User Rating 0.0 ★★★★★

Total Usage 0 times

Category Engineering Calculators

Chain Type

Pitch (mm) Distance between pin centers

Unit

Small Sprocket Teeth (T₁)

Large Sprocket Teeth (T₂)

Center Distance (mm) Shaft-to-shaft distance

Chain Type

Pitch (mm)

Unit

Number of Links Must be a positive even integer for standard roller chain

Results

Is this tool helpful?

Your feedback helps us improve.

★ ★ ★ ★ ★

About

Incorrect chain length causes premature wear, sprocket damage, and catastrophic drive failure. A chain that is even one link too short generates excessive tension that accelerates fatigue cracking. A chain one link too long produces slack that allows skipping under load. This calculator determines precise chain length L from sprocket tooth counts T₁ and T₂, pitch P, and center distance C using the standard two-sprocket drive equation. It rounds the result to the nearest even link count, as roller chains require an even number of links to close properly without an offset (half) link. The tool assumes parallel shaft alignment and no chain sag correction. For drives with significant sag (vertical or long-span horizontal), add 1 - 2% to the calculated length.

Supported standards include ANSI (American National Standards Institute) roller chain series from #25 through #240 and ISO (International Organization for Standardization) equivalents. Pitch values range from 6.35 mm (#25) to 76.2 mm (#240). The calculator also handles bicycle and motorcycle chain pitches. Pro tip: always verify the manufacturer's minimum wrap angle of 120° on the smaller sprocket before finalizing center distance.

Formulas

The chain length for a two-sprocket drive is calculated in units of pitches, then converted to a linear measurement. The standard equation from ANSI B29.1 is:

L_pitches = 2CP + T₁ + T₂2 + P(T₂ − T₁)²4π²C

The total physical chain length is then:

L = N × P

Where N is the number of links rounded up to the nearest even integer. The exact center distance for a given even link count N is found by solving the quadratic derived from the equation above:

C = P4 × [ A + √A² − 8(T₂ − T₁)²π² ]

Where A = 2N − T₁ − T₂.

Variable definitions: L = total chain length. P = chain pitch (distance between pin centers). C = center distance between sprocket shafts. T₁ = number of teeth on the smaller sprocket. T₂ = number of teeth on the larger sprocket. N = number of links (always even for standard roller chain).

Reference Data

Chain Number	ISO Equivalent	Pitch P	Roller Diameter	Pin Diameter	Inner Width	Tensile Strength	Weight per Meter	Common Use
#25	04C	6.35 mm	3.30 mm	2.30 mm	3.18 mm	3.6 kN	0.15 kg/m	Small instruments, robotics
#35	06C	9.525 mm	5.08 mm	3.58 mm	4.77 mm	8.0 kN	0.33 kg/m	Go-karts, light machinery
#40	08A	12.70 mm	7.92 mm	3.97 mm	7.85 mm	14.1 kN	0.62 kg/m	Agricultural, conveyor
#41	-	12.70 mm	7.77 mm	3.58 mm	6.25 mm	6.7 kN	0.42 kg/m	Lightweight #40 alternative
#50	10A	15.875 mm	10.16 mm	5.08 mm	9.40 mm	22.2 kN	0.98 kg/m	General industrial
#60	12A	19.05 mm	11.91 mm	5.94 mm	12.57 mm	31.8 kN	1.42 kg/m	Industrial drives, pumps
#80	16A	25.40 mm	15.88 mm	7.94 mm	15.75 mm	56.7 kN	2.56 kg/m	Heavy machinery, conveyors
#100	20A	31.75 mm	19.05 mm	9.53 mm	18.90 mm	88.5 kN	3.91 kg/m	Mining, heavy conveyors
#120	24A	38.10 mm	22.23 mm	11.10 mm	25.22 mm	127.0 kN	5.62 kg/m	Crushers, mills
#140	28A	44.45 mm	25.40 mm	12.70 mm	25.22 mm	172.4 kN	7.50 kg/m	Heavy industrial
#160	32A	50.80 mm	28.58 mm	14.27 mm	31.55 mm	226.8 kN	10.10 kg/m	Steel mills, quarries
#180	36A	57.15 mm	35.71 mm	17.46 mm	35.48 mm	280.2 kN	13.45 kg/m	Extra-heavy industrial
#200	40A	63.50 mm	39.68 mm	19.84 mm	37.85 mm	355.8 kN	16.60 kg/m	Bucket elevators
#240	48A	76.20 mm	47.63 mm	23.81 mm	47.35 mm	512.1 kN	24.00 kg/m	Oil rigs, mega conveyors
Bicycle 1/2×1/8	-	12.70 mm	8.51 mm	3.66 mm	3.18 mm	9.0 kN	0.38 kg/m	Single-speed bicycles
Bicycle 1/2×3/32	-	12.70 mm	7.75 mm	3.60 mm	2.38 mm	8.5 kN	0.31 kg/m	Multi-speed derailleur bikes
Motorcycle 520	-	15.875 mm	10.16 mm	5.24 mm	6.35 mm	31.8 kN	0.88 kg/m	Sport motorcycles
Motorcycle 525	-	15.875 mm	10.16 mm	5.24 mm	7.94 mm	35.6 kN	0.96 kg/m	Mid-weight motorcycles
Motorcycle 530	-	15.875 mm	10.16 mm	5.24 mm	9.53 mm	44.5 kN	1.15 kg/m	Heavy touring motorcycles

Frequently Asked Questions

A roller chain alternates between inner link plates and outer link plates. When the chain closes into a loop, an outer link must connect to an inner link. An even number of links ensures proper mating. An odd number forces the use of an offset (half) link, which has roughly 25% lower fatigue strength and is a common point of failure. Always round up to the next even integer.

Steel roller chain has a thermal expansion coefficient of approximately 11.7 × 10⁻⁶ mm/mm/°C. A 1000 mm chain heated from 20°C to 120°C elongates by roughly 1.17 mm. For most industrial drives this is negligible compared to wear elongation. For precision applications (cam timing, indexing), add thermal compensation to your center distance calculation.

ANSI standards recommend replacing a roller chain when it has elongated 3% beyond its nominal pitch for standard drives and 1.5% for precision or high-speed drives. Beyond this threshold, the chain will skip teeth on the sprockets. Measure elongation over 10 or more pitches for accuracy.

No. The standard two-sprocket formula assumes a taut chain on horizontal shafts. For vertical drives, add 2 links for catenary sag compensation. For horizontal spans exceeding 60 pitches, industry practice is to add 1 - 2% to the calculated length and use an adjustable idler or tensioner.

The recommended center distance is between 30 and 50 pitches. The absolute minimum is the sum of the sprocket radii plus clearance. The maximum practical limit is around 80 pitches; beyond this, chain whip and vibration become problematic. For optimal wrap angle, ensure the center distance produces at least 120° of wrap on the smaller sprocket.

The ANSI chain number divided by 8 gives the pitch in inches. For example, #40 chain has a pitch of 40 ÷ 8 = 5/8 inch = 12.70 mm. Exception: chains ending in 5 (e.g., #25, #35) are lightweight (cotterless) variants with the same pitch as their #20 and #30 counterparts but narrower plates.