ANSI Roller Chain Dimensions: Pitch, Roller Diameter, Width, and Pin Charts

ANSI roller chain dimensions are the set of physical values, namely pitch, roller diameter, inner width, pin diameter, plate height, overall width and transverse pitch, that decide whether a chain seats correctly on a sprocket and survives the load you calculated for it.

A #40 chain and an ISO 08B chain both measure 12.70 mm pitch. Their rollers measure 7.92 mm and 8.51 mm. Fit the 08B on a #40 sprocket and the roller rides high in the tooth root, contact shifts from a broad seating arc to two narrow points, and the sprocket takes a visible step long before the chain reaches its rated life. That single example explains why a dimension chart matters more than a part number on a purchase order.

What the Core ANSI Dimensions Actually Control

Each dimension answers a separate engineering question: pitch fixes sprocket geometry, roller diameter fixes seating and articulation, inner width fixes lateral clearance, pin diameter fixes bearing pressure, and plate height fixes the tensile area available in the link plates.

• Pitch (p). Centre distance between adjacent pin centres. It has to match sprocket pitch closely; a chain that runs a few hundredths long or short loads one tooth at a time and runs noisy.
• Roller diameter (d1). Sets how deep the roller sits in the tooth root and how far it slides as the joint articulates. An undersized roller raises sliding speed on the tooth flank.
• Inner width (b1). The clear gap between inner plates. Too narrow and the sprocket tooth rubs the plates; too wide and the chain wanders across the tooth.
• Pin diameter (d2). Determines bearing area inside the bushing, which is where most fatigue cracks begin on reversing or high-shock drives.
• Plate height (h2). Used for outside clearance checks and for estimating tensile area. Heavy series chains raise it without touching pitch or roller size.
• Overall width (b2) and transverse pitch (pt). The two numbers that decide whether a chain fits an existing housing or a multi-strand sprocket set.

Reading the Chain Number Instead of Measuring It

The ANSI number is built from two parts: the leading digits multiplied by 1/8 in give the pitch, and the final digit gives the chain type.

A worked example is #60. Six eighths is 0.750 in, or 19.05 mm pitch, matched to an 11.91 mm roller. Add the H suffix and you have #60H: same pitch, same roller, thicker plates, roughly 20 to 25 percent more tensile strength. That gap matters at replacement time. If a drive was sized around an H-series chain and someone fits the standard version, the chain becomes the weakest component in the system.

The final digit is the other common trap. A zero marks a standard roller chain, a one marks a lightweight version with thinner plates, and a five marks a bushing chain without rollers for slow or abrasive duties. A #41, for instance, runs on #40 sprockets but carries noticeably less load, so it is a service part rather than a like-for-like swap.

For the application side of the same data, the site's ANSI chain dimension and selection guide walks through drive and conveyor examples using these same values.

A-Series Short-Pitch Precision Roller ChainSingle-strand ANSI A-series chain from #25 to #240, with metric and inch dimensions and tensile data for drive and conveyor selection.View Product →

Standard ANSI Roller Chain Dimension Chart

The table lists single-strand ANSI roller chain dimensions from #25 to #240, with metric values first and inch equivalents in brackets.

Strength climbs faster than pitch. Moving from #40 to #80 multiplies minimum ultimate strength by roughly 3.7, which is why a modest step up in chain size so often solves an overload that lubrication and tensioning cannot.

Strands, Transverse Pitch, and the ANSI versus ISO Split

Multi-strand ANSI chain keeps the single-strand pitch and roller diameter and adds one transverse pitch for every extra strand, while ISO B-series chain shares some imperial pitches but not the roller or width dimensions.

Apart from pitch, nothing on these two chains is interchangeable. Mixed plants running American and European equipment are where this goes wrong most often, and the failure is quiet: the chain runs, wears fast, and takes the sprockets with it.

Transverse pitch for common multi-strand sizes:

• #40: 14.38 mm
• #50: 18.11 mm
• #60: 22.78 mm
• #80: 29.29 mm
• #100: 35.76 mm

B-Series Short-Pitch Precision Roller ChainSingle-strand B-series chain from SS04B-1 to SS48B-1, with pitch, roller, pin and tensile data for precision drive and conveyor applications.View Product →

Using the Same Numbers to Check Wear and Sprocket Fit

The dimensions that guide selection also work as a wear gauge: measure pitch across ten links, compare roller diameter with the chart, and you have a replacement trigger that beats any visual inspection.

1. Measure ten pitches. Put a caliper across eleven pin centres and divide by ten; the difference from nominal pitch is your elongation.
2. Convert to a percentage. Around 1.5 percent is the usual replacement point for drive chain. Beyond 2 percent the sprocket teeth have already been reshaped, and a new chain will run badly on them.
3. Check roller diameter. A roller worn below the chart value lets the chain sit deeper in the tooth root, which usually shows up as vibration before it shows up as elongation.
4. Confirm outside clearance. Plate height plus roller radius sets the envelope, so an H-series chain on a tight sprocket can foul a housing that a standard chain cleared.
5. Match sprocket tooth width to inner width. A tooth half a millimetre too wide rubs the inner plates and produces the grey paste that gets reported as the chain wearing out.

Industrial Sprockets for Chain TransmissionSprockets in flat, hub and assembly types, with stainless steel and custom options, matched to chain pitch and roller diameter for reliable transmission.View Product →

A worn sprocket will ruin a new chain within weeks, so chain and sprocket are best ordered together once pitch and roller diameter are confirmed.

Frequently Asked Questions

How do I identify an ANSI roller chain by measuring it?

Measure across eleven pin centres and divide by ten for the pitch, then measure roller diameter with a caliper. A 12.70 mm pitch with a 7.92 mm roller is #40, while the same pitch with an 8.51 mm roller is an ISO 08B chain.

Are ANSI and ISO roller chains interchangeable?

Only at the pitch level, and even that is not universal across every size. Roller diameter, inner width and pin diameter differ, so a chain from one standard will not seat properly on sprockets cut to the other.

What does the H suffix mean in ANSI chain sizes?

Heavy series. Pitch and roller diameter stay the same, the link plates are thicker, and minimum tensile strength is typically 20 to 25 percent higher than the standard part carrying the same number.

How much elongation is acceptable before replacement?

About 1.5 percent for most drive applications, measured over ten or more pitches. Past 2 percent, sprocket wear accelerates quickly and the chain's fatigue life is largely spent.

What is the largest standard ANSI roller chain?

#240, with a 76.20 mm (3 in) pitch, a 47.63 mm roller and a minimum ultimate tensile strength near 534 kN.