Roller Chain Size Chart

How to measure roller chain correctly

Clean the chain and measure an unloaded, straight section after the machine has been safely isolated. Use a caliper for the roller and clear inner width. Read any side-plate markings and record the number of strands; those details can distinguish versions that a single pitch measurement cannot.

1. Pitch: measure between equivalent pin centres. Measuring several pitches and dividing by the number of spaces reduces reading error. Six pins contain five pitch spaces, not six.
2. Roller diameter: measure across a roller’s outside surface. For #25 and #35 in this table, the exposed part is a bush because the chain has no rollers.
3. Inner width: measure the clear gap between the inner plates, not the overall pin length or the outside plate-to-plate width.

U.S. Tsubaki’s measurement guide describes this identification method. Wear can shift measurements, so confirm a promising result with a marking, an unworn sample or the machine’s parts list.

Do not assume a multi-strand chain is single-strand. The same basic link dimensions can be used in -1, -2, and -3 versions, but transverse pitch, overall width and matching sprocket selection differ. How to read strand designations.

ANSI vs ISO B: equal pitch does not mean the same chain

Common ANSI numbers encode familiar inch pitches: #40 is 4/8 in., #50 is 5/8 in., #60 is 6/8 in., and #80 is 8/8 in. B-series names use another designation: 08B, 10B, 12B and 16B have those same respective pitches. The remaining dimensions can differ.

The identification tool deliberately permits multiple candidates where ordinary measurements cannot reliably resolve them. For example, #50 and 10B have the same listed roller diameter and very close inner widths. Use the full product documentation rather than treating a tiny measurement difference as proof. Source: Tsubaki ANSI and B-series tables.

Read the full designation before ordering

A basic size does not specify every feature. A suffix such as -1, -2 or -3 identifies single, double or triple strand in the manufacturer tables. Multi-strand chain requires the correct transverse spacing and matching sprocket. Multiplying the single-strand inner width does not give the complete chain width.

Heavy-duty, stainless, corrosion-resistant, sealed, hollow-pin and attachment chains can share selected dimensions while having different plates, pins, lubrication requirements and allowable operating conditions. Connecting links also belong to the specific product series. An existing offset link or an odd pitch count should be reported when ordering because that construction can affect selection and rating.

The U.S. Tsubaki sizing guide identifies pitch, roller diameter and the gap between inner plates as essential measurements; the manufacturer catalogue also lists pins and plate dimensions used when evaluating a specific construction. Use this chart for size-family identification, then confirm the full part designation and sprocket before purchase. Bicycle and motorcycle numbering systems, double-pitch conveyor chain and specialty chains are outside this chart.

Worked example: identify a half-inch-pitch chain

A measured chain spans 63.50 mm across five pitches. Divide by five to get 12.70 mm (0.500 in.). That pitch matches ANSI #37, #38, #41 and #40 and ISO 08B-1 in this catalogue. Use the inner plate gap and roller size to distinguish them.

Next, suppose the roller measures about 7.92 mm and the gap between the inner plates about 7.95 mm. Those values point to #40 in the cited Tsubaki table. The lighter #41 has a narrower 6.38 mm inner width. The 08B roller is larger at 8.51 mm. Check the side-plate marking and sprocket specification before confirming the order.

If the roller and width cannot be measured accurately, clear those optional fields rather than entering zero. The lookup will show the pitch candidates without pretending it has identified one unique chain. A measured size beyond the lookup window may indicate wear, a measurement error, or a chain family outside the table.

Measure wear separately from nominal chain size

Wear between pins and bushings increases the effective pitch over a chain length. A worn #40 chain does not become a different nominal chain size. Measure over several pitches under the conditions required by the manufacturer and compare the measured span with the nominal span:

Wear elongation (%) = (measured span − nominal span) ÷ nominal span × 100.

For example, ten nominal 12.70 mm pitches total 127.00 mm. A measured 128.27 mm span corresponds to 1.0% elongation. Count the pitch spaces carefully and avoid using a slack, curved span. This arithmetic is a wear estimate, not a complete inspection.

U.S. Tsubaki’s measurement guide explains wear elongation and describes a typical 1.5–2% replacement range, but inspection and replacement limits vary by chain, drive, and manufacturer. Follow the applicable equipment specification, including cases requiring earlier replacement. Inspect sprockets, alignment, tension and lubrication together.

Why this dimension chart does not provide a working-load rating

Tensile strength is a destructive-test quantity; it is not the allowable continuously repeated load for a chain drive. Rated service depends on the specific chain construction, speed, sprocket size, lubrication, shock, starts and stops, environment and other selection factors. A chain that fits geometrically can still be unsuitable for the application.

Tsubaki’s chain-structure guidance distinguishes the roles of the plates, pins, bushes and rollers. The plates carry repeated tensile loads, while the pin-and-bush joints articulate. Their material treatment and fatigue performance cannot be inferred from pitch alone.

Use the chain manufacturer’s drive-selection procedure for a new design. For maintenance, retain the machine’s specified product or obtain an approved equivalent with the necessary dimensions and ratings. The table is intended for identification and comparison; it is not a lifting-chain selection tool or a justification for bypassing a machine’s part specification.

Roller Chain Size Chart FAQs

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