Roller Chain Wear & Elongation Calculator
Measure a length of chain, enter it here, and see how far it has worn against the replacement limit for your drive. How to measure is below the calculator.
How to measure
| Step | What to do |
|---|---|
| 1. Make it safe | Stop the drive and lock it out before measuring a chain still on its sprockets. |
| 2. Pull it straight | Measure with the chain under light tension and lying straight, on the tight side of the drive. |
| 3. Count pitches | Measure from a point on one pin to the same point on a pin a counted number of pitches away. Use as many pitches as you can: at least 4, and a span of several feet gives a better average. |
| 4. Enter and compare | Enter the chain size, the number of pitches and the length. A tape, steel rule or calipers will do. |
How this is calculated
| Result | Formula |
|---|---|
| Nominal length | number of pitches × pitch |
| Elongation | (measured − nominal) ÷ nominal × 100 |
| Replacement limit | 3%, or 200 ÷ teeth on the largest sprocket when it has more than 66 teeth |
The 3% limit and the 200 ÷ N rule for large sprockets follow roller chain maintenance guidance from chain manufacturers, including Rexnord's chain elongation guide (2.5 to 3% for roller chain) and roller chain maintenance literature. Fixed-center drives with no adjustment may need replacing sooner. ANSI pitches per ASME B29.1. Results are a guide: follow your chain maker's limit where it differs.
Frequently asked questions
What is roller chain stretch?
It is wear, not stretching of the metal. As the pins and bushings wear, each pitch gets slightly longer, so the chain as a whole grows. A worn chain rides higher on the sprocket teeth and can skip or jump the sprocket.
When should roller chain be replaced?
For most drives, replace roller chain when it has worn 3 percent longer than new. Rexnord's guidance puts the limit at 2.5 to 3 percent. On drives where the largest sprocket has more than 66 teeth, the limit is 200 divided by the number of teeth, which is lower.
How do you measure chain elongation?
With the drive stopped and locked out, pull the chain straight under light tension and measure from a point on one pin to the same point on a pin a counted number of pitches away. Measure as many pitches as you can, at least four. Divide the difference from the nominal length by the nominal length.
Why is the limit lower with large sprockets?
The larger the sprocket, the less elongation it takes before the chain climbs the teeth. Dividing 200 by the tooth count gives the limit, so a 100-tooth sprocket allows only 2 percent.
Should I replace the sprockets with the chain?
Inspect them. Teeth that are hooked, worn thin or polished on one side will wear a new chain quickly, so replace worn sprockets with the chain. Never join new chain to a worn length.
Can Jealco supply roller chain and sprockets?
Yes. We supply ANSI roller chain and sprockets and can match an existing drive. Send us the chain number, the length or number of pitches, and the sprocket tooth counts and bores.
Related
Chain, sprockets and sheaves
Roller chain and sprockets for your drive.
Shaft torque and coupling calculator
Torque from HP and coupling sizing.
Gearbox ratio calculator
Ratio, output speed and torque.
All calculators
Conveyor, elevator and more.
Chain due for replacement?
Send us the chain number, length or number of pitches, and the sprocket sizes, and we will quote the chain and, if needed, the sprockets.