?

A fixed-gear bike with an average 46:16 gear ratio could be what you’re looking for. You enjoy riding it, but you just wish the gearing was a bit easier—that way, climbing hills wouldn’t be such a headache.

The most likely course of action is to upgrade from a 16-to-18-tooth sprocket. The gear ratio would drop from 2.9 to 2.6 due to this change. You can verify this information by looking up the relevant values in the table.

The 46-tooth chainring may be replaced with a 44-tooth one to reduce the gear ratio further. This would have a less significant impact, reducing the ratio to 2.8. However, unlike sprockets, chainrings are often more costly and time-consuming to install.

Of course, if the contrary is true and you want a tougher gear ratio—it may be because your local region is relatively flat—then you’d either swap to a smaller sprocket or a bigger chain ring.

If you are looking for a rear-wheel cog with a different ratio, check out the ones below.

Frequently asked questions (FAQ)

Below are some commonly asked questions regarding gearing on a fixie, single-speed, or track bike.

Conclusion

So that’s it, Gear ratio demystified. And the handy chart makes it even easier to understand!

This article covered what gear ratio is, what gear inches are, and how to calculate the perfect gearing for your bike. Here are some key takeaways:

Key takeaways

• Most fixed-gear bikes come standard with a chainring and sprocket of 46 and 16 teeth.
• Gear inches are more accurate than gear ratios, but they’re less often used.
• You can change your gear ratio by swapping your bicycle’s rear cog or chainring.

So, what gear ratio configuration are you using? Let us know in the comments below (we read and reply to every comment). If you found this article helpful, check out our full blog for more tips and tricks on everything fixie. Thanks for reading, and stay fixed.

Helpful resources

• Articles about Fixed Gear and Singlespeed Cycling and Equipment 
• Fixed-gear bicycle – Wikipedia
• How To Ride A Fixed Gear Bike | GCN