Bike Chain Size Chart | Match Width To Speed

Most bicycles use chain widths tied to cassette speed, with common fits ranging from 1/8-inch single-speed to narrow 12-speed chains.

A bike chain size chart saves a lot of guesswork. One wrong chain can leave you with slow shifting, chain skip, noisy pedaling, or a chain that will not even sit on the cogs the right way. The good news is that chain sizing follows a clean pattern once you know what the numbers mean.

For most riders, the fastest path is this: count the gears on the back, then match the chain to that speed. Single-speed, BMX, track, and many hub-gear bikes use wider chains. Multi-gear derailleur bikes use narrower chains as the cassette gets more crowded. That is the core pattern, but the small details still matter when you are buying parts.

What Bike Chain Size Really Means

Nearly all modern bicycle chains share the same 1/2-inch pitch. That is the distance from one pin to the next. What changes is the width between the inner plates and the total outside width of the chain. As rear cassettes gained more cogs, chains had to get narrower on the outside so they could move cleanly between tighter sprocket spacing.

You will usually see chain size written in one of two ways. One is by speed, such as 8-speed, 10-speed, or 12-speed. The other is by dimensions, such as 1/2 x 3/32-inch or 1/2 x 11/128-inch. Single-speed riders run into the width numbers more often. Road, gravel, hybrid, and mountain riders usually shop by speed first.

There is one extra wrinkle. Brand-specific shapes now matter on some 12-speed systems. A Shimano-style 12-speed chain is not the same as a SRAM Flattop road chain, and SRAM T-Type chains sit in their own lane too. Once you reach newer 12-speed parts, “close enough” is a bad bet.

How Chain Width Tracks With Drivetrain Speed

Older derailleur systems had more room between cogs, so they could use wider chains. Current cassettes pack more gears into nearly the same space, which means the chain must be slimmer. That is why 6-, 7-, and 8-speed chains are much wider than 11- and 12-speed chains.

Single-speed bikes work by a different rule. Since there is no side-to-side shift across a cassette, the chain can be wider and tougher. Many BMX, track, and heavy-duty city bikes use a 1/8-inch chain. Many single-speed road and commuter setups use 3/32-inch. The chainring and rear cog width must match the chain width, or the fit will feel sloppy or not go on at all.

How To Pick The Right Chain In Minutes

Count The Rear Cogs

If your bike has one sprocket in back, you are in single-speed territory and width matters most. If it has a cassette, count the cogs. Eight cogs means an 8-speed chain. Ten cogs means a 10-speed chain. That sounds almost too easy, but that rule gets most replacements right on the first try.

Match Single-Speed Width To The Teeth

A 1/8-inch chain needs 1/8-inch chainrings and cogs. A 3/32-inch chain needs 3/32-inch teeth. A wider chain on narrow teeth may run, but it can feel loose and noisy. A narrow chain on a wide tooth will not seat right. If you ride a fixie, BMX bike, cargo bike, or old city bike, this step matters as much as speed count.

Watch For Brand-Specific 12-Speed Chains

Modern 12-speed setups are where riders get burned. Shimano-style 12-speed chains and cassettes live in one family. SRAM road Flattop chains live in another. SRAM Transmission, often called T-Type, uses its own chain shape as well. If your bike is 12-speed and newer, use the exact chain family named by the drivetrain maker.

When E-Bike Labels Matter

An e-bike chain is not a different size class by itself. It still has to match the speed and chain profile of the drivetrain. What changes is build strength. Mid-drive bikes put more load through the chain, so many brands sell e-bike versions with tougher pins or plates. Buy by speed first, then pick the stronger version if your bike needs it.

Bike Chain Size Chart By Drivetrain Type

Use this chart as the starting point when you are replacing a chain. It lines up the bike style, the chain size you will usually need, and the fit notes that trip people up most often.

Drivetrain	Usual Chain Size	Fit Notes
BMX, track, heavy-duty single-speed	1/2 x 1/8 in.	Built for wide teeth and straight chainlines; too wide for most derailleur systems.
Single-speed road, commuter, many hub-gear bikes	1/2 x 3/32 in.	Works with narrower single-speed cogs and chainrings; common on everyday bikes.
5-speed derailleur	1/2 x 3/32 in.	Older standard; shop in the 6/7/8-speed family unless the maker says otherwise.
6-, 7-, and 8-speed derailleur	1/2 x 3/32 in.	These speeds often share chain fit; outside width is wider than 9-speed and up.
9-speed derailleur	1/2 x 11/128 in.	Narrower outside width, commonly around 6.6 mm by pin length depending on model.
10-speed derailleur	1/2 x 11/128 in.	Still narrow inside, slimmer outside, often near 5.9 mm by pin length.
11-speed derailleur	1/2 x 11/128 in.	Outer width gets tighter again, commonly around 5.5 to 5.65 mm.
12-speed derailleur, Shimano-style	1/2 x 11/128 in.	Very narrow, often around 5.2 to 5.3 mm; do not swap blindly with Flattop chains.
12-speed SRAM Flattop Or SRAM T-Type	Brand-specific 12-speed	Use the exact chain family your drivetrain calls for.

Current repair and maker references line up on the same pattern: 6/7/8-speed chains share one family, then each step up gets narrower. Park Tool’s Chain Compatibility page is a solid cross-check when you want current fit notes before ordering.

One thing the chart makes plain is that the inside width does not change as much as many riders think. What really shrinks on modern geared chains is the outside width. That is why a chain may look close by eye and still shift badly once you start riding.

Chain Length Is Part Of Size Too

Width is only half the story. A new chain also has to be the right length for your bike. Most new chains are sold long on purpose, often 114 to 126 links, so the mechanic or rider can cut them to fit. That means “bike chain size” is not just width. It is width plus final chain length on your frame and gearing.

If you copy the old chain link for link, you may copy old wear too. A worn chain gets longer over time. That is why sizing from the drivetrain is safer than matching a stretched chain laid on the floor. Shimano’s How to Check Your Chain Length article shows the common big-chainring and big-sprocket method that many home mechanics use.

Bike Setup	Common New Chain Length Sold	What Usually Happens At Install
Single-speed, BMX, track	96 to 114 links	May fit as sold or need a small trim, based on axle position and chainstay length.
6/7/8/9-speed bikes	114 or 116 links	Often shortened to suit wheelbase and gear size.
10-speed road or hybrid	114, 116, or 118 links	Usually trimmed, then closed with the right joining pin or master link.
11-speed road or gravel	116 or 118 links	Trim length is common, especially on compact frames and wide-range cassettes.
12-speed mountain or gravel	118, 122, or 126 links	Wide-range cassettes often need more links before final trimming.
Long-tail Or Full-Suspension E-Bike	122 or 126 links	Long rear centers and suspension movement often call for more chain than a standard bike.

Mistakes That Ruin A Good Chain Swap

A wrong purchase usually comes from one of a few habits:

• Buying by wheel size instead of drivetrain speed.
• Mixing a single-speed chain with derailleur parts.
• Assuming all 12-speed chains fit all 12-speed cassettes.
• Reusing the wrong master link.
• Cutting the chain to match an old worn chain.
• Ignoring worn chainrings or a badly worn cassette.

If a fresh chain skips under load on the old cassette right away, the cassette may already be worn to match the old chain. In that case, the chain size may be right and the worn cogs are the real issue.

What To Measure When You Are Still Not Sure

If the bike is old, custom, or built from mixed parts, use a short checklist. Count the rear cogs. Measure the rear cog and chainring tooth width if it is single-speed. Read the model name on the derailleur or cassette if it is a geared bike. Then compare that with the chain description on the box.

You can skip the math on pitch, pin diameter, and plate shaping unless you are building a rare drivetrain. For everyday replacement work, the right speed family and the right final length do almost all the heavy lifting. Once those two pieces are right, the rest of the job gets much easier.

What This Means For Your Next Chain Buy

Most riders need only three facts: single-speed or geared, how many rear cogs, and whether the bike uses a brand-specific 12-speed chain. Nail those, and the choice gets much easier. Then cut the chain to the right length, use the matching connector, and your drivetrain has a much better shot at running quiet and clean from the first ride.

If you want the safest shopping habit, buy the chain that matches the cassette speed and drivetrain family first, then trim the length at install. That one habit avoids most chain-size mistakes and keeps you away from the usual mix-ups that waste money and riding time.