Roller chain sizes: 06B, 08B, 10B and 12B vs ANSI 35, 40, 50 and 60 (simplex, duplex and stainless)

Simplex roller chain is single-strand chain: 06B-1, 08B-1, 10B-1 and 12B-1 have pitches of 9.525, 12.7, 15.875 and 19.05 mm (3/8", 1/2", 5/8", 3/4"), and the -2 versions are duplex, with two strands. ANSI 35, 40, 50 and 60 share those pitches but are different chains. We sell 08B-1 simplex chain and the rest in 10 ft boxes.

If you already know your chain's number, you can stop here and pick it from the list further down. If you don't, the table and the measuring steps tell you which one you have.

Industrial roller chain sizes: B-series vs ANSI (mm)

Source: chain makers' published B-series and ANSI chain tables (see Sources), read 28 September 2026. Where a cell shows a range, the makers' figures differ and the range covers both. Tensile figures are the ISO 606 minimums; one maker gives the same four B-series figures and quotes higher ANSI-standard minimums for 35, 40, 50 and 60 (8.7, 15.2, 24.0 and 34.2 kN).

B-series and ANSI chain of the same pitch are not interchangeable

Every roller chain is classified by three measurements: pitch (the distance between the centres of neighbouring pins), roller diameter and the width between the inner plates. Together these determine the form and width of the sprocket teeth. Same pitch is only one of the three. 08B-1 and ANSI 40 both have a 12.7 mm pitch, but the 08B roller is 8.51 mm and the ANSI 40 roller is 7.92 mm, and the 08B pin is thicker (4.45 vs 3.97 mm). Treat them as different chains with different sprockets.

The part that gives a chain away changes with the size:

• 06B vs ANSI 35: ANSI 35 is a bush chain, so it has no rollers. It is also narrower inside: 4.68 to 4.78 mm against 5.72 mm.
• 08B vs ANSI 40: measure the roller. 8.51 mm is 08B; 7.92 mm is ANSI 40. The inside widths are within 0.2 mm of each other, too close to rely on.
• 10B vs ANSI 50: the closest pair. Same pitch, same 10.16 mm roller. The plates give it away: ANSI 50 plates are 2.0 mm thick against 1.5 mm on 10B, and 10B is slightly wider inside (9.65 vs 9.40 to 9.53 mm). Chain makers still list them as separate chains, so treat them as two different chains.
• 12B vs ANSI 60: measure inside the inner plates. 12B is 11.68 mm and ANSI 60 is 12.57 to 12.70 mm, about 1 mm wider, with thicker plates (2.4 vs 1.8 mm).

Why this matters here: chain makers list Australia, with the USA, Canada and Japan, among the places American-standard chain is mainly used, and the British Commonwealth among the places European (B-series) chain dominates. In practice, Australian machines carry both, so don't assume. Check the plates first: BS and ISO standards require the chain series to be marked on the chain.

How to measure roller chain size

You need vernier callipers (a steel rule will do for step 2).

1. Look for a marking. Check the outer plates for a stamped number such as 08B or 40. If it's there and readable, you're done.
2. Measure the pitch over three pitches. Measure from the centre of one pin to the centre of the pin three along (four pins, three gaps), then divide by 3. Three pitches of 06B/35 are 28.6 mm, of 08B/40 are 38.1 mm, of 10B/50 are 47.6 mm and of 12B/60 are 57.2 mm. Measuring over several pitches averages out small errors, and it still works on a worn chain: chain makers' guidance is to replace a chain at 2% stretch, which is only about 0.8 mm over three 1/2" pitches.
3. Measure the roller diameter. Close the callipers across one roller. This separates 08B from ANSI 40, and tells you whether a 3/8" chain has rollers at all.
4. Measure the inside width. Measure between the two inner plates of one inner link. This separates 12B from ANSI 60 and 06B from ANSI 35.
5. Measure an inner plate's thickness if you have a 5/8" chain. About 1.5 mm is 10B; about 2.0 mm is ANSI 50.
6. Count the strands. One row of rollers is simplex (-1). Two rows side by side is duplex (-2).
7. Check the result against the table. If your 1/2" chain measures well under 7.75 mm inside, it's a narrower chain again, not 08B or ANSI 40 (see the #415 question below).

Simplex, duplex and stainless: what the suffix and material change

Simplex (-1) and duplex (-2). The numbering: the first two digits of a B-series chain are the pitch in sixteenths of an inch (08 = 8/16 = 1/2"), the B means European standard, and the suffix is the number of strands. ANSI numbers the pitch in eighths (40 = 4/8 = 1/2"); a 5 in place of the 0 means a bush chain, as in 35. A duplex chain has the same pitch, roller and inside width as the simplex, with two strands side by side. On 08B-2 the strands are 13.92 mm apart and the chain is rated at 31.1 kN minimum, against 17.8 kN for 08B-1. A duplex chain runs on a duplex sprocket: simplex, duplex and triplex sprockets are listed separately for each B-series pitch.

Stainless. Our stainless chain comes in 06B-1 and 08B-1, and the listings describe it as British Standard size, so it measures like the steel chain of the same number. Chain makers list their stainless B-series chain with the same pitch, roller and inside width as their carbon steel chain. It is weaker: one maker's catalogue puts its stainless chain at approximately 65% of the tensile strength of standard carbon steel chain, and lists its stainless 08B-1 at 12.0 kN against 17.8 kN for the steel 08B-1. Stainless suits chain that meets water, acids, alkalis or food, or very high or low temperatures. Pick stainless for corrosion, not for load.

Joining the chain. Every box of ours contains one connecting link. Chain makers advise designing the drive for an even number of pitches, so a standard connecting link closes it; a cranked (half) link is only for an odd number of pitches, and should not be used on impulsive, highly loaded or high-speed drives. Spare connecting links aren't listed on our website, but we sell them on request.

Which BES chain fits

All of these are 10 ft boxes with one connecting link.

• Pick 06B-1 simplex if your chain has rollers, a 9.525 mm pitch and 5.72 mm inside.
• Pick 08B-1 simplex if the pitch is 12.7 mm and the roller measures 8.51 mm.
• Pick 10B-1 simplex for a 15.875 mm pitch with 1.5 mm plates.
• Pick 12B-1 simplex for a 19.05 mm pitch with 11.68 mm inside.
• Pick 06B-2 duplex or 08B-2 duplex if your chain has two strands.
• Pick stainless 06B-1 or stainless 08B-1 if the chain lives in water, a wash-down area or food handling, and the load allows for the lower strength.
• Pick our ASA chain if you measured an American-standard chain: ASA 40-1R 1/2" for a 7.92 mm roller, ASA 50-1R 5/8" for 2.0 mm plates, and ASA 60-1R 3/4" for about 12.6 mm inside.
• Pick the Cox drive and steering chain AM018 / #415H for the Cox, Stockman and SupaNova ride-ons it lists, not a length of 08B.

See all of them in chain.

Questions people also ask

What are the 08B chain dimensions?

08B-1 is 12.7 mm (1/2") pitch, 8.51 mm roller diameter, 7.75 mm between the inner plates and 4.45 mm pin diameter, with a minimum tensile strength of 17.8 kN.

What are the 06B chain dimensions?

06B-1 is 9.525 mm (3/8") pitch, 6.35 mm roller, 5.72 mm inside width and 3.27 to 3.28 mm pin, with an 8.9 kN minimum tensile strength.

Is 08B the same as 40 chain?

No. Both have a 12.7 mm pitch, but 08B has an 8.51 mm roller and 4.45 mm pin, and ANSI 40 (40-1) has a 7.92 mm roller and 3.97 mm pin. Roller diameter and inside width set the sprocket tooth form, so match the standard you have.

What is 5/8 chain?

5/8" is the pitch, 15.875 mm. It could be 10B (B-series) or ANSI 50: both have a 10.16 mm roller, so check the plate thickness, about 1.5 mm on 10B and 2.0 mm on ANSI 50.

Is #415 chain the same as 08B?

No. Our Cox #415H chain has a 1/2" (12.7 mm) pitch like 08B, but only 3/16" (about 4.8 mm) between the plates, against 7.75 mm on 08B. It is sold as 86 links including the connecting link.

What is the difference between simplex and duplex chain?

Simplex has one strand of rollers, duplex has two side by side on longer pins. Pitch, roller and inside width are the same, and duplex 08B-2 is rated at 31.1 kN minimum against 17.8 kN for simplex 08B-1.

Related reading

• UCP204, UCP205 and UCP206 pillow block dimensions, for the shaft bearings a chain drive usually runs on
• Bearing size chart 6000 to 6310

Sources

• Renold, Renold Roller Chain, Premier standard chain tables: European (BS) Standard simplex, duplex, triplex and ANSI Standard simplex, duplex (renold.com/media/228840/renold-brand-chain-tables.pdf), read 28 September 2026.
• Renold, Transmission Chain Product catalogue REN1 ENG 07.14: chain classification and connecting links (p. 7), stainless steel chain (p. 10), stainless steel chain tables (p. 20), sprockets (Section 3) (renold.com/media/165414/transmission-chain-ren1-eng-07-14.pdf), read 28 September 2026.
• Renold, Chain Designer Guide: International Standards (p. 97) and chain wear (p. 114) (renold.com/upload/renoldswitzerland/roller_chain_designer_guide.pdf), read 28 September 2026.
• Renold, Chain Standards (renold.com/support/chain-info-index/chain-standards/), read 28 September 2026.
• Tsubaki Europe, Catalogue 1 Drive Chain: basic parts (p. 8), BS Runner (p. 15), BS SS chain (p. 18), ANSI G7 (p. 25) (tsubaki.eu/assets/CAT_1_herdruk_compleet.pdf), read 28 September 2026.
• Tsubaki Europe, BS/ANSI chain identification sheet (tsubaki.eu/assets/BS-ANSI Identification sheet.pdf), read 28 September 2026.

Checked against the Renold and Tsubaki catalogues above and BES product data on 28 September 2026.