Order the wrong roller chain and you find out within the first few hours of running it — it rides high on the sprocket teeth, throws slack under load, or the master link simply won’t close. Almost every one of those failures traces back to the same root cause: someone matched the wrong pitch, or measured a worn chain against a fresh-chain dimension.
This chart lists the exact pitch, roller diameter, pin diameter, plate thickness, and minimum tensile strength for all 14 standard ANSI B29.1 chain sizes, from #25 up to #240, plus the four measurements that let you identify a chain even after its stamp has worn off.
Reading a Chain Number: What 40, 41, and 60H Actually Tell You
Chain pitch is the center-to-center distance between two consecutive pins on a roller chain — the single dimension that determines whether a given chain will mesh with a given sprocket.
ANSI roller chain numbers aren’t arbitrary. The digits ahead of the last one give the pitch in eighths of an inch: a #40 chain has a 4/8", or 1/2" (12.70 mm), pitch; a #120 chain steps up to 12/8", or 1.5" (38.10 mm).
The last digit carries its own meaning. A 0 marks a standard roller chain. A 5 — as in #25 and #35 — means the chain has no rollers at all; the roller position is filled by a plain bushing, which is why ASME B29.1 lists a “bushing diameter” instead of a roller diameter for those two sizes. A 1, as in #41, denotes a lightweight riveted-pin chain that skips the separate bushing entirely — it shares #40’s 1/2" pitch but isn’t built to the same dimensional standard, and it is not a drop-in substitute (see the FAQ below).
An “H” suffix (60H, 80H) means heavy series — same pitch and roller diameter as the standard chain, thicker link plates. A hyphenated number (60-2, 60-3) tells you the strand count: duplex, triplex, and so on, running side by side on a wider, matching sprocket.
Quick Pitch Reference
#25 — 1/4" (6.35 mm)
#35 — 3/8" (9.53 mm)
#40 / #41 — 1/2" (12.70 mm)
#50 — 5/8" (15.88 mm)
#60 — 3/4" (19.05 mm)
#80 — 1" (25.40 mm)
#100 — 1-1/4" (31.75 mm)
#120 — 1-1/2" (38.10 mm)
#140 — 1-3/4" (44.45 mm)
#160 — 2" (50.80 mm)
#180 — 2-1/4" (57.15 mm)
#200 — 2-1/2" (63.50 mm)
#240 — 3" (76.20 mm)
How to Measure a Roller Chain in 4 Steps
If the stamp on the outer plate is gone — corrosion, grinding, or years of grease will do that — four measurements will get you to the right chain number.
Pitch — center-to-center distance between pins, measured across 10–12 pitches under the chain’s rated measuring load, then divided by the pitch count. Measuring a single pitch amplifies any wear into a false reading; spreading the measurement out averages it away.
Roller diameter — the outside diameter of the roller (or bushing, on #25/#35) at its widest point, measured with calipers.
Width between plates — the gap the sprocket tooth sits in, measured at the inner link, not across the outer plates.
Pin diameter — measured through the plate hole. Small differences here (0.156" for #40 vs. 0.141" for #41) are what separate chains that otherwise look identical.
Cross-check all four numbers against the chart below — pitch alone isn’t enough to confirm a size, since #40, #41, and the metric 08B chain all share the same 1/2" pitch.
ANSI Roller Chain Size Chart (ASME B29.1-2011)
Dimensions below are for standard-series, single-strand chain. Roller diameter, width, and pin diameter are the maximum/nominal values specified in ASME B29.1-2011.
Chain No. | Pitch | Max. Roller Dia. | Width Between Plates | Pin Dia. | Plate Thickness (Std.) | Min. Tensile Strength |
|---|---|---|---|---|---|---|
#25 | 0.250" (6.35 mm) | 0.130" (3.30 mm) | 0.125" (3.18 mm) | 0.0905" (2.30 mm) | 0.030" (0.76 mm) | 780 lb (3.5 kN) |
#35 | 0.375" (9.53 mm) | 0.200" (5.08 mm) | 0.188" (4.78 mm) | 0.141" (3.58 mm) | 0.050" (1.27 mm) | 1,760 lb (7.8 kN) |
#40 | 0.500" (12.70 mm) | 0.312" (7.92 mm) | 0.312" (7.92 mm) | 0.156" (3.96 mm) | 0.060" (1.52 mm) | 3,125 lb (13.9 kN) |
#41 | 0.500" (12.70 mm) | 0.306" (7.77 mm) | 0.250" (6.35 mm) | 0.141" (3.58 mm) | 0.050" (1.27 mm) | 1,500 lb (6.7 kN) |
#50 | 0.625" (15.88 mm) | 0.400" (10.16 mm) | 0.375" (9.53 mm) | 0.200" (5.08 mm) | 0.080" (2.03 mm) | 4,880 lb (21.7 kN) |
#60 | 0.750" (19.05 mm) | 0.469" (11.91 mm) | 0.500" (12.70 mm) | 0.234" (5.94 mm) | 0.094" (2.39 mm) | 7,030 lb (31.3 kN) |
#80 | 1.000" (25.40 mm) | 0.625" (15.88 mm) | 0.625" (15.88 mm) | 0.312" (7.92 mm) | 0.125" (3.18 mm) | 12,500 lb (55.6 kN) |
#100 | 1.250" (31.75 mm) | 0.750" (19.05 mm) | 0.750" (19.05 mm) | 0.375" (9.53 mm) | 0.156" (3.96 mm) | 19,530 lb (86.9 kN) |
#120 | 1.500" (38.10 mm) | 0.875" (22.23 mm) | 1.000" (25.40 mm) | 0.437" (11.10 mm) | 0.187" (4.75 mm) | 28,125 lb (125.1 kN) |
#140 | 1.750" (44.45 mm) | 1.000" (25.40 mm) | 1.000" (25.40 mm) | 0.500" (12.70 mm) | 0.219" (5.56 mm) | 38,280 lb (170.3 kN) |
#160 | 2.000" (50.80 mm) | 1.125" (28.58 mm) | 1.250" (31.75 mm) | 0.562" (14.27 mm) | 0.250" (6.35 mm) | 50,000 lb (222.4 kN) |
#180 | 2.250" (57.15 mm) | 1.406" (35.71 mm) | 1.406" (35.71 mm) | 0.687" (17.45 mm) | 0.281" (7.14 mm) | 63,280 lb (281.5 kN) |
#200 | 2.500" (63.50 mm) | 1.562" (39.67 mm) | 1.500" (38.10 mm) | 0.781" (19.84 mm) | 0.312" (7.92 mm) | 78,125 lb (347.5 kN) |
#240 | 3.000" (76.20 mm) | 1.875" (47.63 mm) | 1.875" (47.63 mm) | 0.937" (23.80 mm) | 0.375" (9.53 mm) | 112,500 lb (500.4 kN) |
#25 and #35 “Max. Roller Dia.” values are bushing diameters — these two sizes have no rollers. Heavy-series (H) plate thickness runs one increment thicker than shown; multi-strand tensile strength scales from these single-strand figures (see the FAQ for the real-world multiplier).
ANSI vs. ISO/BS: Matching Pitch Doesn’t Mean Matching Fit
The ISO/BS metric system runs in parallel to ANSI, and five common sizes happen to share pitch with their ANSI counterpart. That doesn’t make them interchangeable — roller diameter and inner width both shift enough to affect sprocket engagement.
ANSI Chain | Pitch | ANSI Roller Dia. | ANSI Width | BS/ISO Equivalent | BS Roller Dia. | BS Width |
|---|---|---|---|---|---|---|
#40 | 12.70 mm | 7.92 mm | 7.95 mm | 08B-1 | 8.51 mm | 7.75 mm |
#50 | 15.875 mm | 10.16 mm | 9.53 mm | 10B-1 | 10.16 mm | 9.65 mm |
#60 | 19.05 mm | 11.91 mm | 12.70 mm | 12B-1 | 12.07 mm | 11.68 mm |
#80 | 25.40 mm | 15.88 mm | 15.88 mm | 16B-1 | 15.88 mm | 17.02 mm |
#100 | 31.75 mm | 19.05 mm | 19.05 mm | 20B-1 | 19.05 mm | 19.56 mm |
An ANSI #40 sprocket, for instance, is cut for a 7.92 mm roller riding in a 7.95 mm gap. Drop an 08B chain onto it and the 8.51 mm roller has to seat in a slot never sized for it — it may thread on, but engagement will be off enough to accelerate wear on both chain and sprocket. If you’re replacing chain on imported equipment, confirm which standard the existing sprocket was cut to before ordering — our ANSI vs. ISO sprocket replacement guide walks through that identification process in detail.
Standard vs. Heavy Series, Single vs. Multi-Strand
The “H” suffix (#60H, #80H) marks heavy series: identical pitch and roller diameter to the standard chain of that size, with thicker link plates for added fatigue resistance — a strength upgrade that doesn’t require a different sprocket. A hyphenated number after the base size (60-2, 60-3, 60-4) gives the strand count — duplex, triplex, quadruplex — with each strand riding parallel on a matching multi-strand sprocket.
ASME B29.1 defines multi-strand minimum tensile strength as an exact multiple of the single-strand rating — a 60-3 is rated at 3 × 7,030 lb, or 21,090 lb minimum — though the horsepower rating you’d actually design a drive around uses a smaller, non-linear multiplier (covered in the FAQ).
Every chain size in this chart pairs with a matching ANSI sprocket — tooth form, bore, and pitch diameter all follow from the numbers above. Lily Bearing stocks ANSI roller chain from #25 through #160 in single- and double-strand configurations, including standard, high-strength corrosion-resistant, and double-pitch lines.
Once the size is confirmed, tooth count and ratio are the next decision — see our sprocket ratio selection guide. For installation, tensioning, and lubrication after the chain is on, our chain and sprocket maintenance guide covers that ground.
Frequently Asked Questions
What’s the difference between #40 and #41 roller chain?
Both share a 1/2" (12.70 mm) pitch, but they’re built to different standards and aren’t interchangeable. #41 is a lightweight, riveted-pin chain without a separate bushing — more like a heavy-duty bicycle chain than a true bushing roller chain. Its minimum tensile strength is 1,500 lb, versus 3,125 lb for standard #40, and its roller (0.306") and width (0.250") both run narrower than #40’s (0.312" and 0.312"). #41 shows up on go-karts and light single-sprocket setups; #40 is the general industrial standard.
Does a higher tensile-strength number mean the chain is stronger for my application?
Not directly. Minimum ultimate tensile strength (MUTS) is a destructive break-test figure, not a usable working load. Industry guidance generally caps working load at 1/6 of average tensile strength for chain joined with press-fit connecting links, or 1/9 for slip-fit or offset links — and manufacturers note there’s no consistent relationship between a chain’s working-load capacity and its listed tensile strength across brands. Size a chain from the manufacturer’s horsepower/working-load table for your RPM and tooth count, not by comparing raw MUTS numbers between chains.
How much more load can a duplex or triplex chain actually carry?
Less than a straight multiple of the strand count. While MUTS scales linearly (a 3-strand chain rates at exactly 3× the single-strand figure), the practical multi-strand factor used in horsepower tables accounts for uneven load-sharing across strands: 1.7× for duplex, 2.5× for triplex, 3.3× for quadruplex, 3.9× for 5-strand, and 4.6× for 6-strand. A 60-3 chain, in other words, isn’t rated for triple the horsepower of a 60-1 — closer to 2.5 times.
My chain’s stamped size doesn’t match any dimension in this chart — what’s going on?
Three common explanations. First, it may be a double-pitch chain (common on conveyors) — these use the same roller and pin dimensions as a smaller ANSI size but at twice the pitch, so a C2040 double-pitch chain shares #40’s roller and pin but spaces them at 1" instead of 1/2".
Second, it could be built to JIS, DIN, or an oilfield-specific standard rather than ANSI or BS/ISO.
Third, if the chain is worn, a pitch measurement taken across too few pitches will read long and won’t match any nominal size — remeasure across 10–12 pitches per the method above.
At what point should I replace a chain instead of just re-tensioning it?
When wear elongation reaches roughly 3% of nominal length for most industrial drives, or about 1.5% on drives with fixed center distances or where smoother operation matters. A more precise version of the same rule is 200 ÷ N, where N is the tooth count on the large sprocket — useful because it's only valid up to 67 teeth, past which the flat 3% figure applies. Re-tensioning a chain that's already past this point doesn't fix the underlying wear; it just delays a failure that's now more likely to take the sprocket teeth down with it.
Looking for more than just ANSI roller chain? Browse the full chain and sprockets catalogs for metric, attachment, and specialty options across the rest of the drive.
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